BGP aggregation

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Apr 27th, 2010
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Guys i have two subnets as under and i want to aggregate them in BGP but dont know what

would be the aggregation address if someone plz help me out....secondly i have to put ip prefix list as well for these networks so what would be that like le 32 etc /27 /28

Thanks guys

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Giuseppe Larosa Tue, 04/27/2010 - 07:13
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Hello Khan,

you need to write down in binary the last byte and you need to find out the last matching bit in base addresses

160 = 128 +32  ->  1010 0000

32                         0010 0000

the only possible aggregate that covers both IP prefixes but also other possible prefixes is:   because first bit of 4th byte is different in the two base addresses

this is called a non exclusive summary route

in BGP you can use

router bgp xx

aggregate-address mask

if this is not acceptable for you, you should advertise the IP single subnets

Hope to help



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