Redistrute Connected vs (Routing) Network Statement

[jerry.marsh]

It appears from the following text in a Cisco manual

"Routes configured with the connected keyword affected by this redistribute command are the routes not specified by the network router configuration command."

That the REDISTRIBUTE CONNECTED statement is an alternative to specifiying the directly connected interfaces on a NETWORK statement of a routing protocol. And further that networks directly connected to a router with REDISTRIBUTE CONNECTED statement present do not need to be included in the NETWORK statements.

Is this a correct understanding?? Any other implications or gotchas of configuring it one way versus the other?

[Richard Burts]

Depending on what you need that may not be a correct understanding. There are several things that you should understand about comparing these configuration options. If you use the network statement then the routing protocol will run on that interface, will send and receive HELLO messages, will form neighbor relationships, will advertise its routes to neighbors on that interface. If you use redistribute connected then the routing protocol will advertise the subnet of the interface on its active interfaces but will not run on the interface, will not send and receive HELLO messages, will not form neighbor relationships and will not send and receive routing updates on that interface.

So if your requirements are only to advertise the subnet of the interface but not necessarily to send and receive routing updates on the interface then redistribute connected will work fine for you. Otherwise you should use the network statement.

Another implication that you should understand is that if you use redistribute connected then the route that is generated will be treated as an external route. If you use the network statement then the route that is generated will be treated as an internal route. It may make some difference in your network whether the route is internal or external.

HTH

Rick

[jerry.marsh]

Are saying that with REDISTRIBTE CONNECTED only (without a NETWORK statement) that though routes may be sent and heard, there is not EIGRP "peering". I'm not clear about what you said.

[Kevin Dorrell]

With redistribute connected (without network), there will be no peering through that network. No routes will be sent or heard either. The only route that will appear in the routing protocol would be that of connected network itself - and not anything heard indirectly through it.

Furthermore, if your routing protocol distinguishes between internal and external routes, the redistubuted routes will be flagged as external. For example, in EIGRP other routers will see it with an administrative distance of 170, as opposed to a route generated by "network" which would have an AD of 90. (Of course, locally within the originating router, the connected route would win with an AD of 0.)

Hope this helps.

Kevin Dorrell

Luxembourg