Hey all I have a fairly easy one for ya'll (I hope). I have a network consisting of multiple WAN Links which span all over the place. By WAN Links I am referring to private leased Layer 2 Circuits with Ethernet Hand offs.
Each of our client sites has two of these types of links via alternate providers back to our 2 main "hub" sites. I am currently running. IS-IS (Level 2) with MPLS LDP and BFD for failure detections on every single link. iBGP (MP-BGP) is how I exchange all NLRI between sites... that all works perfect. I'll start off by saying 90% of the failures on my network involve one of these links going down due to some fibre cut or other carrier transmission issue. This is usually no big deal. As the BFD will detect the fault within about 2 seconds and traffic re-routes instantly. I usually see a few packets drop during this time. For what I do. This is completely acceptable. However yesterday I was thrown a curveball. Rather than a particular link simply going down. I saw it flap constantly for 2-5 minutes. Which is far worse than I've experienced in the past. In the past this has happened, but wasn't as bad (as in wasn't noticable for my customer). My model has stood up ... until now. I understand what happened. I just don't know the best way to address the issue and prevent it from being customer impacting. The flaps i am referring to are NOT link state events. Meaning the interfaces don't actually change state (the issue is somewhere in my provider's end). Therefore I don't think "ip dampening" would help. What I want is something at the BFD, ISIS level. To essentially poison/penalize or even disable forwarding over link in question for a certain amount of time. Until stability is maintained. And if the flapping persists, to continue applying the penalty... (hope you all get what I am saying here) I looked into "BFD Dampening" which is configured under a template. But is this really going to give me the desired result? Is there something else out there that I've overlooked? If BFD damping is correct. I've got questions about the values :) Kind Regards Troy _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
