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New Member

Routing Question

I am working in Netsim, and have 4 routers. I am trying to get RIP working.

Router 1= corp router = s0/0 10.1.1.1, s0/1 10.1.2.1, s0/2 10.1.3.1

Router 2= branch router s0/0 10.1.1.2, e1/0 10.1.5.1, e1/1 10.1.6.1

Router 3= branch router s0/0 10.1.2.2, e1/0 10.1.7.1, e1/1 10.1.8.1

Router 4= branch router s0/0 10.1.3.2

I used the following commands on all routers:

rip router

network 10.0.0.0

When I do a sh ip route...no rip routes.

Below are two excerpts:

Corp router:

interface Serial0/0

ip address 10.1.1.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

interface Serial0/1

ip address 10.1.2.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

router rip

network 10.0.0.0

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 4 subnets

C 10.1.1.0 is directly connected, Serial0/0

C 10.1.4.0 is directly connected, Serial0/3

C 10.1.2.0 is directly connected, Serial0/1

C 10.1.3.0 is directly connected, Serial0/2

Branch router1:

interface Serial0/0

ip address 10.1.1.2 255.255.255.0

no ip directed-broadcast

!

!

interface Ethernet1/0

ip address 10.1.5.1 255.255.255.0

no ip directed-broadcast

!

interface Ethernet1/1

ip address 10.1.6.1 255.255.255.0

no ip directed-broadcast

router rip

network 10.0.0.0

10.0.0.0/24 is subnetted, 4 subnets

C 10.1.5.0 is directly connected, Ethernet1/0

C 10.1.6.0 is directly connected, Ethernet1/1

C 10.1.1.0 is directly connected, Serial0/0

C 10.1.4.0 is directly connected, Serial0/1

  • WAN Routing and Switching
13 REPLIES
Hall of Fame Super Bronze

Re: Routing Question

You are experiencing the split-horizon rule.

All the subnets you mentioned are the same in their classful nature so the router won't accept advertisement it already knows about.

If you can fix this problem by going with version 2 under RIP and enable no auto-summary

__

Edison.

Re: Routing Question

You need to configure "version 2" in router configuration mode.

RIP version 1 doesn't support variable-length subnet masking. The RIP process on each of your routers is therefore only reporting network 10.0.0.0. Since each router already has this network, with a)longer masks/prefixes and b)lower administrative distance (directly connected vs RIP); they won't place any of RIP's info into their routing tables.

Set each one up for RIPv2 and you should be in better shape.

(please remember to rate helpful posts)

Hall of Fame Super Silver

Re: Routing Question

Edison

I do not see how you analyze this as a split horizon issue. In the original post it is pretty clear that the Branch router is connected via its serial to the Corp router. And the Branch router has 2 subnets on its Ethernet interfaces that match the RIP network statement. So how does split horizon prevent the Branch from advertising its Ethernet subnets over the serial interface?

Seth

How do you analyze this as a variable length subnet issue. In the original post it is pretty clear that all subnets are 255.255.255.0. All are the same length and not variable.

I am not clear what the problem is, but I do not believe that it is either split horizon or VLSM.

I would like to see a more complete configuration of these router to try to identify what the issue is. I would also like to see the output of show cdp neighbor detail to verify that the routers are connected as the original post suggests that they are. And the output of show ip protocol would also be helpful.

HTH

Rick

Re: Routing Question

Hmmm, yes I suppose they are all 24-bit masks. I shoulda looked more closely at the configs.

But you are right, we need more info on the configs as well as on the layer 2 state of things.

New Member

Re: Routing Question

Ok guys, here is the config from the Corp router and one of the branch routers. You are correct there is two subnets off the branch router (10.1.5.0/24, 10.1.6.0/24).

Please note this is in Netsim.

************************

Corp router

**********************

corprouter#sh run

Building configuration...

!

Version 12.1

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname corprouter

!

!

!

!

ip subnet-zero

!

!

!

!

!

!

!

!

!

interface Serial0/0

ip address 10.1.1.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

interface Serial0/1

ip address 10.1.2.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

interface Serial0/2

ip address 10.1.3.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

interface Serial0/3

ip address 10.1.4.1 255.255.255.0

no ip directed-broadcast

clock rate 64000

!

interface Ethernet1/0

no ip address

no ip directed-broadcast

shutdown

!

interface Ethernet1/1

no ip address

no ip directed-broadcast

shutdown

!

interface Ethernet1/2

no ip address

no ip directed-broadcast

shutdown

!

interface Ethernet1/3

no ip address

no ip directed-broadcast

shutdown

!

!

router rip

network 10.0.0.0

!

!

!

ip classless

no ip http server

!

!

!

!

!

line con 0

transport input none

line aux 0

line vty 0 4

!

no scheduler allocate

end

*********************

BRANCH ROUTER

*********************

Router#SH RUN

Building configuration...

!

Version 12.1

service timestamps debug uptime

service timestamps log uptime

no service password-encryption

!

hostname Router

!

!

!

!

ip subnet-zero

!

!

!

!

!

!

!

!

!

interface Serial0/0

ip address 10.1.1.2 255.255.255.0

no ip directed-broadcast

!

interface Serial0/1

ip address 10.1.4.2 255.255.255.0

no ip directed-broadcast

!

interface Serial0/2

no ip address

no ip directed-broadcast

shutdown

!

interface Serial0/3

no ip address

no ip directed-broadcast

shutdown

!

interface Ethernet1/0

ip address 10.1.5.1 255.255.255.0

no ip directed-broadcast

!

interface Ethernet1/1

ip address 10.1.6.1 255.255.255.0

no ip directed-broadcast

!

interface Ethernet1/2

no ip address

no ip directed-broadcast

shutdown

!

interface Ethernet1/3

no ip address

no ip directed-broadcast

shutdown

!

!

router rip

network 10.0.0.0

!

!

!

ip classless

no ip http server

!

!

!

!

!

line con 0

transport input none

line aux 0

line vty 0 4

!

no scheduler allocate

end

________________________________

From the Corp router I can ping:

10.1.1.2

From the branch router I can ping:

10.1.1.1

10.1.5.1

10.1.6.1

10.1.5.11 (one of the PC's)

________________________

******************

CORP ROUTER

******************

corprouter#SH IP ROUTE

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 4 subnets

C 10.1.1.0 is directly connected, Serial0/0

C 10.1.4.0 is directly connected, Serial0/3

C 10.1.2.0 is directly connected, Serial0/1

C 10.1.3.0 is directly connected, Serial0/2

**********************

BRANCH ROUTER

**********************

Router#sh ip route

Gateway of last resort is not set

10.0.0.0/24 is subnetted, 4 subnets

C 10.1.5.0 is directly connected, Ethernet1/0

C 10.1.6.0 is directly connected, Ethernet1/1

C 10.1.1.0 is directly connected, Serial0/0

C 10.1.4.0 is directly connected, Serial0/1

Re: Routing Question

But from the corp router you can't ping 10.1.2.1 or 10.1.3.1?

So far you've only verified layer 2 connectivity to Router 2. What about the other branch routers?

Can you give us the output of "show ip rip database" on the corp router?

New Member

Re: Routing Question

Yes. I can ping all the branch routers from the corp router.

I cannot however ping any networks connected via the branch routers.

"sh ip rip database" is not available in netsim.

If I add a static route to 10.1.5.1 on the corp router. They are able to ping each other.

Hall of Fame Super Silver

Re: Routing Question

The configs as posted look ok and I would expect RIP to be advertising the subnets. If the route tables are not showing that I wonder if there is some aspect of netsim that we are encountering. Perhaps the output of show ip interface brief and the output of show ip protocol might shed some light on this.

HTH

Rick

New Member

Re: Routing Question

Here is the output. - Thanks for your help.

**************

Corp Router

**************

Interface IP-Address OK? Method Status Protocol

Serial0/0 10.1.1.1 YES unset up up

Serial0/1 10.1.2.1 YES unset up up

Serial0/2 10.1.3.1 YES unset up up

Serial0/3 10.1.4.1 YES unset up up

Ethernet1/0 unassigned YES unset administratively down down

Ethernet1/1 unassigned YES unset administratively down down

Ethernet1/2 unassigned YES unset administratively down down

Ethernet1/3 unassigned YES unset administratively down down

Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 28 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Outgoing update filter list for all interfaces is

Incoming update filter list for all interfaces is

Redistributing: rip

Default version control: send version 1, receive any version

Interface Send Recv Key-chain

Serial0/0 1 1 2

Serial0/1 1 1 2

Serial0/2 1 1 2

Serial0/3 1 1 2

Routing for Networks:

10.0.0.0

Routing Information Sources:

10.1.2.2 120 00:00:03

10.1.1.2 120 00:00:015

Distance: (default is 120)

***************

Branch Router

***************

Router#sh ip int brief

Interface IP-Address OK? Method Status Protocol

Serial0/0 10.1.2.2 YES unset up up

Serial0/1 unassigned YES unset administratively down down

Serial0/2 unassigned YES unset administratively down down

Serial0/3 unassigned YES unset administratively down down

Ethernet1/0 10.1.7.1 YES unset up up

Ethernet1/1 10.1.8.1 YES unset up up

Ethernet1/2 unassigned YES unset administratively down down

Ethernet1/3 unassigned YES unset administratively down down

Router#sh ip protocol

Routing Protocol is "rip"

Sending updates every 30 seconds, next due in 29 seconds

Invalid after 180 seconds, hold down 180, flushed after 240

Outgoing update filter list for all interfaces is

Incoming update filter list for all interfaces is

Redistributing: rip

Default version control: send version 1, receive any version

Interface Send Recv Key-chain

Serial0/0 1 1 2

Ethernet1/0 1 1 2

Ethernet1/1 1 1 2

Routing for Networks:

10.0.0.0

Routing Information Sources:

10.1.2.1 120 00:00:06

Distance: (default is 120)

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