eigrp characteristics · 2015-01-29 · configuring eigrp to prevent ... router eigrp as-no....

EIGRP Characteristics

Fast Convergence

Partial Updates

Protocol Module Dependence (PDM)

Use of multicast and unicast

Reliable Transport Protocol (RTP)

Diffusing Update Algorithm (DUAL)

Classless

Auto-Summary

EIGRP Steps to Add Route

Neighbor Discovery:

Send Hello Message and check parameters

Topology Exchange:

Full topology updates when become neighbor

Choosing Routes:

Select the lowest-metric route for each destination

EIGRP Terms Successor – Current Route

A successor is a route selected as the primary route to use to reach a destination.

Successors are the entries kept in the routing table.

Feasible Successor - A backup route A feasible successor is a backup route. These routes are selected at the same time the

successors are identified, but they are kept in the topology table.

Multiple feasible successors for a destination can be retained in the topology table.

EIGRP Terms Feasible distance (FD) - This is the lowest calculated metric

to reach destination. This is the route that you will find in the routing table (the best path)

Reported distance (RD) - The distance reported by an adjacent neighbor to a specific destination.

Interface information - The interface through which the destination can be reached.

Route status - Routes are either passive, which means that the route is stable and ready for use, or active, which means that the route is in the process of being recomputed by DUAL

EIGRP Packets and Metrics Hello

Update

Query

Reply

Acknowledge

Metric Calculation: Bandwidth, Delay, Reliability, Load

EIGRP Neighbors To establish neighbor relationship: Primary IP address in same subnet

Same AS

Same k-metric values

Neighbor Table Contents

Neighbor Discovery

1)A sends hello

2)B replies with update to A with initial bit set

3)Now adjacency established, A relies with Ack.

4)A inserts the information in its topology table

5)A sends update to B

6)B sends Ack to A

Diffusing Update Algorithm “DUAL” All route computations in EIGRP are handled by DUAL

One of DUAL's tasks is maintaining a table of loop-free paths to every destination.

This table is referred to as the topology table

DUAL saves all paths in the topology table

The least-cost path(s) is copied from the topology table to the routing table

In the event of a failure, the topology table allows for very quick convergence if another loop-free path is available

If a loop-free path is not found in the topology table, a route re-computation must occur

DUAL queries its neighbors, who, in turn, may query their neighbors, and so on...

Dual Process Feasible Distance (FD)

Advertise Distance (AD)

Successor

Feasible Successor (FS)

When no FS in router D:

1) Set metric for net A as unreachable (-1)

2) Change to Active state

3) Send queries to C and E

4) Mark C & E with query pending (q)

Dual Process At RouterD:

1- Dual receive reply from C that no change occur.

2- Remove “q” flag from C

3- Stay active for net A from E

At RouterC:

no change in successor

At E:

1- Dual queries C

2- Mark C as “q”

3- receive reply from C, remove “q”

4- calculate new FD and new successor

5- change from active to passive

6- E sends reply to D

EIGRP Configuration and verification

router eigrp as-no.

network network-no. [wildcard]

show ip route

show ip route eigrp

show ip protocols

show ip eigrp {neighbors|interfaces|topology|traffic}

debug eigrp {neighbors|packets}

debug ip eigrp [summary]

Configuring EIGRP

To prevent neighbor relationship over interface router eigrp as-no.

passive-interface {type no.} [default]

Propagate default route

ip default network network-no.

Manual Route Summary

router eigrp as-no.

no auto-summary

interface type no. ip summary-address eigrp as-no addr. mask [AD]

Configuring EIGRP

Create Authentications Key Chain:

key chain name

key number

key-string value

Enable EIGRP MD5 Authentication on an Interface

ip authentication mode eigrp as-no. md5

Use correct Key Chain to be used on an Interface

ip authentication key-chain eigrp as-no. chain-name

Route Status Passive (P): This network is available, indicating that no EIGRP computations

are being performed for this route.

Active (A): This network is currently unavailable, and installation cannot occur in the routing table and queries exist for this network,

Update (U): an update packet is being sent. The router is waiting for an acknowledgment for this update packet

Query (Q): indicating that a query packet was sent. This also applies if the router is waiting for an acknowledgment for a query packet.

Reply (R): The router is generating a reply for this network, indicating that a reply packet was sent, or is waiting for an acknowledgment for reply packet.

Reply status (r): Indicates the flag that is set after a query has been sent and is waiting for a reply.

Stuck-in-active (s): There is an EIGRP convergence problem for this network.

Stuck-in-Active (SIA) Queries might propagate through the network causing

expanding tree of queries If no reply received within 3 min, router goes to SIA state

timers active-time [time-limit |Disabled] When no response router reset the relationship with the

neighbor SIA-Query, SIA-Reply Limit query range: Summarization, stub routers

Stuck-in-Active (SIA)

Configuring EIGRP Stub Router To configure EIGRP stub feature:

eigrp stub [receive-only | connected | static | summary |redistributed]

receive-only keyword restricts the router from sharing its routes with any other router within an EIGRP AS

connected keyword permits the EIGRP stub routing feature to send connected routes

static keyword permits the EIGRP stub routing feature to send static routes

summary keyword permits the EIGRP stub routing feature to send summary routes

redistribute option permits the EIGRP stub routing feature to send redistributed routes

Graceful Shutdown

Router not need to wait its hold timer to expire in order to discover the change and select the feasible successor instead of missed successor

With graceful shutdown a goodbye message is broadcast when EIGRP process is shutdown

Implemented with the goodbye message feature

Designed to improve EIGRP network convergence

Graceful shutdown use the hello packet with all k values set to 255

EIGRP on Frame Relay “Dynamic Mapping”

interface Serial0/0

encapsulation frame-relay

ip address 192.168.1.101 255.255.255.0

router eigrp 110

network 172.16.1.0 0.0.0.255

network 192.168.1.0

EIGRP on Frame Relay “Dynamic Mapping”

Split-horizon is enabled by default on physical interface

EIGRP on Frame Relay “Static Mapping”

R1#show run

interface Serial0/0


ip address 192.168.1.101 255.255.255.0

frame-relay map ip 192.168.1.101 101

frame-relay map ip 192.168.1.102 102 broadcast

frame-relay map ip 192.168.1.103

router eigrp 110

network 172.16.1.0 0.0.0.255

network 192.168.1.0103 broadcast

R3#show run

interface Serial0/0


ip address 192.168.1.103 255.255.255.0


broadcast

router eigrp 110

network 192.168.1.0

EIGRP over FR Multipoint Subinterfaces

R3#show run

<output omitted>

interface Serial0/0

no ip address


interface Serial0/0.1 multipoint

ip address 192.168.1.103 255.255.255.0


broadcast

router eigrp 110

network 192.168.1.0

R1#show run

interface Serial0/0

no ip address


interface Serial0/0.1 multipoint

ip address 192.168.1.101 255.255.255.0

no ip split-horizon eigrp 110



broadcast


broadcast

router eigrp 110

network 172.16.1.0 0.0.0.255

network 192.168.1.0

EIGRP on FR Multipoint Subinterfaces

R1#show ip eigrp neighbors

IP-EIGRP neighbors for process 110

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

0 192.168.1.102 Se0/0.1 10 00:06:41 10 2280 0 5

1 192.168.1.103 Se0/0.1 10 00:08:52 10 2320 0 9

R3#show ip eigrp neighbors

IP-EIGRP neighbors for process 110

H Address Interface Hold Uptime SRTT RTO Q Seq

(sec) (ms) Cnt Num

0 192.168.1.101 Se0/0.1 10 00:10:37 10 1910 0 6

EIGRP Unicast Neighbors

Static configuration of EIGRP neighbors instead of dynamic neighbor discovery

Define neighbor to exchange unicast routing information instead of multicast

router eigrp as-no.

neighbor {ip-address | ipv6-address} interface-type interface-number

When configured on an interface no multicast is processed and no dynamic neighbor discovery

R1#show run

interface Serial0/0

no ip address


interface Serial0/0.2 point-to-point

ip address 192.168.2.101

255.255.255.0

frame-relay interface-dlci 102


ip address 192.168.3.101

255.255.255.0


router eigrp 110

network 172.16.1.0 0.0.0.255

network 192.168.2.0

network 192.168.3.0

R3#show run

interface Serial0/0

no ip address



ip address 192.168.3.103 255.255.255.0


router eigrp 110

network 172.16.3.0 0.0.0.255

network 192.168.3.0

EIGRP on FR Point-to-Point Subinterfaces

EIGRP Link Utilization EIGRP uses %50 of the bandwidth declared on an

interface or sub-interface

Percentage can be adjusted for an interface ip bandwidth-percent eigrp as-number percentage

For multipoint FR, EIGRP uses bandwidth of the interface divided by the number of neighbors

You should allocate suitable bandwidth to represent the minimum CIR times the number of circuits

EIGRP over MPLS

What is MPLS!!

IETF standard combines the advantages of layer 3 routing with layer 2 switching

Short fixed-length labels assigned to each packet at the edge of regular network

MPLS nodes examine the labels to forward the packets instead of IP header

MPLS handle IP services like VPN, end-to-end QoS to efficient utilization of existing network

MPLS connection-oriented technology

MPLS Terminology Label: short, fixed-length, physically contiguous identifier used to

identify a group of networks sharing a common destination.

Label stack: An ordered set of labels attached to a packet header. Each label in the stack is independent of the others.

Label swap: The basic forwarding operation, which consists of looking up an incoming label to determine the outgoing label, encapsulation, port, and other data-handling information.

Label-switched hop (LSH): The hop between two MPLS nodes, on which forwarding is done using labels.

Label-switched path (LSP): The path through one or more LSRs at one level of the hierarchy followed by a packet in a particular FEC.

Label switching router (LSR): An MPLS node that is capable of forwarding labeled packets.

MPLS Terminology

MPLS domain: A contiguous set of nodes performing MPLS routing and forwarding. These are typically in one routing or admin. domain.

MPLS edge node: An MPLS node that connects to a neighboring node outside of its MPLS domain.

MPLS egress node: An MPLS edge node that handles traffic leaving an MPLS domain.

MPLS ingress node: An MPLS edge node that handles traffic entering an MPLS domain.

MPLS label: A label carried in a packet header and represents the packet’s FEC.

MPLS node: operates one or more Layer 3 routing protocols, and capable of forwarding packets based on labels.

MPLS Terminology

Forwarding Equivalence Class (FEC): Grouping of possible packets into classes that are forwarded in the same manner.

Tag Distribution Protocol (TDP): Cisco propriety protocol

Label Distribution Protocol (LDP): Standard protocol

Resource Reservation Protocol (RSVP): Used by MPLS to allow on-demand reservation of bandwidth through MPLS network.

Label Forwarding Information Base (LFIB): stores label information for use of forwarding engine. It is built by information from LDB, BGP, RSVP.

VPN MPLS

L2 MPLS VPN

R1 and R2 on the same IP subnet

L3 MPLS VPN

R1 and R2 connected to ISP routers with separate IP subnets

MPLS Routers VRF separate routing process for

each customer at PE

PE participate in customer routing

Internal MPLS backbone (P-routers) are transparent to customer

MPLS Operation

Layer 3 header contains more than is necessary needed for forwarding the packets.

Penultimate hop pop

MPLS Operation

Label Allocation on Frame Mode

Each LSR locally assign label to each network existed in the routing table and stored in Label Information Base (LIB)

LSR announces its assigned label to its peers, who propagate the information to their peers.

The information received is stored on Forwarding Information Label (FIB) and Label Forwarding Information Label (LFIB)

LIB is part of control plane

LFIB is part of data plane

eigrp characteristics · 2015-01-29 · configuring eigrp to prevent ... router eigrp as-no....

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