01-21-2010 06:35 AM - edited 03-04-2019 07:15 AM
Hi,
We have three routers R0--> R1-->R2 connected by serial point to point link.
On all Eigrp is running and working properly. When we summazie routes on R0 on ser 1/0
ip summary-route eigrp 1 10.10.0.0 255.255.0.0. This route is advertised to R1 and R2 but admin distance
shown is 90. I was wondering if that should be 5 as that route is eigrp summary route.
From R2 I am able to ping 10.10.1.1 which is interface on R0. That means summarization is working.
Please share the experience.
Thanks in advance.
Subodh
Solved! Go to Solution.
01-21-2010 07:00 AM
Hello Subodh,
you should find a static route to nullo with AD 5 on router where you have configured the ip eigrp summary route.
It is important to remember that EIGRP creates this static route to nullo with AD 5, because it can create problems.
suppose you want to send out only a default route. Without adding a final parameter like 200 that will be the AD of the static route to null0 the risk is that default route of local node is overriden by the static to null0 creating a black hole.
neighbors will classify the route as EIGRP internal route, so you cannot see AD 5 on them.
what you see is normal
see
ip summary-address eigrp as-number ip-address mask [admin-distance] [leak-map name]
http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_i1.html#wp1019434
Hope to help
Giuseppe
01-21-2010 07:45 AM
Subdoh
Just to add to Giuseppe's post.
The summary route is AD 5 on the local router only. And as Giuseppe said the next-hop of that route on the local router is always null0. The reason for it being lower than any internal/external EIGRP is to prevent routing loops. So traffic that matches the summary address will be sent to this router. If this router does not have a more specific route for the destination then you want that traffic to be dropped, hence the reason the AD is set to 5 so it takes priority over any internal or external EIGRP routes.
Jon
01-21-2010 07:00 AM
Hello Subodh,
you should find a static route to nullo with AD 5 on router where you have configured the ip eigrp summary route.
It is important to remember that EIGRP creates this static route to nullo with AD 5, because it can create problems.
suppose you want to send out only a default route. Without adding a final parameter like 200 that will be the AD of the static route to null0 the risk is that default route of local node is overriden by the static to null0 creating a black hole.
neighbors will classify the route as EIGRP internal route, so you cannot see AD 5 on them.
what you see is normal
see
ip summary-address eigrp as-number ip-address mask [admin-distance] [leak-map name]
http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_i1.html#wp1019434
Hope to help
Giuseppe
01-22-2010 05:30 AM
Hi,
Thanks a lot, cleared one more "concept" !!
Thanks
Subodh
01-21-2010 07:45 AM
Subdoh
Just to add to Giuseppe's post.
The summary route is AD 5 on the local router only. And as Giuseppe said the next-hop of that route on the local router is always null0. The reason for it being lower than any internal/external EIGRP is to prevent routing loops. So traffic that matches the summary address will be sent to this router. If this router does not have a more specific route for the destination then you want that traffic to be dropped, hence the reason the AD is set to 5 so it takes priority over any internal or external EIGRP routes.
Jon
01-22-2010 05:28 AM
Hi,
Thanks a Lot Jon.Marshal.
Subodh
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