Comment Re:Allocation (Score 2, Informative) 185
care to explain that one?
each entry requires (at the very minimum) prefix, netmask and nexthop. this is before you remember it's bgp, and has to hold a whole host of other shit (communities, as-path, metric, localpref, weight, origin etc).
i make that:
2^24
= 16777216 /24s
16777216*96
= 1610612736 bits for prefix,mask,nexthop
1610612736/8
= 201326592 bytes for the very basics
You can safely double that (at the very least) to factor extra bgp overhead gubbins. Take a third off for route compression, and double that figure if you wanna run soft reconfiguration inbound. That comes out on the sunny side of half a gig for just your bgp table.
also, remember that your $12 stick of RAM will cost $1500 if you're buying ram direct from a router vendor (many refuse to support devices unless you use their propriatory labelled RAM). add on 50 meg for the OS itself and a random amount for your IGP and you're talking about needing a router with a gig of ram.
then think how long it'll take for you to learn this 200 meg routing table. bgp convergence is bad at the best of times, but adding 200 mbyte overhead when you start a bgp session is just ridiculous.
there's a reason why route aggregation is a good thing. and it's precisely because of the 'inherent cost and/or complexity of management'
HTH & HAND
each entry requires (at the very minimum) prefix, netmask and nexthop. this is before you remember it's bgp, and has to hold a whole host of other shit (communities, as-path, metric, localpref, weight, origin etc).
i make that:
2^24
= 16777216
16777216*96
= 1610612736 bits for prefix,mask,nexthop
1610612736/8
= 201326592 bytes for the very basics
You can safely double that (at the very least) to factor extra bgp overhead gubbins. Take a third off for route compression, and double that figure if you wanna run soft reconfiguration inbound. That comes out on the sunny side of half a gig for just your bgp table.
also, remember that your $12 stick of RAM will cost $1500 if you're buying ram direct from a router vendor (many refuse to support devices unless you use their propriatory labelled RAM). add on 50 meg for the OS itself and a random amount for your IGP and you're talking about needing a router with a gig of ram.
then think how long it'll take for you to learn this 200 meg routing table. bgp convergence is bad at the best of times, but adding 200 mbyte overhead when you start a bgp session is just ridiculous.
there's a reason why route aggregation is a good thing. and it's precisely because of the 'inherent cost and/or complexity of management'
HTH & HAND
