ccna v3.0 semester 3 ccna v3.0 module 1 introduction to classless routing

CCNA v3.0 Semester 3

CCNA v3.0Module 1

Introduction to Classless Routing

CCNA v3.0 Semester 3 2

What is VLSM?

A Variable Length Subnet Mask (VLSM) is a means of allocating IP addressing resources to subnets according to their individual need rather than some general network-wide rule.

VLSM allows an organization to use more than one subnet mask within the same network address space. It is often referred to as ‘subnetting a subnet’, and can be used to maximize addressing efficiency.

Large subnets are created for addressing LANs and small subnets are created for WAN links (a 30 bit mask is used to create subnets with only two host).


Subnetting vs. VLSM

• Subnetting allows you to divide big networks into smaller, equal-sized slices.

• VLSM allows you to divide big networks into smaller, different-sized slices. This enables you to make maximum use of your valuable IP address space.

• So basically, you are now utilizing subnet masks in the same IP address space.


Routing Protocols Supporting VLSM

• RIP v2

• EIGRP

• OSPF


Addressing a Network with Standard Subnetting

• Site A has two Ethernet networks• Site B had one Ethernet network• Site C had one Ethernet network

207.21.24.0 /24

How many network addresses are needed?

How many hosts are needed for the largest LAN?

How many bits need to be borrowed to address this network?

Site A Site B Site C

25 users 25 users 10 users 8 users



• Site A has two Ethernet networks• Site B had one Ethernet network• Site C had one Ethernet network



If we borrow 3 bits from a class C address, that will give us eight networks, but we can only use six of them. Each network will have 30 usable addresses.

It will take four network addresses to accommodate the Ethernet networks at each site. That leaves us with two extra networks.

There is also a point-to-point WAN connection between each site. These two connections will take up the remaining two networks.



Borrowing 3 bits will meet the current needs of the company, but it leaves little room for growth.

Each network will have 30 usable addresses, including the point-to-point WAN links (which only require two addresses).



Subnet # Subnet AddressBits Masked

0 207.21.24.0 /271 207.21.24.32 /272 207.21.24.64 /273 207.21.24.96 /274 207.21.24.128 /275 207.21.24.160 /276 207.21.24.192 /277 207.21.24.224 /27

207.21.24.0


We can use subnet 0To enable subnet 0 on a Cisco router (if not already

enabled), it is necessary to use the global configuration

command ip subnet-zero.

Router# configure terminal (config t)

Router(config)# ip subnet-zero

To disable subnet 0, use the no form of this command.

Router(config)# no ip subnet-zero


Subnetting in a Box

0

255

In a class C network there are 256 addresses.

Provides 1 network with 256 addresses.

When we subnet the address, we break it down in to smaller units or subnets.

Subnet mask: 255.255.255.0

256 addresses


Subnetting in a Box

0

255

128

127

Borrowing 1 bit would break the 256 addresses in to two parts (networks)

Providing 2 networks each with 128 addresses.

Subnet mask: 255.255.255.128.

128 addresses 128 addresses


Subnetting in a Box

0

255

128

127

64

63

Borrowing 2 bits would break each of the 2 networks in half again.

Providing 4 networks, each with 64 addresses.

Subnet mask: 255.255.255.192.

64 addresses

64 addresses

64 addresses

64 addresses

192

191


Subnetting in a Box

0

255

128

127

64 192

63 191

Borrowing 3 bits would break each of these 4 networks in half again.


Subnet mask: 255.255.255.224.

32addresses

32addresses

31

32

32addresses

32addresses

95

96

32addresses

32addresses

159

160

32addresses

32addresses

223

224


Subnetting in a Box

0

255

128

127

64 192

63 191

Borrowing 4 bits would break each of these 8 networks in half again.


Subnet mask: 255.255.255.240.

31

32

95

96

159

160

223

224

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16addresses

16

15

48

47

144

143

176

175

80

79

112

111

208

207

240

239


Addressing a Network Using VLSM

• When using VLSM to subnet an address, not all of the subnets have to be the same size.

• A different subnet mask may be applied to some of the subnets to further subnet the address.

• In order to take advantage of VLSM, the proper routing protocol must be selected.

• Not all routing protocols share subnetting information in their routing table updates.

Classful Routing Protocols(do not share subnet info)

Classless Routing Protocols(do share subnet info)

RIP v1 RIP v2IGRP EIGRP

OSPFIS-IS



To subnet using VLSM, identify the LAN with the largest number of hosts. Subnet the address 207.21.24.0 /24 based on this information.

• Site A has two Ethernet networks (25 hosts each)• Site B had one Ethernet network (10 hosts)• Site C had one Ethernet network (8 hosts)



Subnet # Subnet AddressBits Masked

0 207.21.24.0 /271 207.21.24.32 /272 207.21.24.64 /273 207.21.24.96 /274 207.21.24.128 /275 207.21.24.160 /276 207.21.24.192 /277 207.21.24.224 /27



Subnet 1 & 2 to address Site A Ethernet networks.

Subnet 5 to accommodate Site B & C Ethernet networks.

Subnet 6 can be subnetted to accommodate the WAN links.Site A Site B Site C


Free Addresses

Site A

Subnet # Subnet Address

0 207.21.24.0 /271 207.21.24.32 /272 207.21.24.64 /273 207.21.24.96 /274 207.21.24.128 /275 207.21.24.160 /276 207.21.24.192 /277 207.21.24.224 /27

Site B & C

Sub-subnet 0 207.21.24.160 /28Sub-subnet 1 207.21.24.176 /28

Site BSite C


0 207.21.24.0 /271 207.21.24.32 /272 207.21.24.64 /273 207.21.24.96 /274 207.21.24.128 /275 207.21.24.160 /276 207.21.24.192 /277 207.21.24.224 /27

WAN links

Sub-subnet 0 207.21.24.192 /30Sub-subnet 1 207.21.24.196 /30Sub-subnet 2 207.21.24.200 /30Sub-subnet 3 207.21.24.204 /30Sub-subnet 4 207.21.24.208 /30Sub-subnet 5 207.21.24.212 /30Sub-subnet 6 207.21.24.216 /30Sub-subnet 7 207.21.24.220 /30

Free Addresses

WAN 1 & 2


0 207.21.24.0 /271 207.21.24.32 /272 207.21.24.64 /273 207.21.24.96 /274 207.21.24.128 /275 207.21.24.160 /276 207.21.24.192 /277 207.21.24.224 /27



Through applying VLSM, the topology was able to be addressed and still have two complete subnets available for future growth.



207.21.24.32 /27 207.21.24.64 /27 207.21.24.160 /28

207.21.24.176 /28

207.21.24.192 /30

207.21.24.196 /30


Addressing a Network Using VLSMExercise 1

Your company IP network is 195.39.71.0 /24. Headquarters is connected to five branch offices by a WAN link, and to an ISP. Determine an appropriate IP addressing scheme. (the ISP owns the addresses on its link)

Headquarters

Branch 1

60 users

12 users 12 users 12 users 12 users 12 usersBranch 2 Branch 3 Branch 4 Branch 5

ISP


195.39.71.0 /24

Subnet according to the largest subnet needed. (Headquarters 60 hosts)

0

255

128

127

64 192

63 191

Borrow 2 bits or /26. This would give you 4 networks with 64 host addresses on each subnet.


Playing it safe, we will not use the first subnet (subnet 0).

0

64

128

192We will start addressing with 195.39.71.64 /26.

Headquarters needs 60 hosts, so we will assign them .64 - .127.

Headquarters

60 hosts

26 bit mask or /26

(255.255.255.192)


The 5 Branch offices need 12 hosts each.

0

64

128

192

The next address block available is the .128 - .191 block. Use VLSM.

Headquarters

60 hosts

26 bit mask or /26

(255.255.255.192)

Using a /28 mask will give us 16 hosts at each location. This will take care of 4 of the Branch offices.

160

144 176

Branch 112 hosts

/28(255.255.255.240)

Branch 212 hosts

/28(255.255.255.240)

Branch 312 hosts

/28(255.255.255.240)

Branch 412 hosts

/28(255.255.255.240)


To obtain a block for Branch 5, we will need to subnet the .192 - .255 block using a /28 mask.

0

64

128

192

Headquarters

60 hosts

26 bit mask or /26

(255.255.255.192)

160

144 176

Branch 112 hosts

/28(255.255.255.240)

Branch 212 hosts

/28(255.255.255.240)

Branch 312 hosts

/28(255.255.255.240)

Branch 412 hosts

/28(255.255.255.240)

224

208

Branch 512 hosts

/28(255.255.255.240)


Now connect the 5 WAN links to the Branch offices.

These are point-to-point connections and only require 2 addresses.

0

64

128

192

Here we will use a /30 mask to further subnet the subnets.

Headquarters

60 hosts

26 bit mask or /26

(255.255.255.192)

160

144 176

Branch 112 hosts

/28(255.255.255.240)

Branch 212 hosts

/28(255.255.255.240)

Branch 312 hosts

/28(255.255.255.240)

Branch 412 hosts

/28(255.255.255.240)

224

208

Branch 512 hosts

/28(255.255.255.240)

232

228 236

WAN 1

WAN 2

WAN 3

WAN 4

248

244

WAN 5

240


Any remaining networks could be used for future growth of either LANs or WANs.

Subnet 0 could also be further subnetted according to the needs of the network.

0

64

128

192

Headquarters

60 hosts

26 bit mask or /26

(255.255.255.192)

160

144 176

Branch 112 hosts

/28(255.255.255.240)

Branch 212 hosts

/28(255.255.255.240)

Branch 312 hosts

/28(255.255.255.240)

Branch 412 hosts

/28(255.255.255.240)

224

208

Branch 512 hosts

/28(255.255.255.240)

232

228 236

WAN 1

WAN 2

WAN 3

WAN 4

248

244

WAN 5

240


Address provided by ISP195.39.71.64 /26

195.39.71.128 /28 195.39.71.144 /28 195.39.71.160 /28 195.39.71.176 /28 195.39.71.192 /28

195.39.71.208 /3019

5.39

.71.

212

/30

195.

39.7

1.21

6 /3

0

195.39.71.220 /30

195.39.71.224 /30

Applying the Addresses to the Topology


Classful AddressingThe IPv4 address architecture uses (a/n)

8 bit network number for Class A addresses

16 bit network number for Class B addresses

24 bit network number for Class C addresses

1 - 126

128 - 191

192 - 223

Class B

Network Host

1 0

Class C

Network Host

1 1 0

Class A

Network Host

0


Classful Addressing

Classful addressing (A, B, C…) is obsolete.

Address Class

ApplicationNumber of

Network BitsNumber of Host Bits

Decimal Address Range

Number of Addresses

Number of Possible Host

Class ALarge

Networks8 bits 24 bits 1 - 126 126 16,777,214

Class BMedium-sized

Networks16 bits 16 bits 128 - 191 65,534 65,534

Class C Small Networks 24 bits 8 bits 192 - 223 2,097,152 254

The Class System


Classless Interdomain RoutingCIDR (pronounced “cider”) ignores class.

Using CIDR, a router views a bit mask to determine the network and host portions of an address.

This allows CIDR to craft network address spaces according to the size of a network instead of force-fitting networks into pre-sized network address spaces.


Classless Interdomain RoutingCIDR sounds a lot like VLSM

CIDR is usually discussed in general Internet context (ISPs)– Uses custom length prefixes to reduce workload in

key Internet routers

VLSM is usually discussed in enterprise context– Uses custom length prefixes to have better usage

of enterprise address space


Classless Interdomain RoutingRouters use the network-prefix, rather than the first 3

bits of the IP address, to determine the dividing point between the network number and the host number.

In the CIDR model, each piece of routing information is advertised with a bit mask or prefix-length ( /x ). The prefix-length is a way of specifying the number bits in the network-portion of each routing table entry.


Classless Interdomain RoutingFor example, a network with 20 bits of network-number

and 12 bits of host-number would be advertised with a 20 bit prefix (/20).

The clever thing is that the IP address advertised with the /20 prefix could be a former Class A, Class B, or Class C.

All addresses with a /20 prefix represent the same amount of address space (212 or 4,096 host addresses).

20 bits network + 12 bits host


Classless Interdomain RoutingAddress space can now be assigned in “chunks” that fit

the need.

If an organization needs 254 host addresses, what difference does it make whether they are given:– a Class C (200.23.76.0 /24)

– 1/256th of a Class B (145.38.20.0 /24)

– 1/65,536th of a Class A (91.187.7.0 /24)

Using a /24 prefix, each of these specifies eight host bits which will support 254 hosts.


Network Prefix Equivalent Number of Class Addresses Number of Hosts

/27 1/8th of a Class C 32

/26 1/4th of a Class C 64

/25 1/2 of a Class C 128

/24 1 Class C or 1 /24 256

/23 2 Class C or 2 /24s 512

/22 4 Class C or 4 /24s 1,024

/21 8 Class C or 8 /24s 2,048

/20 16 Class C or 16 /24s 4,096

/19 32 Class C or 32 /24s 8,192

/18 64 Class C or 64 /24s 16,384

/17 128 Class C or 128 /24s 32,768

/16 256 Class C or 1 Class B 65,536

/15 512 Class C or 2 Class B 131,072

/14 1,024 Class C or 4 Class B 262,144

/13 2048 Class C or 8 Class B 524,288

/12 4096 Class C or 16 Class B 1,048,576

/11 8192 Class C or 32 Class B 2,097,152

/10 16384 Class C or 64 Class B 4,194,304

/9 32768 Class C or 128 Class B 8,388,608

/8 65,536 Class C or 256 Class B or 1 Class A 16,777,216

Prefix Equivalents


Route Aggregation w/ CIDR or (Summarization)

You need 500 addresses.

Given two consecutive /24 addresses:

(200.201.202.0 /24 and 200.201.203.0 /24)

This address space could be advertised to the rest of the Internet as 200.201.202.0 /23.

Why? (the two /24s have the first 23 bits in common). 11001000.11001001.11001010.00000000

11001000.11001001.11001011.00000000

23 bits network prefix


CIDR Scenario continued

If the ISP owns all of the 200.201.0.0 networks (256 /24s), why should it advertise all of them separately?

Instead, it could simply advertise 200.201.0.0 /16 (which would be 200.201.0.0 /24 through 200.201.255.0 /24).

This would reduce the size of the routing tables on the router to which the routes are advertised.

11001000.11001001.00000000.00000000

11001000.11001001.11111111.00000000

16 bits network prefix

.0.0

.255.0


CIDR Scenario continued

The summary of route 200.201.202.0 /23 is called a “CIDR block” or a supernet.

Because we are dealing with binary, the block size is always a power of two (2, 4, 8, 16, 32, etc.). The starting point of the block must be a multiple of the power of two that is being used (21 … 2, 4, 6, 8, etc.).

– 200.201.202.0

– 200.201.204.0

– 200.201.206.0

– 200.201.208.0

– 200.201.210.0

Examples of starting addresses


Network Prefixes200.201.200.0 11001000.11001001.11001000.00000000

200.201.201.0 11001000.11001001.11001001.00000000

200.201.202.0 11001000.11001001.11001010.00000000

200.201.203.0 11001000.11001001.11001011.00000000

200.201.204.0 11001000.11001001.11001100.00000000

200.201.205.0 11001000.11001001.11001101.00000000

200.201.206.0 11001000.11001001.11001110.00000000

200.201.207.0 11001000.11001001.11001111.00000000

200.201.208.0 11001000.11001001.11010000.00000000

200.201.209.0 11001000.11001001.11010001.00000000

200.201.210.0 11001000.11001001.11010010.00000000

200.201.211.0 11001000.11001001.11010011.00000000

23 bits

200.201.200.0/23

200.201.202.0/23

200.201.204.0/23

200.201.206.0/23

200.201.208.0/23

200.201.210.0/23



200.201.201.0 11001000.11001001.11001001.00000000

200.201.202.0 11001000.11001001.11001010.00000000

200.201.203.0 11001000.11001001.11001011.00000000

200.201.204.0 11001000.11001001.11001100.00000000

200.201.205.0 11001000.11001001.11001101.00000000

200.201.206.0 11001000.11001001.11001110.00000000

200.201.207.0 11001000.11001001.11001111.00000000

200.201.208.0 11001000.11001001.11010000.00000000

200.201.209.0 11001000.11001001.11010001.00000000

200.201.210.0 11001000.11001001.11010010.00000000

200.201.211.0 11001000.11001001.11010011.00000000

22 bits

200.201.204.0/22

200.201.200.0/22

200.201.208.0/22



200.201.201.0 11001000.11001001.11001001.00000000

200.201.202.0 11001000.11001001.11001010.00000000

200.201.203.0 11001000.11001001.11001011.00000000

200.201.204.0 11001000.11001001.11001100.00000000

200.201.205.0 11001000.11001001.11001101.00000000

200.201.206.0 11001000.11001001.11001110.00000000

200.201.207.0 11001000.11001001.11001111.00000000

200.201.208.0 11001000.11001001.11010000.00000000

200.201.209.0 11001000.11001001.11010001.00000000

200.201.210.0 11001000.11001001.11010010.00000000

200.201.211.0 11001000.11001001.11010011.00000000

21 bits

200.201.200.0/21


CIDR in a NutshellHand out pieces of classful networks (to avoid wasting

addresses)

Identify the network portion of an address with a network prefix ( /x)

Advertise blocks of networks (to reduce the size of routing tables).


CIDR Example

Objective

Create an addressing scheme using VLSM.

Scenario

You are assigned the CIDR address 200.32.108.0 /22 and you must support the network shown in the diagram. Create an addressing scheme that will meet the diagram requirements.

300 users 100 users 100 users

100 users


Dissect the problemGiven the CIDR address 200.32.108.0 /22

How many /24 networks do we have?

How many host addresses do we have?

What is the largest LAN requirement?


100 users


Address given - 200.32.108.0 /22

Host required - 300, 100, 100, 100, and 3 WAN links

200.32.108.0 200.32. 110.0

0 0

0 0255 255

255 255

200.32. 109.0 200.32. 111.0


Address given - 200.32.108.0 /22

Host required - 300, 100, 100, 100, and 3 WAN links0 0

0 0255 255

255 255

300

hos

ts

200

.32.

108

.0 /2

3

200.32.108.0 200.32. 110.0

200.32. 109.0 200.32. 111.0


Address given - 200.32.108.0 /22


0 0255 255

255 255

300

hos

ts

200

.32.

108

.0 /2

3127

128

100

hos

ts

200

.32.

110

.0 /2

5

100

hos

ts

200

.32.

110

.128

/25

200.32.108.0 200.32. 110.0

200.32. 109.0 200.32. 111.0


Address given - 200.32.108.0 /22


0 0255 255

255 255

300

hos

ts

200

.32.

108

.0 /2

3127

128

100

hos

ts

200

.32.

110

.0 /2

5

100

hos

ts

200

.32.

110

.128

/25

127

128

100

hos

ts

200

.32.

111

.0 /2

5

200.32.108.0 200.32. 110.0

200.32. 109.0 200.32. 111.0


Address given - 200.32.108.0 /22


0 0255 255

255 255

300

hos

ts

200

.32.

108

.0 /2

3127

128

100

hos

ts

200

.32.

110

.0 /2

5

100

hos

ts

200

.32.

110

.128

/25

127

128

100

hos

ts

200

.32.

111

.0 /2

5

191192

223

224

248

247

243252

251244

WAN links /30

240239

200.32.108.0 200.32. 110.0

200.32. 109.0 200.32. 111.0


CIDR ResultGiven the CIDR address 200.32.108.0 /22


100 users

200.32.108.0 /23 200.32.110.0 /25 200.32.110.128 /25

200.32.111.0 /2520

0.32

.111

.240

/30 200.32.111.248 /30

200.

32.1

11.2

44 /

30

Two /24s


Classless Interdomain RoutingFor the router to operate in a classless manner and match destination IP addresses to a CIDR network address,

The global command: ip classless must be configured.

Router(config)# ip classless


Routing Information Protocol(RIP)

•RIP is a relatively old, but still commonly used interior gateway protocol (IGP).

•It was created for use in small homogeneous networks.

•It is a distance-vector protocol that is used with classful IP addressing only.

•RIP v1 sends routing update messages at regular intervals (30 seconds) and when the network topology changes.

•RIP uses hop count as its only metric and maintains only the best route to a destination.


RIP Version 2

•Known as RIP V2

In RIP v2 all of the operation procedures, timers, and

stability functions of RIP v1 remain the same in version

2, with the exception of the broadcast updates.

RIP v2 has become the standard version of RIP used

in networks today.


RIP V2 is RIP V1 with extensions

• Subnet masks carried with each route entry

• Authentication of routing updates

• Next-hop addresses carried with each route entry

• External route tags

• Multicast route updates


RIP v2

The most important of these extensions is the addition

of a Subnet Mask field

This enables the use of variable-length subnet masks

(VLSMs) and qualifies RIP v2 as a classless routing

protocol.RIP v2 Packet Format

RIP v1 Packet Format


RIP v2

• RIP v2 allocated a 4-octet field to associate a subnet

mask to a destination IP address.

• When used in tandem, the IP address and its subnet

mask enable RIP v2 to specifically identify the type of

destination that the route leads to.

• This allows RIP v2 to route specific subnets,

regardless of whether the subnet mask is fixed or of

variable length.

RIP v2 Packet Format


RIP v2

RIP v2 differs from RIP v1 in the way update aresent out.

• RIP v1 sends updates as a broadcast (all stations

receive the broadcast message)

• RIP v1 does not send subnet mask information in

its updates.

• RIP v2 sends updates as a multi-cast. Multi-casting

is a technique for simultaneously advertising routing

information to multiple RIP devices via the class D

address 224.0.0.9


RIP v1 & RIP v2 comparisons

• Both use hop count as a metric

• Both have the same metric value for infinite distance (16)

• Both use split horizon to prevent routing loops.

• RIP v1 broadcasts routing table updates, while RIP v2 multicasts its updates


Configuring RIP v1

To configure RIP v1 on a router, enter the following commands:

Router# config tRouter(config)# router ripRouter(config-router)# network 192.168.12.0

NOTE - If no version is specified in the configuration, version

1 will be used. The router will listen for version 1 and 2

updates but send only version 1.


Configuring RIP v2

To take advantage of version 2s features, it is necessary to turn off version 1 support and enable version 2 updates with the following commands:

Router(config)# router ripRouter(config-router)# version 2

Router(config-router)# network 192.168.12.0

NOTE - The default behavior can be restored by entering the

command no version in the config-router mode.

Router(config)# router ripRouter(config-router)# no version


Verifying & Troubleshooting RIP

• show ip route to make sure routers have learned all networks dynamically

• show ip protocols to see information about the routing protocols used.

• debug ip RIP to see live routing updates


You can override the default behavior of RIP by configuring a particular interface to behave differently.

Overriding Default Behavior of RIP

Interface e0 sends and receives version 1 updates only.

RIP v2 configured on the router.

Router(config)# router ripRouter(config-router)# version 2Router(config-router)# network 192.168.12.0Router(config-router)# exit

Router(config)# int e0Router(config-if)# ip address 192.168.12.33 255.255.255.224Router(config-if)# ip rip send version 1Router(config-if)# ip rip receive version 1


You can override the default behavior of RIP by configuring a particular interface to behave differently.

Interface e2 has no special configuration and therefore sends and receives version 2 by default.

Overriding Default Behavior of RIP

Interface e1 sends and receives both version 1 and 2 updates.

Router(config)# int e1Router(config-if)# ip address 192.168.12.65 255.255.255.224 Router(config-if)# ip rip send version 1 2 Router(config-if)# ip rip receive version 1 2

Router(config)# int e2Router(config-if)# ip address 192.168.12.97 255.255.255.224


Review of Static & Default Routing


Configuring static routes w/ outgoing interface

Administrative distance of 0 - default

outgoing interface


Configuring static routes w/ next-hop IP address

Administrative distance of 1 - default

Next hop interface


Configuring Static RoutesRemember, an administrator actually enters these routes into the

routing table.That makes them static route entries – because the router is not

“discovering” those routes.If for some reason that outgoing interface goes down or is not

available for some reason, then at that time the route will be removed from the routing table.

Show ip route shows the routing table.The route would still be in the configuration (because it was entered

globally), but that route could now no longer be used by the router because the interface it refers to is down for some reason.


Administrative Distance

What is the default for a outgoing interface?What is the default for the next-hop address?Defaults can always be changed!!!Just make it higher if you want it to be a

“backup” route.

ip route 192.168.2.0 255.255.255.0 192.188.4.1 120


Router A Router B Router C

S0 192.168.2.1/24

S1 192.168.2.2/24

S0 192.168.4.1/24

S1 192.168.4.2/24

192.168.1.0/24 192.168.3.0/24 192.168.5.0/24

What would you enter to configure a static route from Router C to the LAN on Router A using outgoing interface?

The LAN on Router B from Router A using next-hop?


The static default route

A router should be configured with a special type of static route – a default route.

This default route routes packets with destinations that do not match any of the other routes in the routing table

It is a “gateway of last resort” that allows the router to forward “destination unknown” packets out a particular interface

ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoing interface]


Default Route on non-directly connected networks

CCNA v3.0 Semester 3

CCNA v3.0Module 1

Introduction to Classless Routing

ccna v3.0 semester 3 ccna v3.0 module 1 introduction to classless routing

Documents

network addresses

ethernet network site

ccna v3

addresses slide

standard subnetting

class c network

network address space

site bsite c