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VRF-Lite and Cisco 3800 ISR

Unanswered Question
Jul 11th, 2006
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Can someone please help answering my following questions:

Question 1: what is the max no. of VRFs that can be defined on Cisco 3800 ISR? And how much memory do we need to support the max no. of VRFs on 3800?

Question 2: is there any Cisco documentation on this fact?

Thanks so much for any assistance.


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Overall Rating: 3 (3 ratings)
sultan-shaikh Tue, 07/11/2006 - 23:06
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I can tell you from my testing/experience... the maximum no. of VRFs I had configured on 3800 was 75, I could have created more than that but my scalability requirements were more than met by the same.

Actually the limiting factor is memory that you have on the router, as VRFs are nothing but routing tables, which ultimately require memory.

FYI, I too wasn't able to find any related documents anywhere.



romccallum Wed, 07/12/2006 - 05:10
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Hi mate,

you would be better firing that question to your allocated SE team. They will find that info for you, tho what i can tell you is that device can support 8000000000000 vrfs just as long as they dont have any routes in them ;-). Your biggest factor is how many routes are held within the tables of this device as already stated. Also how many routes does your global routing table have. Other features that you enable, say QOS, TE, Multicast - these all have a limiting factor on the life of your device so thats why you dont see any documentation produced. It would have to be so generic that it would be worthless for every company that requires it.


pnschurr Wed, 07/12/2006 - 16:19
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I've had some experience in trying to characterise scalability of PE's before - due to other vendors problems.

The thing with Cisco and how the software deploys vrf's and vrf routing tables and routing process is that they do it with indexing.

There are no separate routing tables or CEF tables per vrf. All routing information is kept in a common store, but it is indexed by vrf. That same goes for routing protocols, when OSPF runs for a vrf, it is the same OSPF process but it runs for an indexed set of data in the database and outputs indexed data for the routing table.

In terms of CEF, there is no separation in CEF for vrfs. Every route in every vrf has a unique label assigned (platform specific) and therefore has a unique entry in CEF.

So for quantifying scalability, you can look at how many total routes you're going to see, how many routing processes you're going run (remember that OSPF is 1 for many vrf's for instance except that it may actually run more often as it has to cover more routing sets), and go from there. It is largely irrelevant how many vrf's are defined or how many vrf's the total load of routes is spread across.


pnschurr Wed, 07/12/2006 - 16:22
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And I just realised that you mentioned vrf-lite in your topic, so ignore the label reference above.



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