ppp and ripv2

Answered Question
Aug 19th, 2009

Hi every body.

Let say we have a network

R1s0-----------------s0R2f0-----

I intentionally used two different subnet on so on both routers.

R1

int s0

10.10.10.1/24

encapsulation ppp

clockrate 56000

R2

int s0

ip address 10.10.11.1/24

encapsulation ppp

int fo

ip address 12.12.12.12/24

==============================

Ping on R1 to R2's0 will be successful.

Let say we enabled ripv2 on both routers. Will R2 be able to exchange routes on s0 with R1 as so int on both are in different subnet?

I am just wondering because ospf or eigrp won't exchange routes in the above case. But how about ripv2?

Thanks.

I have this problem too.
0 votes
Correct Answer by Lucien Avramov about 7 years 3 months ago

correct, doesnt that remind you when you studied for ccie. it reminds me on the lab days. How to disable the route, turn off the neighbor-route.

Correct Answer by Edison Ortiz about 7 years 3 months ago

That's the 'peer neighbor-route' knob that is enabled by default on PPP interfaces.

Correct Answer by Jon Marshall about 7 years 3 months ago

Lucien

I don't think it's the book, rather this is the way Sarah learns ie. by reading the core stuff and then coming up with unusual scenarios to make sure she fully understands it.

And it keeps us all on out toes as well to be honest :-)

Jon

Correct Answer by Lucien Avramov about 7 years 3 months ago

To add, to that if you advertise other networks, you will observe what ediortiz said:

Before the command no validate-update-source:

*Aug 20 00:19:42.178: RIP: ignored v2 update from bad source 10.10.10.1 on Serial

AfteR:

IP: received v2 update from 10.10.10.1 on Serial0/0/0:0

And then the route gets installed, so yes it will work

Correct Answer by Lucien Avramov about 7 years 3 months ago

actually the routing table will show it as directly connected anyway:

Gateway of last resort is not set

2.0.0.0/30 is subnetted, 1 subnets

C 2.2.2.0 is directly connected, FastEthernet0/1

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.10.11.1/32 is directly connected, Serial0/0/0:0

C 10.10.10.0/24 is directly connected, Serial0/0/0:0

So rip is not even in use in the ppp scenario between r1 and r2

Correct Answer by Edison Ortiz about 7 years 3 months ago

It's not a bad design scenario when you are forced to preserve IP addressing space and rely on 'ip unnumbered' on WAN interfaces.

Correct Answer by Edison Ortiz about 7 years 3 months ago

With RIP you can actually accept routes without verifying the source IP but you have to turn off 'validate-update-source' which is enabled by default

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_rip.html#wp1012874

HTH,

__

Edison.

Correct Answer by Jon Marshall about 7 years 3 months ago

Sarah

No they can't exchange routes. Even though they do not form neighborships in the way EIGRP/OSPF do they still reject the routing update with the following message -

RIP: ignored V2 update from bad source - 10.10.10.1 on s0/0

the above was seen on R2 from your example.

Jon

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Correct Answer
Jon Marshall Wed, 08/19/2009 - 15:54

Sarah

No they can't exchange routes. Even though they do not form neighborships in the way EIGRP/OSPF do they still reject the routing update with the following message -

RIP: ignored V2 update from bad source - 10.10.10.1 on s0/0

the above was seen on R2 from your example.

Jon

Lucien Avramov Wed, 08/19/2009 - 15:55

wondering why a book would keep on turning to you BAD design scenarios, not a good way to learn proper configs.

Actually this will work, look at the next posts for the debug outputs from my lab.

Correct Answer
Edison Ortiz Wed, 08/19/2009 - 16:01

It's not a bad design scenario when you are forced to preserve IP addressing space and rely on 'ip unnumbered' on WAN interfaces.

Correct Answer
Jon Marshall Wed, 08/19/2009 - 16:11

Lucien

I don't think it's the book, rather this is the way Sarah learns ie. by reading the core stuff and then coming up with unusual scenarios to make sure she fully understands it.

And it keeps us all on out toes as well to be honest :-)

Jon

sarahr202 Wed, 08/19/2009 - 18:00

Thanks Jon and all of you.

Thanks to you guys and my stupid scenarios, i have learned a lot which i could not have learned by just reading books.

thanks all of you, see you again with more stupid questions :-)

Correct Answer
Lucien Avramov Wed, 08/19/2009 - 16:04

actually the routing table will show it as directly connected anyway:

Gateway of last resort is not set

2.0.0.0/30 is subnetted, 1 subnets

C 2.2.2.0 is directly connected, FastEthernet0/1

10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 10.10.11.1/32 is directly connected, Serial0/0/0:0

C 10.10.10.0/24 is directly connected, Serial0/0/0:0

So rip is not even in use in the ppp scenario between r1 and r2

Correct Answer
Lucien Avramov Wed, 08/19/2009 - 16:08

To add, to that if you advertise other networks, you will observe what ediortiz said:

Before the command no validate-update-source:

*Aug 20 00:19:42.178: RIP: ignored v2 update from bad source 10.10.10.1 on Serial

AfteR:

IP: received v2 update from 10.10.10.1 on Serial0/0/0:0

And then the route gets installed, so yes it will work

Correct Answer
Edison Ortiz Wed, 08/19/2009 - 16:15

That's the 'peer neighbor-route' knob that is enabled by default on PPP interfaces.

Correct Answer
Lucien Avramov Wed, 08/19/2009 - 16:16

correct, doesnt that remind you when you studied for ccie. it reminds me on the lab days. How to disable the route, turn off the neighbor-route.

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