うらねこ

This is very basic atomic primitive important issue but I note it intentionally for my understanding.

When you use mutual redistribution between IGPs, you need to care for connected networks.

Assuming IGP-A and IGP-B are redistributed mutually:

• If a connected network is included IGP-A, the connected route is redistributed into IGP-B, in spite of the route is not shown Router’s  ip route table as IGP-B (since it should be shown as connected, naturally.)
• If a connected route is NOT included IGP-A, the route is not redistributed into IGP-B. You need to say “redistribute connected” if you want to redistribute it.

This is very simple, but sometime it might make you confused. At least I’m confused occasionally…

Additional information:

If you will say “redistribute connected”, above rules are not applied. For example, when you set “redistribute connected route-map INTERFACES”, only the interfaces permitted in the route-map are redistributed even if other connected interfaces are included in source IGP.