Kevin Dorrell, CCIE #20765

15 Feb 2008

NMC Lab 7.7 – BGP (Part 2)

Filed under: BGP — dorreke @ 21:39

Well, I put the question about the BGP dampening in NetPro, and I go three answers back.  Isn’t NetPro marvellous!  Anyway, it seems that if you are using a route-map to specify the dampening, then you have to specify the dampening parameters with a “set” in the route-map.  It will not assume the defaults.  So, my  route map should have looked like this:

route-map BGP-damped permit 10
 match ip address prefix-list BGP-damped
 set dampening 15 750 2000 60

The default parameters for bgp dampening are:

  • half-life = 15 mins
  • re-use = 750 seconds
  • suppress = 2000
  • max-suppress = 60 mins

That is, if you are applying dampening across the board, you can specify just bgp dampening and it will take those values.  Or you can supply your own values.

If, on the other hand, you want to apply dampening selectively, you must supply a route-map instead, but you must specify the values in the route-map.  There are no defaults.

BTW, you cannot dampen a locally generated aggregate.  Even if it flapping because the prefixes making it up are flapping, it does not appear in the show ip bgp dampening flap-statistics.

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