Discontiguous Network ?

[rivanfrank]

Hi,

In connection to my last post, I somehow read about the discontiguous network. When I saw the network I made, I think it is a discontiguous network. I thought RIP won't work but I can ping each others host.

Here is my network configured by RIP.

Can someone enlighten me about discontiguous network? And in my case why did RIP is still sending/receiving route updates?

Thanks.

[Abzal · Accepted solution]

Hi,

If you are running RIPv1:

1. In your network regardless of auto-summary option both routers will advertise 192.168.16.0/192.168.8.0 with /24 mask as it is class C network. Because RIPv1 do not advertise with prefixes.

2. There could be a problem if on both sides e.g. subnets 192.168.8.0/25 and 192.168.8.128/25. When router receives update it check whether it has an interface on this subnet. If it has already then it ignores the update. Because these subnets advertised with /24 mask.

RIPv2:

1. version 2, advertise subnets with prefixes. If an update did cross major network boundary with auto-summary option it will summarize subnets. If did not then regardless of auto summary it won't summarize.

Hope it will help.

Best regards,
Abzal

[Jan Hrnko · Accepted solution]

Hi,

In connection to my last post, I somehow read about the discontiguous network. When I saw the network I made, I think it is a discontiguous network. I thought RIP won't work but I can ping each others host.

Just to make everything clear, yes, the network you have made is indeed a discontiguous network.

But as Abzal have said, it WILL work in any case (RIPv1,RIPv2) because 192.168.x.x are class C networks and as a class C networks - they are expected to have mask of /24.

Best regards,

Jan

[rivanfrank]

Thank You!

I understand that RIP will summarize the network to /24 because it is a class c address, I was more concerned in the 10.0.0.0 network and then I realized it will not affect both 192.168.8.0 and 192.168.16.0 network right? Since it is only like a bridge on both network (not a bridge device function). Am i correct?

Thanks.

[Abzal · Accepted solution]

Yes, it's correct.

Imagine you have a subnet 10.1.1.0/24 on 10.0.0.2 router.

With RIPv2 there shouldn't be a problem. Because it would arvertise this subnet with a prefix (/24). And 10.0.0.1 router would add it to RIB(routing table).

But with RIPv1 it wouldn't see this subnet because second router would advertise subnet without a prefix, just 10.0.0.0/8. So router would not accept it and to RIB as it has already subnet on interface.

Hope it will help.

Best regards,
Abzal