Route tagging and summary statement question

Unanswered Question
Mar 26th, 2010

Scenerio: I need to use route tagging to control mutual route redistribution between Ripv2 and EIGRP on a 6500 Sup 720 running 12.2(33)SXI3. At the same time I would also like to summerize the routes on the interface between the two AS's (ie the RIPv2 interface).  RIPv2 is used to conect to another location running non-Cisco gear that I have little control over. In the attached diagram I have control over the devices at site 1, site 2 and site 3.

I can use a route-map as part of the EIGRP->RIPv2 redistribution to set all the tags but my question is what happens to those tags when I summerize the routres at the interface? In this scenerio MOST of the routes within a summary range will share the same tag but that is not neccessarily always true.

Summerizing is not 100% neccessary so if it causes more problems then its worth I can leave it out.  I have included a sanatized diagram of the network to help show whats going on.

I will comment that there are a host of other requirements embedded in this diagram so its a little hairy and the notes are psuedo-code that would be translated into route-map match and set conditions in the real configs.

Thanks for looking

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Sr. Network Communication Analyst
Lockheed Martin

I have this problem too.
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Giuseppe Larosa Fri, 03/26/2010 - 06:19

Hello Nathan,

to keep control over routes you should have the appropriate route tags associated to IP prefixes.

A summary route is less specific and used only if no more specific route (regardless of AD value) for the destination address exists.

your best choice may be that of avoiding summarization.

But your design should be able to deal with summary routes if EIGRP AS 2 is confined on that part of your network (bottom right corner)

You should deploy two redistribution points for redundancy at each border between different routing protocol domains.

You can also send a simple default route from ASBR nodes into EIGRP AS 2 domain.

Be also aware that RIPv2 tags are 16 bits unsigned integers instead of 32 bit unsigned integer like it happens for EIGRP and OSPF.

you can match on EIGRP route but then you need to set it explicitly in order to see the route-tag in RIPv2 for this reason.

Hope to help


Nathan Spitzer Fri, 03/26/2010 - 07:35

A summary route is less specific  and used only if no more specific route (regardless of AD value) for the  destination address exists.>

Yeah. The whole purpose of this is to get away from controlling the routes manually. The current method used is UGLY with 2 30+line access lists on each end (ingress and egress). Adding a new range on either end requires going through a whole change control process and sometimes still gets messed up so we want something automatic.

Its not nearly that simple (unfortunately). EIGRP2 has a default gateway that is not shown. The RIP link is only for routes in the OSPF area and a subset of routes in EIGRP 1.

Don't I know it. Made it much more difficult to come up with consistent meaningful tags. The OSPF guys HAD to pick a big long IP-type address for their OSPF area .

I have a feeling I may jetisone summerization and get over myself.

Tharak Abraham Fri, 03/26/2010 - 07:08

Neat diagram there sir..

Not sure whether itl help you but still some thoughts:-

1.Creating a static summary route with intended prefixes to null 0, match it with an access list and use the route-map to match the ACL and set the tag and redistribute

2.Enable auto-summary in eigrp, do the ACL and route-map matching and then redistribute with route tags.

3. Configuring eigrp LEAK-MAPS with incomplete references, not sure about this though but if you set a route map without references by just setting the might work (not sure though)

Nathan Spitzer Fri, 03/26/2010 - 07:39

Good ideas but the whole goal is something automatic so new ranges automagically get routed right. Auto-summary is not an option due to the way the networks are cut up. Basically, we have bits n pieces of class B's.

Since summerization is optional I may dump it.


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