Question about routing table size on the route reflector

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Feb 20th, 2010
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Hello,


I am trying to understand the requirements of the route reflector's routing table size. Here is the scenario ;

- internet router is doing multihoming with three different ISPs. It is getting full internet routes from all of them.
- There are 25 PE routers in the topology.

How can i define the requirement of route reflector's IPv4 and VPNv4 routing table size ? 1 million , 2 million or

whatelse ???


Could you help me to understand the logic of this requirement? Kind Regards...


Burak Dikici

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Giuseppe Larosa Sun, 02/21/2010 - 23:57
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Hello Burak,

edge router may be multihomed with multiple upstream providers each of them sending a full BGP table.


However, the edge router will propagate to the route reflector server only its own best paths, not all the possible paths it has in its BGP table.

So you can think of 310,000 routes per edge router that is the current size of a full internet table.


If the edge router is only one you can calculate 500,000 routes for the internet table just to provide some space for future growth.


About the 25 PE nodes and the VPNv4 routes: the RRS doesn't need to take part in the VRFs so the use is just that of BGP.

I would not recommend to inject the full internet table into any VRF. The use of an internet gateway injecting a single default route into each interested MPLS VPN should be enough for common needs.

The internet gateway will have an interface in VRF and one in the global routing table.

Doing so the VPNv4 routes will be reduced to the minimum just the prefixes needed for inter-site connectivity.

You may need to send a full internet table in the VRF if you are providing Carrier supporting Carriers services.


A good choice could be a C7206 VXR with an NPE-G2 and 2GB of RAM to build your route reflector server.

An even more powerful device can be an ASR 1000 series router.



Hope to help

Giuseppe

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