CIDR is compatible with RIPv1? I think not ... Why RIPv1supernets learning?

I have a question .... if you have 2 routers directly connected. The first configured with RIPv1.The second configured with RIPv2.
The router configured with RIPv2 redistribute a static route 172.16.0.0/12, as it is possible that the router configured with RIPv1 learn this route? I've checked with Packet Tracer and GNS3 ... Someone can explain me.Thank you.
Raul.

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Comments

ehnde

172.16.0.0/12 is a classful route, that is why RIPv1 can understand it. If you break down that /12 to, say, a /23 - then your RIPv1 router will still see it as 172.16.0.0/12.

saspro

172.16.0.0 is a class B address. Shouldn't that be a /16?

ehnde

saspro wrote: »

172.16.0.0 is a class B address. Shouldn't that be a /16?

Yes, you're right. I got my bit boundaries bass ackwards. Sorry hadn't had enough coffee yet.

saspro

ehnde wrote: »

Yes, you're right. I got my bit boundaries bass ackwards. Sorry hadn't had enough coffee yet.

It's afternoon over here so I'm wired on coffee by now (whilst running through practice exams at work)

hilbert69

ehnde wrote: »

172.16.0.0/12 is a classful route, that is why RIPv1 can understand it. If you break down that /12 to, say, a /23 - then your RIPv1 router will still see it as 172.16.0.0/12.

I do not agree with that 172.16.0.0/12 is a classfull route,Notice that the /12 mask (255.240.0.0) is less than the default classful mask /16 (255.255.0.0).Classfull routes have /8,/16 or /24.The route 172.16.0.0/12 is the summarization of the following networks:from 172.16.0.0/16 to 172.31.0.0/16.Conclusions:172.16.0.0/12 is a "supernet".Thank you.
Raul.

saspro

hilbert69 wrote: »

I do not agree with that 172.16.0.0/12 is a classfull route,Notice that the /12 mask (255.240.0.0) is less than the default classful mask /16 (255.255.0.0).Classfull routes have /8,/16 or /24.The route 172.16.0.0/12 is the summarization of the following networks:from 172.16.0.0/16 to 172.31.0.0/16.Conclusions:172.16.0.0/12 is a "supernet".Thank you.
Raul.

Maybe I do need more coffee as well (or to finish up reading about some of this).

Doesn't redistribution "translate" to other protocols? This would mean the v2 router would send it to the v1 router in a format the v1 router understands.

What does the routing table on Router 1 show?

hilbert69

This is the resultat:
R2#sh ip route
1.0.0.0/30 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
R 172.16.0.0/12 [120/1] via 1.1.1.1, 00:00:26, FastEthernet0/0

MrRyte

hilbert69 wrote: »

This is the resultat:
R2#sh ip route
1.0.0.0/30 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, FastEthernet0/0
R 172.16.0.0/12 [120/1] via 1.1.1.1, 00:00:26, FastEthernet0/0

If RIPv1 is the routing protocol then shouldn't that be /16?

Excellent1

ehnde wrote: »

Yes, you're right. I got my bit boundaries bass ackwards. Sorry hadn't had enough coffee yet.

From reading some of the replies in this thread, I get the feeling you won't be living this one down for a while...

Just giving you a hard time, man. It's all in good fun.

hilbert69

MrRyte wrote: »

If RIPv1 is the routing protocol then shouldn't that be /16?

I think so too. But I have tried in the Packet Tracer and GNS3 and achieving the same result. It's very strange assuming that RIPv1 does not support CIDR.

MrRyte

hilbert69 wrote: »

I think so too. But I have tried in the Packet Tracer and GNS3 and achieving the same result. It's very strange assuming that RIPv1 does not support CIDR.

According to this link:
Cisco IOS IP and IP Routing Command Reference, Release 12.1 - RIP Commands [Cisco IOS Software Releases 12.1 Mainline] - Cisco Systems

Command

Description

ip rip receive version

Specifies a RIP version to receive on an interface basis.

ip rip send version

Specifies a RIP version to send on an interface basis.

show ip protocols

Displays the parameters and current state of the active routing protocol process.

It's possible to have a router send/receive two different RIP versions.
Can you post us the "show protocols" from the RIPv1 configured router?