BGP Dampening
- by default disabled
R2#show ip bgp dampening flap-statistics BGP table version is 7, local router ID is 192.168.12.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network From Flaps Duration Reuse Path *d 1.1.1.1/32 192.168.12.1 3 00:07:12 00:04:09 1 R2#R2#show ip bgp dampening dampened-paths BGP table version is 7, local router ID is 192.168.12.2 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete RPKI validation codes: V valid, I invalid, N Not found Network From Reuse Path *d 1.1.1.1/32 192.168.12.1 00:02:49 1 i R2#
Parameters
Every time route flaps it gets penalty 1000 by default
After the value is bigger thet supress penalty, the route will be supressed and will not be advertised
In case route flaps often there is limit - max supress penalty and max supress time
Every half-life time the penalty will be reduced by half, it takes place graddually over time
R2#show ip bgp dampening parameters
dampening 15 750 2000 60 (DEFAULT)
Half-life time : 15 mins Decay Time : 2320 secs
Max suppress penalty: 12000 Max suppress time: 60 mins
Suppress penalty : 2000 Reuse penalty : 750
R2#
2 options to config bgp dampening
- global
router bgp 2 bgp dampening - route-map
ip access-list standard R1_L0 permit 1.1.1.1 ! no cdp log mismatch duplex ! route-map DAMPENING permit 10 match ip address R1_L0 set dampening 15 750 2000 60 ! router bgp 2 bgp dampening route-map DAMPENING
Before/After
R2(config)#do show ip bgp 1.1.1.1
BGP routing table entry for 1.1.1.1/32, version 2
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
1
192.168.12.1 from 192.168.12.1 (1.1.1.1)
Origin IGP, metric 0, localpref 100, valid, external, best
R1(config)#int lo0
R1(config-if)#shut
R1(config-if)#no shut
R2(config)#do show ip bgp 1.1.1.1
BGP routing table entry for 1.1.1.1/32, version 3
Paths: (1 available, no best path)
Not advertised to any peer
Refresh Epoch 1
1 (history entry)
192.168.12.1 from 192.168.12.1 (1.1.1.1)
Origin IGP, metric 0, localpref 100, external
Dampinfo: penalty 1000, flapped 1 times in 00:00:04
R2(config)#
R2(config)#do show ip bgp 1.1.1.1
BGP routing table entry for 1.1.1.1/32, version 7
Paths: (1 available, no best path)
Not advertised to any peer
Refresh Epoch 1
1 (history entry)
192.168.12.1 from 192.168.12.1 (1.1.1.1)
Origin IGP, metric 0, localpref 100, external
Dampinfo: penalty 2688, flapped 3 times in 00:05:32
R2(config)#do show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.12.0/24 is directly connected, FastEthernet0/0
L 192.168.12.2/32 is directly connected, FastEthernet0/0
R2(config)#
start config R1
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface FastEthernet0/0
ip address 192.168.12.1 255.255.255.0
!
router bgp 1
network 1.1.1.1 mask 255.255.255.255
neighbor 192.168.12.2 remote-as 2
R2
interface FastEthernet0/0
ip address 192.168.12.2 255.255.255.0
router bgp 2
bgp log-neighbor-changes
bgp dampening
neighbor 192.168.12.1 remote-as 1