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02-07-2013 02:41 AM - edited 03-04-2019 06:58 PM
Hi All,
Please help me to calculate the BGP table size in terms of memory required, I got the information from looking glass. Guide my which components i need to add and than calculate the memory size required.
BGP table version is 262538329, main routing table version 262538329
454321 network entries using 53155557 bytes of memory
908642 path entries using 47249384 bytes of memory
98794/69504 BGP path/bestpath attribute entries using 12250456 bytes of memory
51 BGP rrinfo entries using 1224 bytes of memory
86096 BGP AS-PATH entries using 2220164 bytes of memory
70 BGP community entries using 1924 bytes of memory
20 BGP extended community entries using 496 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 114879205 total bytes of memory
BGP activity 14224881/13758829 prefixes, 70150237/69218155 paths, scan interval 60 secs
If i would be multihomeing with two ISPs with full BGP table and than how should I calculate the memory requirement for router?
Thanks In advance.
Jagdev
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02-07-2013 07:55 AM
Hello Jagdev,
an exact calculation is not so important as memory chips come in discrete pieces (256 MB, 512MB, 1GB and so on)
However, you can make a reasonable guess by doubling the memory used by BGP for two BGP full tables ( it will be more then the effective use) and by counting only one the prefixes in the CEF table as only the best path goes in the CEF table.
Note also that the line you have mentioned is only the memory used for the IP prefixes not all the memory used by BGP
>> BGP using 114879205 total bytes of memory
and
>> 454321 network entries using 53155557 bytes of memory
AS paths and all other BGP attributes need to be stored too, as the various lines of the show output show..total memory used by BGP is the first line.
Hope to help
Giuseppe
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02-07-2013 05:21 AM
Hello Jagdev,
there is a line with total memory used by BGP
>> BGP using 114879205 total bytes of memory
However, this is only a part of the story: CEF tables use quite a memory for each IPv4 prefix in addition to the memory used by BGP. ( 1 kbyte for each IPv4 prefix)
A BGP full table is around 420000 IPv4 prefixes
Your router should have at least 1 GB of RAM for multihoming as a safe assumption
Hope to help
Giuseppe
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02-07-2013 06:08 AM
Hello Giuseppe
Thanks for your response, Can you please guide me how should i calculate the memory, like you explained for CEF
454321 network entries using 53155557 bytes of memory would have required 454321kbyte for CEF,
How much would for one BGP table and other thing than which parameters would required double as there will be dual ISP and router would be learning the BGP information from two eBGP peers.
I want to understand the method to calculate it
Thanks
Jagdev
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02-07-2013 07:55 AM
Hello Jagdev,
an exact calculation is not so important as memory chips come in discrete pieces (256 MB, 512MB, 1GB and so on)
However, you can make a reasonable guess by doubling the memory used by BGP for two BGP full tables ( it will be more then the effective use) and by counting only one the prefixes in the CEF table as only the best path goes in the CEF table.
Note also that the line you have mentioned is only the memory used for the IP prefixes not all the memory used by BGP
>> BGP using 114879205 total bytes of memory
and
>> 454321 network entries using 53155557 bytes of memory
AS paths and all other BGP attributes need to be stored too, as the various lines of the show output show..total memory used by BGP is the first line.
Hope to help
Giuseppe
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02-07-2013 10:53 PM
Thanks Giuseppe,
I was not concerned about memory chips, i already going to get 1GB ones, but i wanted to know how should i calculate the memory. If i am planing to implement it should know about this as much as i can.
Thanks once again.
JD