BGP MED
- How trafic enters to your AS
- Transitive attribute
- lowest MED is preferable
- MED is exchanged between autonomous systems,
- MED is propagated to all routers within the neighbor AS but not passed along to any other autonomous systems.
Before:
R3(config-router-bgp)#show ip bgp
BGP routing table information for VRF default
Router identifier 192.168.23.3, local AS number 2
Route status codes: * - valid, > - active, # - not installed, E - ECMP head, e - ECMP
S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
Network Next Hop Metric LocPref Weight Path
* > 1.1.1.0/24 192.168.13.1 0 100 0 1 i
* 1.1.1.0/24 192.168.23.2 0 100 0 1 i
After
R3(config)#show ip bgp
BGP routing table information for VRF default
Router identifier 192.168.23.3, local AS number 2
Route status codes: * - valid, > - active, # - not installed, E - ECMP head, e - ECMP
S - Stale, c - Contributing to ECMP, b - backup, L - labeled-unicast
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
Network Next Hop Metric LocPref Weight Path
* > 1.1.1.0/24 192.168.23.2 500 100 0 1 i
* 1.1.1.0/24 192.168.13.1 700 100 0 1 i
R1
R1(config-router-bgp)#route-map MED permit 10
R1(config-route-map-MED)#set metric 700
R1(config-route-map-MED)#exit
R1(config)#router bgp 1
R1(config-router-bgp)#neighbor 192.168.13.3 route-map MED
% Incomplete command
R1(config-router-bgp)#neighbor 192.168.13.3 route-map MED out
R2
R2(config-router-bgp)#route-map MED permit 10
R2(config-route-map-MED)#set metric 500
R2(config-route-map-MED)#exit
R2(config)#router bgp 1
R2(config-router-bgp)#neighbor 192.168.23.3 route-map MED out