For the sake of getting familiar with BGP dampening (we're singly homed,
so I don't need this yet for our production network), I'm playing with BGP
dampening (damping?) on the EBGP link between work and home on two 2620s
both running 12.0(7)T. I'm following the guidelines of ripe-210
(http://www.ripe.net/ripe/docs/ripe-210.html) nearly to a T (I've added
our upstream /30 to the default-networks prefix-list just for safe
keeping, even though that announcement doesn't appear anywhere within our
BGP tables).
Office is ASN 65216, home is ASN 65101 (both private).
In a nutshell, suppress-value on 192.168.51.0/24 (my home lan) is 3000.
Half-life is 30, reuse-value is 750, max-suppress-time is 60. For some
reason, "penalty" never exceeds 3000 on the flapping prefix, so I never
see it get suppressed:
cisco5#sh ip bgp 192.168.51.0
BGP routing table entry for 192.168.51.0/24, version 1180
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Advertised to non peer-group peers:
216.136.28.64 216.136.28.66
65101
216.136.28.254 from 216.136.28.254 (216.136.28.65)
Origin IGP, metric 0, localpref 100, valid, external, best
Dampinfo: penalty 2399, flapped 8 times in 00:38:35
cisco2(config-subif)#shut
cisco5#sh ip bgp 192.168.51.0
BGP routing table entry for 192.168.51.0/24, version 1181
Paths: (1 available, no best path)
Flag: 0x208
Not advertised to any peer
65101 (history entry)
216.136.28.254 from 216.136.28.254 (216.136.28.65)
Origin IGP, metric 0, localpref 100, external
Dampinfo: penalty 3000, flapped 9 times in 00:38:48
Relevant bits of config from the office (where I'm watching the effects of
dampening):
router bgp 65216
no synchronization
bgp dampening route-map graded-flap-damping
neighbor 216.136.28.254 remote-as 65101
neighbor 216.136.28.254 default-originate
neighbor 216.136.28.254 distribute-list 2101 in
neighbor 216.136.28.254 distribute-list 2000 out
no auto-summary
!
ip prefix-list default-networks seq 5 permit 216.54.190.72/30
!
ip prefix-list max22 description Apply to /22 and /23 prefixes
ip prefix-list max22 seq 5 permit 0.0.0.0/0 ge 22 le 23
!
ip prefix-list min24 description Apply to /24 and longer prefixes
ip prefix-list min24 seq 5 permit 0.0.0.0/0 ge 24
!
route-map graded-flap-damping deny 5
match ip address prefix-list default-networks
!
route-map graded-flap-damping deny 10
match ip address prefix-list rootns
!
route-map graded-flap-damping permit 20
match ip address prefix-list min24
set dampening 30 750 3000 60
!
route-map graded-flap-damping permit 30
match ip address prefix-list max22
set dampening 15 750 3000 45
!
route-map graded-flap-damping permit 40
set dampening 10 1500 3000 30
!
I can't seem to find any caveats concerning this on the caveats list. Any
ideas what I'm doing wrong?
Pete
-- Peter J. Templin, Jr., CCNA, CCDA VP NetworkingOn-Line Internet Services - URDirect.net A division of Global On-Line Computers 5606 Randolph Blvd templin@urdirect.net San Antonio, TX 78233 (210)692-9911
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