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Monday, November 29, 2010

Question 177

What path attributes would you use to manipulate where outgoing traffic exits?

2 comments:

networkdongle said...

WEIGHT and Local Preference


DEFAULT BGP and ROUTING TABLE:

R1#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
* 4.4.4.4/32 13.13.13.3 0 3 4 i
*> 12.12.12.2 0 2 4 i

R1#sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 2, type external
Last update from 12.12.12.2 00:07:00 ago
Routing Descriptor Blocks:
* 12.12.12.2, from 12.12.12.2, 00:07:00 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 2


R1#sh run | s bgp
router bgp 1
network 1.1.1.1 mask 255.255.255.255
neighbor 12.12.12.2 remote-as 2
neighbor 13.13.13.3 remote-as 3


WEIGHT:

R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config-router)#neighbor 13.13.13.3 weight 1
R1(config-router)#do clear ip bgp * soft in

R1(config-router)#do sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*> 4.4.4.4/32 13.13.13.3 1 3 4 i
* 12.12.12.2 0 2 4 i

R1(config-router)#do sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 3, type external
Last update from 13.13.13.3 00:00:36 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:00:36 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 3


LOCAL PREF:
R1(config)#route-map LOCAL_PREF
R1(config-route-map)#set local-preference 101
R1(config-router)#neighbor 13.13.13.3 route-map LOCAL_PREF in
R1(config-route-map)#do sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*> 4.4.4.4/32 13.13.13.3 101 0 3 4 i
* 12.12.12.2 0 2 4 i

R1(config-route-map)#do sh ip route 4.4.4.4
Routing entry for 4.4.4.4/32
Known via "bgp 1", distance 20, metric 0
Tag 3, type external
Last update from 13.13.13.3 00:00:37 ago
Routing Descriptor Blocks:
* 13.13.13.3, from 13.13.13.3, 00:00:37 ago
Route metric is 0, traffic share count is 1
AS Hops 2
Route tag 3

Packets Analyzed said...

That is correct. Nice example

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