Discontiguous networks and auto summarization?

Llukman1

Hello everyone,

It would be wonderful if someone can clear this up for me as best as they can.
So in the environment where you have Discontiguous Networks, RIP is not going to work until you prevent RIP manually from Auto Summarization.
My question is why does it summarize over discontiguous networks only?

clarson

computers are designed to do just what you tell them to do. you configure them to do what you want them to do. You don't know how to configure them, they probably aren't going to do what you think they should do.

you turn on the rip routing protocol. you turn on auto summarization because it is the default. things will work just fine if the discontiguous portion of your network doesn't exist. But, you have laid the groundwork for future problems when that discontiguous network portion gets added. And, if the discontiguous portion exists some where else in your network, you have just created a routing problem.

So, if you have discontiguous networks, you configure rip with no auto summarization. no problems now, no problems later.

My question is why does it summarize over discontiguous networks only?
rip does auto sumarrization over networks, weather they are discontiguous or not. you have continuous networks, auto summary is a good thing.

So in the environment where you have Discontiguous Networks, RIP is not going to work until you prevent RIP manually from Auto Summarization.
No, rip is going to work. it is going to work just how you configured it. It just isn't going to work like you want it to work.

what you need to know is how routing protocols work and how a router does it routing.
if there is a single network configured in the routing protocol, how are the packets going to be routed
if there are many networks configured in the routing protocol, how are the packets going to be routed for the know networks
if the many networks are summarized into one network, how are the packets going to be routed.
now if the summarized network is discontiguous, how are the packets going to be routed.
your routing protocol is going to be advertising to the other routers that it knows where to send packets for the discontiguous portion of the network. it is going to be telling the routers to send the packets to a place that doesn't exist. is that a problem?

leonlimsg

Fyi, auto-summary is enabled by default for EIGRP and RIPv2. You have to manually disable auto-summary.