VPNv4 route switch time

[chenleish]

if conside router A/router B/router C is 3 PE,is MP-BGP peer.

CE1 connect to router A & B ,use static route.

CE2 connect to router C,use static route.

1) use same rd,C choose CE2's route from the best: if A connect to CE1 is down,how much time will C switch to route from B? 15s? IF router A is crash how much time?

2)use diffent rd,will C switch with no stop forwarding ?

[fukusho]

Hi,

I'm not sure if I read your question correctly but let me try.

for 1), assuming that router C chooses router A for bgp nexthop, since RD's are the same then I believe that router C will change the bgp nexthop to router B when bgp withdraw message is received from router A.

I really cannot tell you how much time it will take(you should actually test it yourself), but I believe it will take several seconds.

If router A crashes, assuming that router A,B,C are not directly connected, it will depend on the following three conditions;

1.IGP route convergence

2.BGP holddown timer

3.BGP scan timer

(not applicable if BGP Support for Next-Hop Address Tracking is supported)

Usually IGP convergence will override the BGP holddown timer, so I guess IGP convergence time(depends on what you use) will be the case.

for 2), router C has both routes but unless you're not load-sharing, it still has to receive bgp withdraw to fallover to router A to B.

hope this helps.