[c-nsp] Sizing a router for full feed (once and for all)

[Marko Milivojevic]

	I must corret myself. I missed the "path entries" and some other tables in 
BGP - my bad. Calculation then changes a little bit and each "prefix" (for 
the sake of simplicity) is using around 205 bytes.

Marko.

Marko Milivojevic wrote:
> Once and for all, huh? :-)
> 
> I will take example of one of the routers I'm operating. It has a mix of two 
> full BGP feeds + customer and our own routes.
> 
> Each BGP prefix is using 115 bytes on average (with some communities). 
> Multiply that by number of prefixes received and full views, and you get the 
> amount that BGP alone would consume. Based on this information, routing and 
> CEF tables are built (more memory used). Exact calculation is very much 
> topology-based (you may have 4 full views and use less memory than with only 
> two feeds in some cases). But, the key point is, if your 
> router/switch/whatever can't have the full BGP table multiplied by, say, 2.5 
> (routing and CEF tables), you shouldn't really try it.
> 
> Marko.
> 
> P.S. It's really not that simple.
> 
> Joost greene wrote:
>> Hello,
>>
>> I always see people asking if their routers can handle BGP and alot of times
>> the answer isnt just memory, sometimes TCAM limitation (3750 for e.g.) maybe
>> other cases, what i want to have is some sort of check list for this, my
>> case is a :
>>
>>
>>
>> IOS (tm) 3700 Software (C3745-JK9O3S-M), Version 12.3(9), RELEASE SOFTWARE
>> (fc2)
>> System image file is "flash:c3745-jk9o3s-mz.123-9.bin"
>>
>> cisco 3745 (R7000) processor (revision 2.0) with 250880K/11264K bytes of
>> memory.
>> R7000 CPU at 350MHz, Implementation 39, Rev 3.3, 256KB L2, 2048KB L3 Cache
>> 2 FastEthernet/IEEE 802.3 interface(s)
>> 8 Serial network interface(s)
>> DRAM configuration is 64 bits wide with parity disabled.
>> 151K bytes of non-volatile configuration memory.
>> 125184K bytes of ATA System CompactFlash (Read/Write)
>> 125184K bytes of ATA Slot0 CompactFlash (Read/Write)
>>
>>
>> I want to know if it can handle two full tabes and more than that how do i
>> do this math next time ?
>>
>> Thanks
>> Joost
>> _______________________________________________
>> cisco-nsp mailing list  cisco-nsp at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/cisco-nsp
>> archive at http://puck.nether.net/pipermail/cisco-nsp/
>>
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>