HITTING
BGP TIMERS (HOLD-TIME, SCAN TIME, UPDATE-TIME)
Range of AS 1 -65535 [public uses 1-64511] [private uses
64512-65535]
Default keep-alive is 60s and Holdtime is 180s
Default update(advertisement) is 5s(ibgp) and 30s(EBGP)
Default bgp scan time is 60s
We need BGP if we need to connect to more than 1 service provider
or we are a transit AS
Assuming bgp has already been configured, I would only point
out some key points. These are my default configs
r1
int s0/0
ip add 10.1.13.1 255.255.255.0
no shut
int f0/0
ip add 192.168.1.1 255.255.255.0
no shut
int lo 0
ip add 1.1.1.1 255.255.255.255
no shut
exit
router ospf 1
network 10.1.13.0 0.0.0.255 area 0
network 192.168.1.0 0.0.0.255 area 0
network 1.1.1.1 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0
r2
int s0/0
ip add 10.1.12.1 255.255.255.0
no shut
int f0/0
ip add 192.168.2.1 255.255.255.0
no shut
int lo 0
ip add 2.2.2.2 255.255.255.255
no shut
exit
router ospf 1
network 10.1.12.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0
network 2.2.2.2 0.0.0.0 area 0
exit
router bgp 100
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0
r3
int s0/1
ip add 10.1.12.2 255.255.255.0
no shut
int s0/0
ip add 10.1.13.2 255.255.255.0
no shut
int f0/0
ip add 10.1.10.2 255.255.255.0
no shut
int lo 0
ip add 3.3.3.3 255.255.255.255
no shut
exit
router ospf 1
network 10.1.13.0 0.0.0.255 area 0
network 10.1.12.0 0.0.0.255 area 0
network 3.3.3.3 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0
nei 4.4.4.4 remote-as 100
nei 4.4.4.4 update-source lo 0
r4
int f0/0
ip add 192.168.1.2 255.255.255.0
no shut
int f0/1
ip add 192.168.2.2 255.255.255.0
no shut
int lo 0
ip add 4.4.4.4 255.255.255.255
no shut
exit
router ospf 1
network 192.168.1.0 0.0.0.255 area 0
network 192.168.2.0 0.0.0.255 area 0
network 4.4.4.4 0.0.0.0 area 0
exit
router bgp 100
nei 2.2.2.2 remote-as 100
nei 2.2.2.2 update-source lo 0
nei 3.3.3.3 remote-as 100
nei 3.3.3.3 update-source lo 0
nei 1.1.1.1 remote-as 100
nei 1.1.1.1 update-source lo 0
Now lets get to the problems.
1) Cfg timers on R3 to use hold timer of
21seconds
R3(config)#router bgp 100
#timers bgp 7 21 {that’s it}
#timers bgp 7 21 {that’s it}
Now how to we view our changes.
R3#clear ip bgp * [dont do this
in a production network]
R3#sh ip bgp nei 1.1.1.1
Configured hold time is 21,keepalive interval is 7
seconds, Minimum holdtime from neighbor is 0 seconds
R1#sh ip bgp nei 3.3.3.3
hold time is 21, keepalive interval is 7 seconds
This takes into the assumption
that R1 was configured with the default values
2) Lets configure R1 to use a hold time of
90s.Remember Routers will use the lower hold-time
R1(conf)#router bgp 100
#timers bgp 30 90
#do clear ip bgp *
#do clear ip bgp *
R1#sh ip bgp nei 3.3.3.3
Last read 00:00:03, last write
00:00:03, hold time is 21, keepalive interval is 7 seconds
Configured hold
time is 90, keepalive interval is 30 seconds, Minimum holdtime from neighbor is
0 seconds
3)
Change the scan time on R3 to 50s
R3(conf)#router bgp 100
#bgp scan-time 50
To verify,
R3#sh ip bgp summary
BGP activity 4/3 prefixes, 4/3 paths, scan interval 50
secs
4)
Cfg R3
such that it send adverts(updates) to R1 very 3s
R3(conf)#router bgp 100
#nei 1.1.1.1 advertisement-interval 3
#do clear ip bgp *
To view changes made
#sh ip bgp nei 1.1.1.1
Scroll down to For address family: IPv4 Unicast
Minimum time between advertisement runs is 3 seconds
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