Single router two connection

[debnath.subrata872]

On a single router if we have connected two different networks with different process IDs configured will they communicate or not.if yes, what needs to be done to communicate with each other?

[Kasun Bandara]

@debnath.subrata872 hi, normally is same router have 2 connections connected directedly it will allow communication between those 2 networks unless we configure ACL to filter traffic. what you mean by process ID? 

[Richard Burts]

I agree with KB that assuming that ip routing is enabled (which is the default on Cisco routers) that 2 networks connected to the router would be able to communicate with each other without any additional configuration.

And agree that the reference to process ID is not clear. Can you give us more detail about this environment?

[Joseph W. Doherty]

By default, the router with two different routing processes will form one route table, containing the information from both, which means the router can route between those two topologies.  However, the router will not share, with other routers, the combined route topologies.

For example, if you had R1<OSPF>R2<EIGRP>R3 (or R1<OSPF10>R2<OSPF20>R3), R2 "knows" about both the OSPF and EIGRP topologies and will route between them (by default).  However, R1 will not "know" about EIGRP routes and conversely R3 will not "know" about OSPF routes.

If you want a router to pass routes between different routing processes, you do that via "redistribution" (which there's much to understand, as different routing protocols use different metrics, you may want to selectively only share some routes, and/or you need to deal with precluding "looping" redistributed routes).