Ali -
Vernon's comments in his previous response were essentially correct and I was imprecise. If the failure of R4 takes down the link between R3 and R4 - the failure of the link will be immediately detected at R3 by virtually every protocol (except static routing) and propagate quickly. If the link is something like a shared Ethernet, then older routing protocols (e.g.,
) may take some time to recover because they lack a "heartbeat" mechanism, and can only detect the failure by the absence of periodic updates from the neighbor.
So the answer, as always, is "it depends" :)
/Michel
-----Original Message-----
From: Ali Boudani [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, February 13, 2002 6:49 AM
To: [EMAIL PROTECTED]
Subject: Simple question
If we have the following figure:
R1---------R2---------R3---------R4 where R1 to R4 are unicast routers.
R1 is sending packets to R4. If R4 goes down, when R1 will detect this??
Before sending packets or after?
