From: David Wolsefer (dwolsefer@xxxxxxxx)
Date: Mon Jan 29 2001 - 16:49:45 GMT-3
Here is the answer you seek.
Regards,
David Wolsefer, CCIE #5858
-----Original Message-----
From: David Wolsefer [mailto:dwolsefer@wams.com]
Sent: Friday, January 12, 2001 4:40 PM
To: Harbir Kohli
Cc: ccielab@groupstudy.com
Subject: RE: bgp question
Here is a real world dampening config. Alternatively, you can see Sam
Halabi's book "Internet Routing Architectures", p. 432 in the 2'nd edition.
The command syntax is as follows:
bgp dampening [[route-map map-name] [half-life-time reuse-value
suppress-value maximum-suppress-time]]
- half-life-time is in the range of 1 to 45 minutes. The current default is
15 minutes.
- reuse-value is in the range of 1 to 20000. The default is 750.
- suppress-value is in the range of 1 to 20000. The default is 2000.
- maximum-suppress-time is the maximum duration that a route can be
suppressed. The range is 1 to 255. The default is 4*half-life time.
Cheers,
David Wolsefer, CCIE #5858
! Enable our dampening parameters. See the route map and prefix-lists
! below.
bgp dampening route-map graded-flap-dampening
!
! Now we configure our prefix lists for our dampening requirements.
! These are configured along the lines of the recommendations made
! by RIPE. The goal is to minimalize the effect of dampening on
! the shorter and historically more stable prefixes as well as the
! netblocks that contain DNS root servers. The longer prefixes
! are dampened for longer periods of time, as these have been the
! the source of a greater percentage of the instability in the
! global routing table.
! Note that a longer prefix equates to a less-aggregated and smaller
! netblock.
!
! The damplongprefixes list is for prefixes of /24 and longer.
ip prefix-list damplongprefixes description Prefixes of /24 and longer.
ip prefix-list damplongprefixes seq 5 permit 0.0.0.0/0 ge 24
!
! The dampmediumprefixes list is for prefixes of /22 and /23.
ip prefix-list dampmediumprefixes description Prefixes of /22 and /23.
ip prefix-list dampmediumprefixes seq 5 permit 0.0.0.0/0 ge 22 le 23
!
! The dampshortprefixes list is for prefixes of /21 and shorter.
ip prefix-list dampshortprefixes description Prefixes of /21 and shorter.
ip prefix-list dampshortprefixes seq 5 permit 0.0.0.0/0 le 21
!
! The rootservers prefix list is to prevent dampening of
! the root DNS server netblocks.
ip prefix-list rootservers description DNS root server netblocks.
ip prefix-list rootservers seq 5 permit 198.41.0.0/24
ip prefix-list rootservers seq 10 permit 128.9.0.0/16
ip prefix-list rootservers seq 15 permit 192.33.4.0/24
ip prefix-list rootservers seq 20 permit 128.8.0.0/16
ip prefix-list rootservers seq 25 permit 192.203.230.0/24
ip prefix-list rootservers seq 30 permit 192.5.4.0/23
ip prefix-list rootservers seq 35 permit 192.112.36.0/24
ip prefix-list rootservers seq 40 permit 128.63.0.0/16
ip prefix-list rootservers seq 45 permit 192.36.148.0/24
ip prefix-list rootservers seq 50 permit 193.0.14.0/24
ip prefix-list rootservers seq 55 permit 198.32.64.0/24
ip prefix-list rootservers seq 60 permit 202.12.27.0/24
!
! We apply our dampening prefix-lists with our route-map entries.
! Don't dampen the rootservers prefix-list.
route-map graded-flap-dampening deny 10
match ip address prefix-list rootservers
! Dampen the /24 and greater prefixes for a maximum of 60 minutes.
route-map graded-flap-dampening permit 20
match ip address prefix-list damplongprefixes
set dampening 30 750 3000 60
! Dampen the /22 to /23 prefixes for a maximum of 45 minutes.
route-map graded-flap-dampening permit 30
match ip address prefix-list dampmediumprefixes
set dampening 15 750 3000 45
! Dampen the /21 and shorter prefixes for a maximum of 30 minutes.
route-map graded-flap-dampening permit 40
match ip address prefix-list dampshortprefixes
set dampening 10 1500 3000 30
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