about BGP time

[chenleish]

If A B C is EBGP peer,A B have static route to 10.0.0.1 and advertise it to C,C choose the route from A as best path. when A's connnection to 10.0.0.1 is down, in theory,how much time would C change to choose the route from B?

AND how about A is crash?

how about A B C is IBGP peer?

or A B C is MP-bgp peer,and 10.0.0.1 is the VPNV4 route?

[suresh.krishnamurthy]

Hi,

Answer to Q1:

"C" choose the route from "B" almost immediately(which is already in BGP database) as soon as "A"withdraws the unfeasible route by triggered update.

Answer to Q2:

If A crashes "C" waits until holdtimer (180 secs- or 3 keepalive misses)and chooses route from "B"

Answer to Q3:

Either iBGP or eBGP it doesn't matter. chaangeover is same as ans 1/2. (In this case IGP is also taken into consideration as Admn.Distance (Protocol Priority) of iBGP routes are very high (200) when compared to IS-IS (115) or RIP (120) or OSPF (110).

Answer to Q4:

1. MP-BGP is used in RFC2547bis BGP/MPLS based VPNs.

Normally MP-BGP is run between Provider edge(PE) routers. A VPN site is normally serviced by one PE router to avoid complications in routing.

VPNV4 route 10.0.0.1 on router A & 10.0.0.1 on Router B should not be same if it belong to same VPN.

2. If it belongs to different VPNs by prefixing Route distinquishers it will look like different routes and populate different VRFs of Router "C"with the help of Route targets.

There is no question of choosing between the two in the second case.

Regards

Krishnamurthy Suresh

[chenleish]

thanks for the reply.

but for Q1: I think it will wait for the bgp scanner time which is most 60s,so it will wait for 1s-60s to change to the route from B,am i right?

Q2 no question

Q3 no question

Q4: In one VPN , if you conside redundancy solution for the customer, one for primary use,the other for backup,it will be two same route from two different PE.