Question about EIGRP summary-address advertisements
I have a router running EIGRP, with a summary address configured on one interface, using the "ip summary-address eigrp" command. This creates a route to null0 in the local routing table, for that summary address, like this:
D 10.10.0.0/16 is a summary, 3d21h, Null0
The summary works the way I want it to, and all's good so far, but...
I'll be adding a new EIGRP neighbor for this router to peer with. My requirement is that the new neighbor receive the advertisements from this router for the *specific* routes in that summary network, but *cannot* receive the summary advertisement itself. The new neighbor will not be hanging off the interface with the summary address configured; it will be on a different interface.
My questions are these:
1) In a default configuration (with no special filtering set up), would the new neighbor receive an EIGRP advertisement for the summary route? I would guess that it would, since it appears in the table of the existing router as an EIGRP route.
2) If the answer to the first question is yes, how can I filter the summary route from the outbound advertisements, while still allowing all the smaller routes from that network through? A prefix-list would be ideal for this (and is how I handle the issue when redistributing between protocols)--but as far as I can tell, I can't apply a prefix-list to simple advertisements between routers speaking the same protocol. If I use a distribute-list with a regular ACL, I'm not sure how I can prevent the summary route, say 10.10.0.0/16, but still allow, for instance, the smaller network 10.10.0.0/24 to be advertised.
Re: Question about EIGRP summary-address advertisements
Well, I may have just answered my own question... When I first asked the question, I was foolishly reading the documentation on options for filtering outbound advertisements, and the doc (configuration guide for 12.4T) only showed the option of using an ACL with the distribute-list. However, I just went into my router and did a "distribute-list ?" under EIGRP configuration just to see whether any additional options showed up, and it looks like I can use a prefix-list after all:
<1-199> IP access list number
<1300-2699> IP expanded access list number
WORD Access-list name
gateway Filtering incoming updates based on gateway
prefix Filter prefixes in routing updates
route-map Filter prefixes based on the route-map
So... never mind. Guess I'll stop reading the documentation from now on!
(I'm still curious about whether the router will try to advertise the summary to the new neighbor, but I guess as long as I can block it with a prefix-list it doesn't really matter.)
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