BGP full routes memory requirements

Unanswered Question
May 14th, 2008

Hi all

Before I request my ISP to send me a full routing table - does anyone know if we'll be able to fit a single copy into 90MB free memory (Cisco 3825)?

Thanks

I have this problem too.
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To store a complete global BGP routing table from one BGP peer, it is best to have a minimum of 512 MB of RAM in the router. If 256 MB of RAM is used, it is recommended that you use more route filters. If you use 512 MB of RAM, more Internet routes can be placed in the routing table with fewer route filters.

There may be convergence and memory allocation issues running less than 512MB.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a83.shtml#bgpreceivedtable

Hope this helps

Martin

mheusing Wed, 05/14/2008 - 06:24

Hi,

Please also be aware, that the BGP table alone will not help you. You need additional memory for the RIB and for CEF. To get an idea about memory consumption in real BGP routers login to a route-server (links are f.e. on traceroute.org) and check with "show ip bgp summary. You will see between 40M and 650M BGP table - depending on the number of pathes - and likely additionally more than 40M for RIB and CEF. Also take into account, that you need some free memory for normal IOS operation. So your 3825 needs more memory and you should follow the recommendation of the other Martin :-)

Hope this helps! Please use the rating system.

Regards, Martin

guruprasadr Wed, 05/14/2008 - 07:28

HI, [Pls Rate all Informative POST]

Current "Global Internet Routing Table size" is around 2 Lac 48 Thousand Prefixes.

So, in this case, if you are going to receive all the above means atleast a 7206VXR with NPEG-2 is required to handle with Higer Memory. In additon to the size of the Routing table, it requries the CEF table to be processed.

Normally, i have seen in a scenario: My Customer was running 3800 Series Router and receiving the Entire Internet Routing Table, later-days the problem happened was "MALLOC" Failure, where the CEF Process is automatically disabled.

SO, better recommendation to Upgraded with a Higher Version like 7206 Series.

Hope I am Informative.

Pls RATE all INFORMATIVE Post

Best Regards,

Guru Prasad R

rais Wed, 05/14/2008 - 07:53

Currently one of 7206 routers shows following bytes:

Prefixes Current:

5 254763 (Consumes 13247572 bytes)

But as pointed earlier this is only for perfixes. On this router used processor memory is 245945908 (b). Total is 2GB.

Thanks.

osiristrading123 Wed, 05/14/2008 - 13:44

Thanks to all for the replies. We will upgrade the router to 768MB in order to take the routing table.

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