I have a Cisco 7505 which is advertising about 50 routes to about 40 peers at mae-west, and a few others. One set of customers has been complaining that their connectivity is going away right at that router, and then coming back. Narrowed the set of customers down to a single CIDR block, at 204.147.224.0/20. So, some of our peers are claiming that the route is flapping... that's weird, we have them all nailed up to static routes... especially the CIDR blocks. So I wrote a tool which you can peer a router with, and it watches the BGP traffic and prints anything it gets, formatted, to standard out. My Cisco is sending fresh advertisements every 10-30 minutes for that route, and not for any other of the routes it has, and it appeared to be all the same, but on careful examination, it appears that each advertisement reflects a change in the MULTI_EXIT_DISC from 0x00000000 to 0x00000014 and then back again in the next advertisement. What the heck am I seeing here? Is someone's flap damping code seeing the repeated advertisements and suppressing me? Is my Cisco going crazy? -matthew kaufman matthew@scruz.net
In cisco.external.nanog you write:
I have a Cisco 7505 which is advertising about 50 routes to about 40 peers at mae-west, and a few others. One set of customers has been complaining that their connectivity is going away right at that router, and then coming back. Narrowed the set of customers down to a single CIDR block, at 204.147.224.0/20.
So, some of our peers are claiming that the route is flapping... that's weird, we have them all nailed up to static routes... especially the CIDR blocks. So I wrote a tool which you can peer a router with, and it watches the BGP traffic and prints anything it gets, formatted, to standard out.
My Cisco is sending fresh advertisements every 10-30 minutes for that route, and not for any other of the routes it has, and it appeared to be all the same, but on careful examination, it appears that each advertisement reflects a change in the MULTI_EXIT_DISC from 0x00000000 to 0x00000014 and then back again in the next advertisement.
add a default-metric under router bgp.. I think the source of the route in the routing table is changing for some reason and the box is conveying the metric as MED... --ravi
What the heck am I seeing here? Is someone's flap damping code seeing the repeated advertisements and suppressing me? Is my Cisco going crazy?
-matthew kaufman matthew@scruz.net
participants (2)
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matthew＠scruz.net -
Ravi Chandra