eigrp deployment

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1© 2005 Cisco Systems, Inc. All rights reserved.

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EIGRP Deployment

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EIGRP Deployment

• EIGRP Operation

• Topologies and Techniques

• Managing EIGRP



EIGRP Operation

333© 2003, Cisco Systems, Inc. All rights reserved.

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http://slidepdf.com/reader/full/eigrp-deployment 4/133444© 2005 Cisco Systems, Inc. All rights reserved.

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EIGRP Operation

• Neighbor Formation

• Computing Metrics

• The Diffusing UpdateAlgorithm

• The Active Process

• External RoutingInformation



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EIGRP Neighbor Formation

• EIGRP uses a three wayhandshake to prevent neighbor

formation along a unidirectionallink

• When A receives the firstmulticast hello from B, it places

B in the pending state, andtransmits a unicast update withthe initialization (init) bit set

• While B is in this state, A willnot send it any queries or routing information

A

B

m u l

t i c a s t h e l l o

u n i c a s t u p d a t e + i n i t

B

i n p e n

d i n g



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• When B receives this updatewith the init bit set, it sends an

update with the init bit set aswell

• The acknowledgement for A’sinitial update is piggybacked

onto this packet—it is never transmitted by itself

• There is no way for A to receivethe acknowledgement for itsinitial update without alsoreceiving B’s initial update

A

B

m u l



B

i n p e n

d i n g

u

n i c a s t u p d a t e

+ i n i t + a c k



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• Once the acknowledgement for its initial update is received, A

takes B out of the pendingstate, and begins sending ittopology information

• If this acknowledgement isn’t

ever received, hello’s from Bare ignored while A attempts toretransmit the initial update

• Eventually, A will time B out,and the process will start over

A

m u l



B

i n p e n

d i n g

u

n i c a s t u p d a t e

+ i n i t + a c k

B

o u t o f p e n d i n g

u n i c a s t t o p o l o g

y t a b l e i n f o

B



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• For each route A sends B, Bsends a poison reverse

• This makes certain the tworouter’s tables are accurate

• When a router finishes

sending its table, it sends anend-of-table indicator

A

u n i c a s t t o p o l o g

y t a b l e i n f o

p o i

s o n r e v e r s e u n

i c a s t r o u t e s

e n d - o f - t a b l e

B



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Computing Metrics

• EIGRP uses a compoundmetric

• Individual metrics are calledcomponent metrics

Five components:bandwidth, delay, load,

reliability, and MTUBy default, only bandwidthand delay are actually used

• Calculated metric is called

the composite metric

( )

256*

min

107

⎥

⎦

⎤⎢

⎣

⎡+∑delays

bandwidth



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( )

256*

min

107

⎥

⎦

⎤⎢

⎣

⎡+∑delays

bandwidth

( )256*

min

107

⎥⎦

⎤⎢⎣

⎡+∑delays

bandwidth

Computing Metrics

10.1.1.0/24

BW: 1000Delay: 100

BW: 100Delay: 1000

BW: 56Delay: 2000

A

B

C

Minimum

Added Together

• Router A advertises 10.1.1.0/24to B

Bandwidth is set to 1000Delay is set to 100

• Router B

Compares current bandwidth to

bandwidth of link to A; setsbandwidth to 100

Adds delay along link to A, for atotal of 1100

• Router C

Compares current bandwidth tobandwidth of link to B; setsbandwidth to 56

Adds delay along link to B, for a

total of 3100



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Computing Metrics

• Router C uses the formula tocompute a composite metric

This isn’t what the router computes, though—why?

The router drops the remainder after the first step!

• Why the 256?

EIGRP uses a 32 bit metricspace

IGRP uses a 24 bit metric space

To convert between the two,multiply or divide by 256!

( )256*

min

107

⎥⎦

⎤

⎢⎣

⎡+

∑delays

bandwidth

46507885256*3100

56

107

=

⎥⎦

⎤

⎢⎣

⎡+

??

46507776256*310017857

17857156

107

=+

⎟⎟

⎠

⎞⎜⎜

⎝

⎛ =




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Computing Metrics

• Where does EIGRP get the component metrics?

Bandwidth: interface level bandwidth command

Delay: interface level delay command

Reliability: per interface computed reliability, 0-255

Load: per interface computed load, 0-255

• Why not set the K values so the reliability and load are pickedup?

Interface level computed metrics are only picked up when achange in the bandwidth or delay causes EIGRP to reread them

Effectively, this means these metrics are never changed, onceEIGRP forms its initial neighbor adjacency across the interface




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The Diffusing Update Algorithm (DUAL)

• How does EIGRP determinewhich routes are loop free?

• Each of A’s neighbors isreporting reachability to E:

B with a cost of 10

C with a cost of 10

D with a cost of 30

• These three costs arecalled the reporteddistance (RD); the distanceeach neighbor is reporting toa given destination

A

B

C

D

E

10

10 30

10 15

15




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• At A, the total cost toreach E is:

20 through B

25 through C

45 through D

• The best of these threepaths is the path through B,with a cost of 20

• This is the feasible distance(FD)

A

B

C

D

E

10

10 30

10 15

15




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• A uses these two pieces of information to determinewhich paths are loop free

• The best path (FD) is used asa benchmark; all paths withRDs lower than the FDcannot contain loops

• The algorithm may marksome loop free paths as loops

• However, it is guaranteednever to mark a looped path as

loop free

A

B

C

D

E

10 30

10 15

15

10




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• At A:

The path through B is the

best path (FD), at 20

C can reach E with a costof 10; 10 (RD) is less than20 (FD), so this path is

loop free

D can reach E with a costof 30; 30 (RD) is not lessthan 20 (FD), so EIGRP

assumes this path is a loop

A

B

C

D

E

10

10 30

10 15

15




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• If the best path fails, throughB (the successor), EIGRP

will examine the availablepaths to E

• Finding a path which waspreviously declared loop

free (a feasible successor),it begins using itimmediately

• C now becomes thesuccessor (best path)

A

B

C

D

E

1010

10 15

15

30




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• Are there any FeasibleSuccessors from Router E’sperspective?

FD is 20

RD from C is 15

RD from D is 15

RD < FD, so it satisfies theFeasibility Condition (FC)

We have two FS!

• In order for there to be onlyone FS, the link A-D or A-Cwould need to be increasedto at least 20.

A

B

C

D

E

1010

10 15

15

30




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• A now examines itstopology

information based on thenew successor metric

• The reported distancethrough the remaining

neighbor, D, is 30;30 (RD) is still more than25 (FD), so this path is stillconsidered a loop

A

B

C

D

E

1010 30

10 15

15




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• The path through C nowfails

• A examines its topologyinformation, and finds ithas no loop free path to E

• However, it does have

a neighbor, and thatneighbor might have aloop free path

• So, it places E in active

state and queries D

A

B

C

D

E

1010 30

10 15

15




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• D examines its topologyinformation

• Since its best path is notthrough A, the path it hasto E is still valid

• D sends a reply to this

query, indicating it still hasa valid loop free path to E

• Once A receives this reply, itbegins using the path

through D

A

B

C

D

E

1010 30

10 15

15




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The Active Process

• Enhanced Active Processing

12.1(4.0.3)T and 12.1(4.1)

• So what used to happen whenA loses its route to 10.1.1.0/24?

No FS, mark route active

Set a 3 minute active timer

Query all neighbors (B)

• B receives A’s query

No FS, mark route active

Set 3 minute active timer

Query all neighbors (C)

• C receives B’s query

Examine local topology table

No feasible successors

No neighbors to query!

A

B

C

10.1.1.0/24

10.1.10/24 Gone; No FS

Query

Query

10.1.10/24 Gone; No FS

10.1.10/24 Gone




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The Active Process

• C has no alternate path to10.1.1.0/24

Remove from local tablesReply to querying neighbors

• B receives C’s reply

No outstanding queries

Remove from local tables

Reply to querying neighbors

• A receives B’s reply

No outstanding queries

Remove from local tables

A

B

C

10.1.1.0/24

10.1.10/24 Gone; No FS

Query

Query

10.1.10/24 Gone; No FS

10.1.10/24 Gone

Reply

Reply

Remove 10.1.1.0/24

Remove 10.1.1.0/24

Remove 10.1.1.0/24




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The Active Process

• If C sends the reply, and Bnever receives it, whathappens?

• A’s active timer (3 minutes) isstill counting down while Band C are trying to get thereply back

• When this timer expires, Adeclares an SIA

The A/B neighbor relationship isreset

Why reset A/B when B/C is the

problem??

A

B

C

10.1.1.0/24

10.1.10/24 Gone; No FS

Query

Query

10.1.10/24 Gone; No FS

10.1.10/24 Gone

Reply

Remove 10.1.1.0/24

Bad Link, ReplyNever Makes It

Reset Relationship!




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The Active Process

• Active Process Enhancement

12.1(4.0.3)T and 12.1(4.1),CSCdp33034

So NOW what happens?

• A queries B when the route goesaway. Then A sets a sia-retransmittimer to half the configured active

time (1.5 minutes, normally)• After this time has passed, A sends

an SIA Query

If B acknowledges this SIA query, A resetsits timer, and the A/B neighbor relationship

stays up.

A will send the sia-retransmit 3x, for a totalwindow of 4.5 minutes. Even if B replies,after 3 tries A will reset the neighbor relationship A/B.

A

B

C

10.1.1.0/24

10.1.10/24 Gone; No FS

Query

SIA Query




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The Active Process

A

B

C

10.1.1.0/24

10.1.10/24 Gone; No FS

Query

Query

10.1.10/24 Gone; No FS

10.1.10/24 Gone

Reply

Remove 10.1.1.0/24

Bad Link, ReplyNever Makes It

SIA Query

• C will either reply to the query,which B will then clear back to A,

or C will fail to reply at some pointand B will reset its relationshipwith C.

• Either event clears the query fromB’s point of view, which is thencleared back to A minimizing SIA’sconsiderably.

• If anything gets reset, its now the“right” neighbor adjacent to the

problem router, helping totroubleshoot and identify problemrouters easier.




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The Active Process

10.1.1.0/24

A B

C

D

E

• Where does the query stop?

• Router A loses its connection

to 10.1.1.0/24Router A does not consider B aFS, for some reason

Router A sends B a query

• Router B examines its localtables, and finds:

Its current path (successor)doesn’t pass through A

It has a FS that doesn’t passthrough A

• Router B answers

The query is bounded wherethere is local knowledge of

another loop-free path

Localknowledge of an alternatepath, so reply

G

F




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The Active Process

10.1.1.0/24

A B

C

D

E

• Router C is filtering 10.1.1.0/24towards D

• Router A loses its connectionto 10.1.1.0/24

Router A sends C a query

• Router C has no FS for 10.1.1.0/24

Router C sends D a query

• Router D examines its localtables

No information about10.1.1.0/24, so send a reply

Query is bounded because Dhas no information about10.1.1.0/24


F i l t e r

G

No knowledgeof route, soreply

F




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The Active Process

10.1.1.0/24

A B

C

D

E

F

• Router E is summarizingtowards F

• Router A loses its connectionto 10.1.1.0/24

Router A sends E a query

• Router E has no FS for 10.1.1.0/24

Router E sends F a query

• Router F examines its localtables

No information about10.1.1.0/24, so send a reply

Query is bounded because Fhas no information about10.1.1.0/24

G


F i l t e r


S u m m a r y





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The Active Process

10.1.1.0/24

A B

C

D

E

F

• Router G has no neighbors

• Router A loses its

connection to 10.1.1.0/24

Router A sends G a query

• Router G examines its local

tablesNo FS

No neighbors to query, sosend a reply

G


F i l t e r


S u m m a r y


No neighbors,so reply




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The Active Process

10.1.1.0/24

A B

C

D

E

F

• The Query is bounded by:

Local knowledge of an

alternate loop-free path notlearned through theneighbor the query wasreceived from

No local knowledge of theroute because of filtering or summarization

No neighbors to query G


F i l t e r


S u m m a r y


No neighbors,so reply




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External Routing Information

• What is an External Route in EIGRP?

• Any route within EIGRP that originated outside of the

EIGRP process.Basically, routes redistributed into EIGRP from another protocol, static, or connected routes.

Marked in the routing table as D EX to indicate EIGRP owns

the route but that it was originated external to EIGRP.

router# show ip route

[snip…]

D EX 20.1.1.0 [170/2560025856] via 10.1.1.4, 00:07:26, FastEthernet0




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• What additional information is carried in an external?

Router# show ip eigrp topo 172.31.1.98 255.255.255.255

IP-EIGRP topology entry for 172.31.1.98/32

State is Passive, Query origin flag is 1, 1 Successor(s), FD is28160

Routing Descriptor Blocks:

0.0.0.0, from Redistributed, Send flag is 0x0

Composite metric is (28160/0), Route is External

Vector metric:

Minimum bandwidth is 100000 Kbit

Total delay is 100 microsecondsReliability is 255/255

Load is 1/255

Minimum MTU is 1500

Hop count is 0

External data:

Originating router is 172.31.4.100 (this system)

AS number of route is 1

External protocol is OSPF, external metric is 0

Administrator tag is 150 (0x00000096)

Originating Router ID

AS #

Protocol of Origin

External Metric

Admin Tags




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Administrative Distances

Route Source Default Distance ValuesConnected interface 0

Static route 1

EIGRP summary route 5

eBGP 20

Internal EIGRP 90

IGRP 100

OSPF 110

(IS-IS) 115RIP 120

On Demand Routing (ODR) 160

External EIGRP 170

iBGP 200

Unknown 255

• Why is the administrativedistance higher on anexternal?

To prefer Internal EIGRProutes over EIGRPExternals

To prefer routinginformation originatingwithin our AS over thatwhich originatedsomewhere outside our

control



Topologies and Techniques

353535© 2003, Cisco Systems, Inc. All rights reserved.11050_05_2005_X2




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Topologies and Techniques

• Hub and Spoke Design

• EIGRP Stubs

• EIGRP PE-CE

• Redundancy

• Load Sharing• Fast Convergence

• Using Bandwidth

• Redistribution

• Multiple AS




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Hub and Spoke Design

interface s0/0

ip address 10.1.1.1 255.255.255.0• Hub and spoke networks are

often built over point-to-multipoint networks

• If the hub is configured to treatthe entire point-to-multipointnetwork as a single interface, itcan transmit multicast and

broadcast packets which arereceived by all spoke routers

• Layer 3 on the hub router willnot notice a single circuit

failure

packets transmittedhere are received by

all spokes

packets transmitted

here are received

only by the hub router




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• The hub router can also beconfigured to treat each

spoke’s circuit as anindividual point-to-pointcircuit on a subinterface

• If end-to-end signaling is in

use, a failed circuit willcause the subinterface tofail

packets

transmitted

here are receivedby one spoke

packets transmitted

here are received

only by the hub router

i nt er f ace s0/ 0. 1 poi nt - t o- poi nti p addr ess 10. 1. 1. 0 255. 255. 255. 254. . . .

i nt er f ace s0/ 0. 2 poi nt - t o- poi nti p addr ess 10. 1. 1. 2 255. 255. 255. 254. . . .

i nt er f ace s0/ 0. 3 poi nt - t o- poi nti p addr ess 10. 1. 1. 4 255. 255. 255. 254

i nt er f ace s0. 1 poi nt - t o- poi nti p addr ess 10. 1. 1. x 255. 255. 255. 254. . . .




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• In single homed hub andspoke networks, the hub

router, spoke routers, andthe links themselves are allsingle points of failure

You can mitigate the single

point of failure in the routersusing high availabilitytechniques

highly

available

S




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0.0.0.0/0

summary

only

1 9 2 .

1 6 8

. 0 . 0

/ 3 1

1 9 2 . 1 6 8 . 0 . 2 / 3

1

1 9 2 . 1 6 8 . 0

. 4 / 3 1

192.168.1.0/24

192.168.2.0/24192.168.2.0/24

access- l i st 10 deny 192. 168. 0. 0 0. 0. 0. 255access- l i st 10 per mi t any. . . .r out er ei gr p 100di str i but e- l i st 10 out

• Summarize towards the core

Number the remote links out of the same address space as the

remote networks, if possible

Use /31’s to conserve addressspace for point-to-points

• Send the remotes a default only

• If you can’t address the linksout of the summary addressspace, then use a distribute listto filter them from beingadvertised back into the core of the network

H b d S k D i




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• All the same principles apply todual homed hub and spokenetworks

Summarize or filter the links tothe remotes

Use /31’s on point-to-points toconserve address space

• Provide as little information aspossible to the remotes

Something more than a defaultroute may be required toprovide optimal routing

• Avoid Summary Black Holes!

0.0.0.0/0

summary

only

192.168.1.0/24

192.168.2.0/24

192.168.2.0/24

H b d S k D i




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• How do we limit the amount of information passed down to theremote sites?

• You can summarize at A and Btowards the remote routers

The summary will generate alocal route with anadministrative distance of 5

The external default routelearned from D will have anadministrative distance of 170

What happens?

Internet

EIGRP

A B

C

Dexternal

default

route

D* 0.0.0.0/0 is a summary,

00:08:41, Null0

ip summary-address eigrp 1

0.0.0.0 0.0.0.0

H b d S k D i




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• In this case, the locallygenerated discard route wins

The route learned from D will

not be installed in the local table

Hosts behind C will not be ableto reach destinations on theInternet

• There are ways to prevent thisdiscard route from beinginstalled, but we need to becareful with the design

Routing Loops

Routing Black Holes

There is enough rope here tohang yourself!

D* 0.0.0.0/0 is a summary,

00:08:41, Null0

ip summary-address eigrp 1

0.0.0.0 0.0.0.0

Internet

EIGRP

A B

C

Dexternal

default

route

H b d S k D i




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• If two routing protocols providea route to the same destination,how do we choose between

them?Their metrics are notcomparable

An administrative distance isadded to each route learnedbased on the protocol installingthe route

• Static routes can be configuredwith a distance

This can create a floating static

The route will not be usedunless the dynamic protocolshave no route to that destination

r out er #show i p ei gr p t opol ogyP 10. 0. 1. 0/ 24, 1 successors, FD i s 2681856

vi a 10. 1. 1. 1 ( 2681856/ 2169856)

r out er ( conf i g) #i p r out e 10. 0. 1. 0255. 255. 255. 0 nul l 0

r out er ( conf i g) #i p r out e 10. 0. 1. 0

255. 255. 255. 0 nul l 0 200

distance 90

distance 1

distance 200

the static

route wins

the EIGRProute wins





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• The route generated by thesummary is called a discardroute

• What would happen if this routeisn’t created?

Configure two routers back toback with overlappingsummaries

Generate a packet towards10.1.2.1 from either router

At A, the best path is through10.1.0.0/16 to B

At B, the best path is through10.0.0.0/8 to A

Routing Loop

1 0 . 0 . 0 . 0 / 8

1 0 . 1 . 0 . 0

/ 1 6

ip summary-address eigrp 1 10.0.0.0

255.0.0.0


255.255.0.0

10.1.1.0/24

10.2.1.0/24

A

B

10.1.2.1





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• To remove the discard route

In EIGRP, add an administrativedistance after the ip summary

address command

In OSPF, use the command nodiscard-route under the routingprocess

• What happens if A loses its pathto D?

C will now prefer the internallearned through A over theexternal learned trough B

We have a black hole


0.0.0.0 200

D* 0.0.0.0/0 [170/409600] via <A>

[170/409600] via <A>

external

default

route

D* 0.0.0.0/0 [90/409600] via <A>

[90/409600] via <A>

Internet

EIGRP

A

C

D

B





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access- l i st 10 per mi t host 0. 0. 0. 0access- l i st 20 deny host 0. 0. 0. 0access- l i st 20 per mi t any. . . .i p r out e 0. 0. 0. 0 0. 0. 0. 0 nul l 0 250

. . . .r out er ei gr p 100redi s t r i but e s tat i cdi st r i but e- l i st 10 out <r emot e 1>di st r i but e- l i st 10 out <r emot e 2>di st r i but e- l i st 10 out <r emot e 3>

di st r i but e- l i st 20 out <cor e>

• You can also use floating staticroutes at the two hub routersand redistribute them into the

routing protocolDistribute list 10 only allows thedefault route to be advertised tothe remotes

Distribute list 20 prevents a

default route from being leakedback into the core

• This has the same problem if asingle link back towards thecore and the injected externalroute both fail

There are other situations under which this also fails

A

C

B





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• One solution is to have a linkbetween the summarizingrouters across which they

share full routing information• Conditional advertisement of

routing information is another possible solution

OSPF can conditionally generate adefault route

EIGRP has conditionaladvertisement as a plannedfeature

full routing information

Internet

EIGRP

A B

C

Dexternal

default

route





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• EIGRP can run over either amultipoint interface at the hubrouter or point-to-point

subinterfacesA single multipoint interface iseasier to configure but it can beharder to troubleshoot

P2P subinterfaces allow for

more granular failure detection.

• Use summarization at the hubrouters to reduce informationinto the network core

• Provide as little information tothe remotes as possible

Declare the remote routers asstubs

0.0.0.0/0

summary

only

192.168.1.0/24

192.168.2.0/24

192.168.2.0/24

single multipoint

or several

point-to-points

r out er ei gr p 100

ei gr p st ub connect ed. . . .

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• When a router runningEIGRP loses its connectionto a network, it firstsearches for alternate loopfree paths

• If it finds none, it then sends

queries to each of itsneighbors, looking for analternate path

BA

1 0 . 1 . 1 . 0

/ 2 4

router-a#sho ip eigrp topo

IP-EIGRP Topology Table....

P 10.1.1.0/24, 1 successors, FD is 281600

via Connected, Ethernet1/2

router-a#show ip eigrp eventsEvent information for AS 100:

....

12 Active net/peers: 10.1.1.0/24 1

14 FC not sat Dmin/met: 4294967295 128256

15 Find FS: 10.1.1.0/24 128256

....18 Conn rt down: 10.1.1.0/24 Ethernet 3/1

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• If the neighbor has no path tothis destination, it replies

• The router then removes allreferences to this route from itslocal tables

• In large hub and spoke

networks, the hub routers haveto build queries and processreplies from each of the spokes

• This impacts scaling!

router-a#show ip eigrp events

Event information for AS 100:1 NDB delete: 10.1.1.0/24 1

....

12 Active net/peers: 10.1.1.0/24 1

14 FC not sat Dmin/met: 4294967295 128256

15 Find FS: 10.1.1.0/24 128256

....

18 Conn rt down: 10.1.1.0/24 Ethernet 3/1

BA

1 0 . 1 . 1 . 0

/ 2 4

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• If these spokes are remotesites, they have twoconnections for resiliency, not

so they can transit trafficbetween A and B

• A should never use the spokesas a path to anything, so

there’s no reason to learnabout, or query for, routesthrough these spokes

BA

1 0 . 1 . 1 . 0

/ 2 4

don’t use these paths

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• To signal A and B that the pathsthrough the spokes should notbe used, the spoke routers can

be configured as stubs

router#config trouter(config)#router eigrp 100

router(config-router)#EIGRP stub connected

router(config-router)#

BA

1 0 . 1 . 1 . 0

/ 2 4

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• Marking the spokes as stubsallows them to signal A and Bthat they are not valid transit

paths

• A will not query stubs,reducing the total number of queries in this example to 1

• Marking the remotes as stubsalso reduces the complexity of this topology; B now believes itonly has 1 path to 10.1.1.0/24,

rather than 5

m a r k e

d a s

s t u b s

BA

1 0 . 1 . 1 . 0

/ 2 4

EIGRP Stubs




RST-3221

11050_05_2005_X2

EIGRP Stubs

• If stub connected isconfigured

B will advertise 10.1.2.0/24

to A

B will not advertise10.1.2.0/23, 10.1.3.0/24, or 10.1.4.0/24

• If stub summary isconfigured

B will advertise 10.1.2.0/23to A

B will not advertise

10.1.2.0/24, 10.1.3.0/24, or 10.1.4.0/24

ip route 10.1.4.0 255.255.255.0 10.1.1.10

!

interface serial 0

ip summary-address eigrp 100 10.1.2.0 255.255.254.0

!

router eigrp 100redistribute static 1000 1 255 1 1500

network 10.2.2.2 0.0.0.1

network 10.1.2.0 0.0.0.255

10.1.2.0/24

A

B

10.2.2.2/31

1 0 . 1 . 3 . 0 / 2

4

eigrp stub connected

eigrp stub summary

EIGRP Stubs




RST-3221

11050_05_2005_X2

G Stubs

• If stub static is configured

B will advertise 10.1.4.0/24to A

B will not advertise10.1.2.0/24, 10.1.2.0/23, or 10.1.3.0/24

• If stub receive-only isconfigured

B won’t advertise anythingto A, so A needs to have astatic route to the networks

behind B to reach them

A

10.2.2.2/31

B

1 0 . 1 . 3 . 0 / 2

4

10.1.2.0/24

ip route 10.1.4.0 255.255.255.0 10.1.1.10

!

interface serial 0

ip summary-address eigrp 10.1.1.0 255.255.254.0

!

router eigrp 100redistribute static 1000 1 255 1 1500

network 10.2.2.2 0.0.0.1

network 10.1.2.0 0.0.0.255

eigrp stub static

eigrp stub receive-only

EIGRP Stubs




RST-3221

11050_05_2005_X2

• Any combination of the route types can be specified on theeigrp stub statement, except receive-only, which cannot be

used with any other option• For example:

eigrp stub connected summary redistributed

• If eigrp stub is specified without any options, it will actuallyenable eigrp stub connected summary.

• Use the stub cli options as well as other filtering techniquesto fine tune the amount of information advertised to stub

routers.

EIGRP Stubs




RST-3221

11050_05_2005_X2

• At A, you can tell B is a stubusing show ip eigrpneighbor detail.

10.1.2.0/24

B

A

10.2.2.2/31

1 0 . 1 . 3 . 0

/ 2 4

router-a#show ip eigrp neighbor detail

IP-EIGRP neighbors for process 100

H Address Interface Hold Uptime SRTT RTO Q Seq Type

(sec) (ms) Cnt Num

0 10.2.2.3 Et1/2 10 00:00:50 320 1920 0 7

Version 12.2/1.2, Retrans: 0, Retries: 0

Stub Peer Advertising ( CONNECTED ) Routes

EIGRP PE/CE Deployment




RST-3221

11050_05_2005_X2

p y

Service Provider

Site 1

Site 2

A

B

C

D

VPN

External

• Similar to Hub and Spoke insome ways (high neighbor count)

• In this network, we have twocorporate sites, connectedby a leased line and VPNthrough a service provider

• EIGRP routes redistributedinto BGP at B, and back intoEIGRP at C, appear asexternal routes at Site 2

We want them to appear asinternal routes





RST-3221

11050_05_2005_X2

p y

Service Provider

Site 1

Site 2

A

B

C

D

VPN

Internal

• As routes are redistributedinto BGP at B, extendedcommunities containing the

EIGRP metrics are attachedto them

• As routes are redistributedback into EIGRP at C, these

extended communities areused to reconstruct theroutes as internals

• The VPN is considered a 0

cost link in this configuration





RST-3221

11050_05_2005_X2

Service Provider

Site 1

Site 2

A

B

C

D

VPN

Internal

ip vrf VRF-RED

rd 172.16.0.1:20

exit

....router eigrp 1

address-family ipv4 vrf VRF-RED

autonomous-system 101

network 172.16.0.0 255.255.0.0

redistribute BGP 101 metric 10000 100 255 1 1500

exit-address-family

router-c#show ip eigrp vrf VRF-RED topologyIP-EIGRP Topology Table for AS(1)/ID(192.168.10.1)

Routing Table:VRF-PINK


via 50.10.10.2 (409600/128256), Ethernet3/0






RST-3221

11050_05_2005_X2

No Backdoor Link

Service Provider

Site 1

Site 2

A

B

C

D

VPN

• 12.0(27)SV 12.0(21.1)SY212.0(21.1)S2

• Backdoor links are notsupported

• http://www.cisco.com/en/US/products/sw/iosswrel/ps183

9/products_feature_guide09186a0080154db3.html

EIGRP PE/CE Backdoor Links

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080154db3.html











RST-3221

11050_05_2005_X2

Service Provider

Site 1

Site 2

VPN

• The biggest danger with backdoor links is possible routing loops

Site1 advertises a network through theback door to site 2

C prefers this route, and redistributes itinto BGP

B prefers the BGP route, andredistributes it into EIGRP,forming a loop

• The solution is to automatically tagall the routes originatingin site 1 so they will berejected by C

• This tag is called the Site of

Origin (SoO)

A

B

C

D





RST-3221

11050_05_2005_X2

Service Provider

Site 1

Site 2

A

B

C

D

VPN

route-map SoOrigin permit 10

set extcommunity soo 100:1

....

interface FastEthernet 0/0

ip vrf sitemap SoOrigin

....

• The SoO is set on all PE routers onthe interface connecting to the PE,and on backdoor link routers

• The CE will always reject themarked EIGRP learned routes, andprefer the BGP learned routes

• You can then set the backdoor linkso the path through the VPN isalways preferred over the backdoor link





RST-3221

11050_05_2005_X2

• 12.0(27)SV 12.0(26)SZ 12.0(26.1)S

• http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a00801eff60.html

EIGRP PE/CE Prefix Limits

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a00801eff60.html







RST-3221

11050_05_2005_X2

• Generic redistribution— tolimit the number of redistributed routes/ prefixes

• MPLS VPN PE-CE—to limitthe number of prefixes on agiven PE router as follows:

For the whole VPN or

For individual CEs/neighbors

B G P / M P L S V P N

w ith E IG R P be tw e e n P E-C E

P E

C E

C E

C EC E

C E

C E

C E

C E

C E

C E

C E

C EC E

C E

C E

C E

P E

P E

P E

P E

V R F 1

V R F 2

V R F 3 V R F L +1V R F L

…

PE 1

Red1

R e d 2

neighbor maximum-prefix <maximum> [<threshold>] [warning-only] [[restart <restart

interval>][restart-count <count>][reset-time <reset interval>][dampened]]

redistribute maximum-prefix <maximum> [<threshold>] [warning-only][[restart <restart interval>]

[restart-count<count>

] [reset-time<reset interval>

][dampened]]


RST-3221

11050_05_2005_X2

EIGRP PE/CE Prefix Limits




RST-3221

11050_05_2005_X2

• 12.0(29)S 12.3T in progress, 12.2S planned

• DDTS: CSCeb02607

Redundancy






RST-3221

11050_05_2005_X2

• There are several reasons for redundancy in anetwork:

To provide multiple attachment points for servers andhosts in case of a link or device failure

To provide alternate links through the network in case of

link or device failureTo provide optimal routing to services

To provide load sharing in heavily utilized areas

Redundancy




RST-3221

11050_05_2005_X2

• It’s common to buildnetworks with back-to-backrouters for redundancy

• The routing protocol seeseach of these links as apossible transit path, soeach link adds another set

of paths the routing protocolmust consider whencalculating the best path

• You want to route to these

links, not through themRP Transit

Paths

HSRP peers

Redundancy




RST-3221

11050_05_2005_X2

• The solution to this is passive-interface.

• Configuring an interface as

passive in EIGRP, OSPF, or IS-IS will cause it not to formneighbor relationships acrossthe link.

• These networks will still beadvertised as reachabledestinations, but they will never be advertised as transit links.

router eigrp 100

passive-interface fastethernet 0/0



passive-interface fastethernet 0/3....

router eigrp 100

passive-interface default

no passive-interface fastethernet 1/0....

-or-

Redundancy




RST-3221

11050_05_2005_X2

backup path

optimal routing

additional bandwidth

• It’s common to build outalternate links in a network

Adds network resiliency

Can provide optimal routing toresources

Adds additional bandwidth incongested areas of the network

• The second link also addsmoderate complexity, and moreinformation, into the network

Redundancy




RST-3221

11050_05_2005_X2

• Adding a third link almostalways approaches the point of diminishing returns, and addsmuch more network complexity

• When considering adding moreredundancy, always balance theincreased resiliency against theadded complexity

Increased network convergencetimes

Increased management effort

Increased troubleshooting times

Redundancy




RST-3221

11050_05_2005_X2

2.5

0 10000

s e c o n d s

routes

feasible successor

• The impact of greater levelsof redundancy onconvergence times can be

seen in routing protocolscalability testing.

• Using EIGRP, with a single

backup path, it takes about1.3 seconds for a router with10000 routes to convergewhen the best path fails.

best path

fails

Redundancy




RST-3221

11050_05_2005_X2

2.5

0 10000

s e c o n d s

routes

• Adding the third pathincreases convergence timeto 2 seconds.

• Adding the fourth pathincreases convergence timeto 2.25 seconds.

best path

fails

Redundancy




RST-3221

11050_05_2005_X2

• High availability studies alsoshow the impact of adding thethird link is not all that great

Adding a second link willincrease reliability significantly

Adding a third link approachesthe point of diminishing returns

• Combined with the impact of slower convergence times,higher management costs, andslower troubleshooting, thetotal downtime in a networkmay actually increase with theaddition of large amounts of redundancy

99.50

99.60

99.70

99.80

99.90

100.00

1 link 2

links

3

links

4

links

r e l i a b i l i t

y

Redundancy




RST-3221

11050_05_2005_X2

• If you’re adding more linksto increase the availablebandwidth in a specific

place in the networkTry to hide this complexityfrom other parts of thenetwork, if possible

Summarize just the parallellinks into a singleadvertisement at both sidesif you’re using a distancevector protocol

summary

summary

Redundancy




RST-3221

11050_05_2005_X2

• Layer 2 bundling (suchMLPPP or Etherchannel)may be useful to reduce the

layer 3 complexity whenusing multiple links to buildrequired bandwidth

• But be careful of issues withprocessor utilization due tobundling overhead,troubleshooting complexity,etc

link bundle

Redundancy




RST-3221

11050_05_2005_X2

• Consider using HighAvailability (HA) techniquesto reduce overlapping

redundancy.

• Stateful Switchover/NonStopForwarding with redundant

hardware in the same boxmay be able to replaceredundant connections tonetwork connected devices.

single high

availability device

Redundancy




RST-3221

11050_05_2005_X2

• Balance between complexityand resiliency

• Hide the additional complexitycreated by redundant linkswhere possible

Summarization

Link bundling (but balanceagainst overhead)

• Consider High Availabilitytechniques to reduce heavyredundancy for resiliency

99.50

99.60

99.70

99.80

99.90

100.00

1 link 2

links

3

links

4

links

r e l i a b i l i t y

GR/NSF Fundamentals




RST-3221

11050_05_2005_X2

• NonStop Forwarding (NSF) is a way to continue forwardingpackets while the control plane is recovering from a failure

• Graceful Restart (GR) is a way to rebuild forwardinginformation in routing protocols when the control plane hasrecovered from a failure

• The fundamental premise of NSF/GR is to route through

temporary failures, rather than around them!

EIGRP Graceful Restart/NSF




RST-3221

11050_05_2005_X2

• Router A loses itscontrol plane for someperiod of time

• It will take some timefor Router B torecognize this failure,

and react to it• Thus, this feature is

incompatible with FastHellos

Control Data A

Control Data B





RST-3221

11050_05_2005_X2

• During the time that A hasfailed, and B has notdetected the failure, B will

continue forwarding trafficthrough A

• Once the control planeresets, the data plane will

reset as well, and this trafficwill be dropped

• NSF reduces or eliminatesthe traffic dropped while A’s

control plane is down

Control Data

reset

A

Control Data B





RST-3221

11050_05_2005_X2

• If A is NSF capable, thecontrol plane will not resetthe data plane when it

restarts

• Instead, the forwardinginformation in the data planeis marked as stale

• Any traffic B sends to A willstill be switched based onthe last known forwarding

information

Control Data

No Reset

A

Control Data

Mark Forwarding

Information as Stale

B





RST-3221

11050_05_2005_X2

• While A’s control plane isdown, the routing protocol holdtimer on B counts down…

• A has to come back up andsignal B before B’s hold timer expires, or B will route around it

• When A comes back up, itsignals B that it is stillforwarding traffic, and wouldlike to resync

• This is the first step in GracefulRestart (GR)

Hold Timer: 1514131211109876

Control Data A

Control Data B





RST-3221

11050_05_2005_X2

• The signal in EIGRP is anupdate with the initializationand restart (RS) bits set

• A sends its hellos with therestart bit set until GR iscomplete

• B transmits the routinginformation it knows to A

• When B is finished sendinginformation, it sends a specialend of table signal so A knowsthe table is complete

Control Data

Control Data

A

B

t o p o l o g y

i n f o r m a t i o n

h e

l l o + R e s t a r t

i

n i t + R e s t a r t

e n d o f t a b l e





RST-3221

11050_05_2005_X2

• When A receives this end of table marker, it recalculates itstopology table, and updates

the local routing table

• When the local routing table iscompletely updated, EIGRPnotifies CEF

• CEF then updates theforwarding tables, andremoves all information

marked as stale

Control Data A

Control Data B





RST-3221

11050_05_2005_X2

• eigrp nsf enables gracefulrestart

• show ip protocols verifiesgraceful restart isoperational

• http://www.cisco.com/en/US/

products/sw/iosswrel/ps1839/products_feature_guide09186a0080160010.html

Arouter eigrp 100

eigrp nsf

....

router eigrp 100

eigrp nsf

....

router#show ip protocols

Routing Protocol is "eigrp 100“....

Redistributing: eigrp 100

EIGRP NSF-aware route hold timer is 240s

Automatic network summarization is in effect

Maximum path: 4

....

B


http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080160010.html











RST-3221

11050_05_2005_X2

• Routing protocol graceful restart is supported in IOS 12.2(15)T

• NonStop Forwarding is supported on the:

Cisco 10000 and Cisco 12000 12.0(22)SCisco 7500 in 12.0(22)S, with the caveat that inserting a new standby RSPwill cause some traffic loss, and switching from the primary to standbyRSP will cause a microcode reload on theline cards

Cisco 7600/6500 12.2(18)SXD

• http://www.cisco.com/en/US/partner/tech/tk826/tk364/technologies_white_paper09186a008016317c.shtml

Unequal Cost Load Sharing

http://www.cisco.com/en/US/partner/tech/tk826/tk364/technologies_white_paper09186a008016317c.shtml







RST-3221

11050_05_2005_X2

• Can you load shareacross the two available

paths between A and D,even though they are notequal cost?

• Yes, using variance,as long as the pathsare loop free

A

B C

D

56K 56K

500K 1000K





RST-3221

11050_05_2005_X2

• D through CDistance: 560128Reported Distance: 557568

• D through BDistance: 1069568Reported Distance: 557568

• The best path is through C, soC is the successor

• The reported distance throughB is lower than the best path throughC, so this path is loop free

• B is the feasible successor (FS) 56K

2000ms

A

B C

D

56K

2000ms

56K2000ms

1000K10ms





RST-3221

11050_05_2005_X2

• Configure variance on router A with a value high enoughto include both paths

• Variance is a multiplier,so it has to be some number which, when multiplied bythe lower metric, is higher than the highest metricyou want to include in theload sharing

A

B C

D

Distance1069568

Distance560128





RST-3221

11050_05_2005_X2

• In this case, 560128 x 2 =1120256, which is higher than 1069568, so 2 will

work as the variance• router-a(config)#router eigrp 100

router-a(config-rtr)#variance 2router-a(config-rtr)#end

A

B C

D

Distance1069568

Distance560128

Lowest metric is greater

than half of highest metric





RST-3221

11050_05_2005_X2

• Both paths are installedin the routing table

• The higher metric is then

divided by each lower metric to determine theload share count

• 1069568/560128≈2

• So, the load share on thepath through C will be setto 2, and the load share onthe path through B willbe set to 1

A

B C

D

Distance1069568

Distance560128





RST-3221

11050_05_2005_X2

• From this point, the actual loadsharing of traffic is up to theswitching engine being used to

forward packets

• For process switching, each packetforwarded through B will matchedby two packets forwarded throughC

A

B C

D

Distance1069568

Distance560128

Load Share 1

Load Share 2

EIGRP Fast Convergence




RST-3221

11050_05_2005_X2

• Already a standard part of EIGRP

• Customers have been using EIGRP to achievesub-second convergence for years

• Proper network design is a must

Design to use address summarization to limit query scope

Design to provide at least one feasible successor

• We can sort typical convergence times:

EIGRP with a feasible successor

Link state protocols

EIGRP without a feasible successor

• Cisco is currently in the process of quantifying scalability numbers

Configuring Bandwidth




RST-3221

11050_05_2005_X2

• EIGRP paces packets based on the configuredbandwidth

• Default bandwidth on serial linksis 1544 (T1)

• Just using the default isn’t always right





RST-3221

11050_05_2005_X2

• For point-to-point links (PPP, HDLC,ATM), configure the actual bandwidth

available on the link• For burstable links, configure

the normal bandwidth, not

the burst• For point-to-point subinterfaces

off a multipoint link, configurethe committed access rate, rather than the line speed





RST-3221

11050_05_2005_X2

• For 0 CIR links, guess

• You need to set it highenough to get EIGRP towork, so 56k is probablya reasonable number





RST-3221

11050_05_2005_X2

• If you need to changethe amount of actualbandwidth EIGRP is

using, use the percentagebandwidth interfacecommand to adjust this,rather than setting thebandwidth

• IP Percentage-Bandwidth EIGRP <AS><Percentage>

• By default, EIGRP uses 50% of the configuredor default bandwidth




1 512k il bl




RST-3221

11050_05_2005_X2

• 1 peer: 512k available

• 2 peers: 256k available



• 5 peers: 102k available• 3 peers: 170k available

• 4 peers: 128k available• 5 peers: 102k available

Remote Sites

A

512k


• At some point EIGRP won’t




RST-3221

11050_05_2005_X2

• At some point, EIGRP won thave enough bandwidth tooperate correctly

• Use dialer profiles for diallinks, which makesEIGRP treat them aspoint-to-point links.

• Use subinterfacesfor multipointinterfaces

Remote Sites

A

512k

Problems with Using Bandwidth

• Assume you would like to




RST-3221

11050_05_2005_X2

• Assume you would like toinfluence the path that packetsswitched by router A will take to

router D

• Using bandwidth, you will need tolower the bandwidth on the A-Clink or the A-B link to somethinglower than 56K

• Bandwidth is not granular enough to effectivelycontrol traffic flow

A

B C

D

56K 56K

1000K 1000K

Control over These

Two Links Only!


Reducing the bandwidth on




RST-3221

11050_05_2005_X2

• Reducing the bandwidth oneither the A-B or the A-C linkwill also impact EIGRP’soperation

• EIGRP uses the configuredbandwidth to control the rate atwhich packets are transmittedacross a link via the packetpacing timer

A

B C

D

56K 56K

1000K 1000K

Must be reduced

dramatically to

impact path

selection!


• Don’t use bandwidth to




RST-3221

11050_05_2005_X2

• Don t use bandwidth toinfluence path selection!

• Set the bandwidth to the

actual available bandwidth,and use the delay toinfluence traffic flow

• Delay is added inbound;

set the delay on A’s interfacewhich connects to B or C

A

B C

D

56K 56K

1000K 1000K

Configure

delay here

Multiple Autonomous Systems

Do You Really Want to Do This?




RST-3221

11050_05_2005_X2

Do You Really Want to Do This?

• Okay, maybe it’s not that bad…• But we still wouldn’t recommend it


AS 100• A route is redistributed from




RST-3221

11050_05_2005_X2

AS 100

AS 200

RIP

A B

C

A route is redistributed fromRIP into AS 200.

• At A, it is redistributed into AS

100.• B receives this route as well;

which of the two externals willit prefer?

• There are two routes learnedthrough separate routingprocesses with the sameadministrative distance, so theroute installed first wins.


AS 100• If router B prefers




RST-3221

11050_05_2005_X2

AS 100

AS 200

RIP

A B

m e

t r i c 1

0 0 0

C

m e t r i c 5 0 0

• If router B prefersthe route through AS 100, itwill redistribute the route

back into AS200.

• If the redistribution metric atB is lower than theredistribution metric at C, A

will prefer the path throughB.

• We have a permanent loop!


AS 100




RST-3221

11050_05_2005_X2

AS 200

RIP

A B

• External routescan also carry administrativetags; as the external route is

redistributed into AS 100 at A,it can be tagged.

• This tag can then be used toblock the redistribution of the

route back into AS 200 at B.

tag 100

route-map settag deny 10

match tag 100

route-map settag permit 20

!

router eigrp 200

redistribute eigrp 100 route-map settag


set tag 100

!

router eigrp 100


....


AS 100• This blocks the formation of




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AS 200

RIP

A B

• This blocks the formation of the loop, since A will no longer receive the redistributed from

B through AS 200.• B still receives both routes,

however, and could stillchoose the path through AS

100, resulting in suboptimalrouting.

tag 100


set tag 100

!

router eigrp 100


....

route-map filtertag deny 10

match tag 100

route-map filtertag permit 20

!

router eigrp 200

redistribute eigrp 100 route-map filtertag


• CSCdm47037 resolves the routing loop and the




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CSCdm47037 resolves the routing loop and thesuboptimal routing.

• If two routes with the same administrativedistances are compared, and the process type isthe same (both EIGRP), then compare the metricsof the routes as well.

• http://www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCdm47037


AS 100• If the redistribution metric is

http://www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCdm47037

http://www.cisco.com/cgi-bin/Support/Bugtool/onebug.pl?bugid=CSCdm47037




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AS 200

RIP

not manually set at A, it will becarried from AS 200 into 100.

• The cost of the path between Aand B is then added at B.

• At B, the route through AS 200wins; it has the lower metric.

A B

metric 1000

metric 1500

IP-EIGRP Topology Table for AS(100)/ID(10.0.17.10)

....P 10.1.1.0/24, 1 successors, FD is 1500

via 10.0.6.4 (1500/1000), FastEthernet0/0

....

IP-EIGRP Topology Table for AS(200)/ID(10.2.17.10)

....




• CSCdt43016, Support for Incoming Route Filtering




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CSCdt43016, Support for Incoming Route FilteringBased on Route Maps, makes it possible to filter routes based on any route map condition before itis accepted into the local routing protocoldatabase.

• This is listed as an OSPF feature, but it works for all routing protocols.

• http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122relnt/xprn122t/122tnewf.htm#33626


AS 100

Thi bl k th f ti f




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AS 200

RIP

A B

• This blocks the formation of the loop, since B will no

longer have the pathredistributed from A into AS100 in its topology table.

• This also prevents the

suboptimal routing.

tag 100


set tag 100

!

router eigrp 100


....

route-map settag deny 10

match tag 100


!

router eigrp 200

distribute-list settag filter in


• But, before you rush off




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yand configure your network with multiple

autonomous systems…• What are you gaining

by designing a networkthis way?


AS 100• A query originates at router




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AS 200

A B

C

q u e r

y

r e

p l y

C, and propagates to router A.

• The query stops at A, and areply is sent back.

• The query range has been

limited at A; the querystopped there, and wasreplied to. Or has it? ....


AS 100• What happens at A in AS 100?A now needs to query all of its




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AS 200

A B

C

q u e r

y

r e

p l y

A now needs to query all of itsneighbors, including theneighbors in AS 100.

• A builds a query in AS 100, andsends it to B. If the timing isright, B will have alreadyreceived and replied to thequery from C, so it wouldanswer that it has no alternatepath.

• The query wasn’t stopped, itwas just delayed along the

way!


AS 100• Don’t use multiple autonomoust f li th d ’t




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AS 200

A B

C

q u e r

y

r e

p l y

systems for scaling, they don’tlimit query range.

• General scaling methods(summarization, distribute lists,stubs, etc.) actually limit queryscope.

• Multiple autonomous systemsare fine for merging twonetworks over time, but theyare not a permanent solution



Managing EIGRP


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Managing EIGRP

• Reading the EIGRPT l T bl




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Topology Table

• Reading Show IP EIGRP

Neighbors

• Neighbor Logging

• Event Log

• MIB



Reading the EIGRP Topology Table

router#show ip eigrp topologyIP-EIGRP Topology Table for AS(1)/ID(70.1.1.2)

Codes: P - Passive A - Active U - Update Q - Query R - Feasible




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Codes: P - Passive, A - Active, U - Update, Q - Query, R -

Reply,

r - reply Status, s - sia Status

P 41.1.28.52/30, 1 successors, FD is 21026560via 60.1.1.2 (21026560/20514560), FastEthernet1/0


StateComputedDistance

Reported

Distance

FeasibleSuccessor

Successor

FeasibleDistance

Reading the EIGRP Topology Table

• Show ip eigrp topology activeInformation about links that are currently in active state




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Information about links that are currently in active state

• Show ip eigrp topology all-links

Displays all information about everything that EIGRP has inthe topology table

• Show ip eigrp topology <net> <mask>

Displays everything that the eigrp process has for aspecific route

• Show ip eigrp topology zero

Shows the “zero successor” links, or routes that don’tmake it into the routing table as another route with a better Admin Distance has won

Reading Show IP EIGRP Neighbors

• Handle: Internal use to keep track of the Neighbors• Address: Neighbor IP address• Interface: Local Interface which connects to that Neighbor




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• Hold Time: Seconds remaining before declaring that neighbor down• Uptime: The period of time since the neighbor was most recently discovered

• SRTT: The number of milliseconds it takes for this neighbor to respond toreliable packets• RTO: How long we’ll wait before retransmitting if we get no acknowledgement• Q Cnt: Number of outstanding packets waiting to be acknowledged by theneighbor

• Seq Num: Counter to track the number of packets sent to the neighbor

router#show ip eigrp neighbor

IP-EIGRP neighbors for process 1

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

4 1.1.1.5 Gi0/0.100 14 01:09:54 326 1956 0 417750148

0 1.1.1.6 Gi0/0.100 14 1d19h 63 378 0 91717867

412 120.0.14.126 Tu928 14 1d22h 1155 5000 0 105

404 120.0.11.210 Tu757 14 1d22h 988 5000 0 83

1003 120.0.5.106 Tu347 12 1d22h 51 5000 0 101

Neighbor Logging

• Provides the frequency and reason that a neighbor changesstate




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state

• Strong recommendation to always have this functionality

enabled

Enabled under router eigrp process

eigrp log-neighbor-changes

Default behavior since 12.2(12)

• Use the logging buffer to minimize potential impact

Enabled globally: logging buffered 10000

Neighbor Logging - Demystified!

• New Adjacency - Why look dear, we have a new neighbor.Either initial startup or recovery after a neighbor has gone down.

• Holding Time Expired – No EIGRP packets were seen from this neighbor for the




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Holding Time Expired No EIGRP packets were seen from this neighbor for theduration of the hold time.

Typically 15 seconds, though some are 180.

• Peer Restarted - Not my fault!

The other router reset the peer and that’s where you need to look to find the reason.

• Retry Limit Exceeded - A reliable packet was not acknowledged after at least 16retransmissions.

(Actual number is based on the hold time, but there were at least 16.)

• Route Filter Change - EIGRP doesn’t refresh routes. When a filter changes thataffects what is sent to the peers the neighbor is dropped to remove the old infoand then it is retold with the new filter in place. (Graceful Restart could minimizethe impact of this!)

Apr 21 11:02:22.285: … Neighbor 40.1.24.134 (ATM1/0.2934) is up: new adjacency

Apr 21 11:02:22.941: … Neighbor 40.1.16.98 (ATM1/0.1955) is down: holding time expired

Apr 21 11:02:22.953: … Neighbor 40.1.7.86 (ATM1/0.872) is down: peer restarted

Apr 21 10:52:24.787: … Neighbor 60.1.1.2 (FastEthernet1/1) is down: retry limit exceed

Apr 21 11:12:42.945: … Neighbor 40.1.16.110 (ATM1/0.1963) is down: route filter changed

Event Log

• The most important tool for getting a view of what’s going onin the network.




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• Always running, separate log kept per AS

• Default 500 lines (very little actually…)

eigrp event-log-size <number of lines>

0 lines disables logging

If you can spare the memory (very little) increasing the size isrecommended!

• Read from the bottom up as new events are written on top.

• The log may be cleared by entering:clear ip eigrp event

MIB Support

• Introduction of EIGRP MIB

12.3(14T)




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12.3(14T)

Included in images with SNMP feature base

• Currently IPv4 only, but IPv6 in the works

(along with EIGRP for IPv6, 12.4(T))

• Implemented Per AS, Per VPN basis

Allows for granular reporting and management of EIGRP in multi AS,VPN and non-VPN networks

• Sample configuration:

Router(config)# snmp-server host 10.0.0.1 traps version 2c NETMANAGER eigrp

Router(config) snmp-server community EIGRP1NET1A

Router(config)# snmp-server enable traps eigrp

MIB Support

• Includes two Traps

eigrpRouteSIA




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eigrpRouteSIA

eigrpAuthFailure

• 5 Object Groups on a per VPN, per AS basis

EIGRP VPN Table

EIGRP Traffic StatisticsEIGRP Topology Data

EIGRP Neighbor Data

EIGRP Interface Data

• For more specifics on the objects and MIB please see the following:http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00803d2d3d.html

MIB Support

• EIGRP Traffic StatisticsAS Number

• EIGRP Interface DataPeer Count

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00803d2d3d.html







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Hellos Sent/Received

Updates Sent/Received

Queries Sent/Received

Replies Sent/Received

• EIGRP Topology DataDestination Net/Mask

Active StateFeasible Successors

Origin Type

Distance

Reported Distance

Reliable/Unreliable Queues

Pacing

Pending Routes

Hello Interval

• EIGRP Neighbor DataPeer Address

Peer InterfaceHold Time

Up Time

SRTT/RTO

Version

AND MANY MORE...

Further Reading




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ASIN: 1578701651 ISBN: 0201657732 ISBN 1587051877

Complete Your Online Session Evaluation!

• Win fabulous prizes! Give us your feedback!

• Receive 10 Passport Points for each




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Receive 10 Passport Points for eachsession evaluation you fill out

• Go to the Internet stations locatedthroughout the Convention Center

• Winners will be posted on the Internetstations and digital plasma screens

• Drawings will be held in theWorld of Solutions

Monday, June 20 at 8:45 p.m.

Tuesday, June 21 at 8:15 p.m.Wednesday, June 22 at 8:15 p.m.

Thursday, June 23 at 1:30 p.m.




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eigrp deployment

Documents