ELTEX ESR-3100 - BGP Best Route Selection Policy

ESR series service routers.ESR-Series. User manual
276
Enable IPv4 route exchange:
esr-R3(config-bgp-neighbor)# address-family ipv4 unicast
esr-R3(config-bgp-neighbor-af)# enable
esr-R3(config-bgp-neighbor-af)# exit
esr-R3(config-bgp-neighbor)# exit
Create a neighborhood with the R1 router via eBGP:
esr-R3(config-bgp)# neighbor 185.0.0.2
esr-R3(config-bgp-neighbor)# remote-as 20
esr-R3(config-bgp-neighbor)# enable
Enable the exchange of ipv4 routes, permitting the necessary routes for advertising by means of a previously
prepared route-map:
esr-R3(config-bgp-neighbor)# address-family ipv4 unicast
esr-R3(config-bgp-neighbor-af)# route-map bgp-general out
esr-R3(config-bgp-neighbor-af)# enable
esr-R3(config-bgp-neighbor-af)# exit
esr-R3(config-bgp-neighbor)# exit
Enable protocol operation:
esr-R3(config-bgp)# enable
esr-R3(config-bgp)# exit
To view BGP peers information, use the following command:
esr# show bgp neighbors
To view BGP routing table, use the following command:
esr# show bgp ipv4 unicast
11.5.3 BGP best route selection policy
During operation, BGP calculates one best route to each received subnet. If there is no higher priority route
learned by another routing protocol before this subnet, then the route is installed in the routing table.
Algorithm of best route selection in BGP is given below.
If ECMP mechanism is enabled (router maximum-paths ..),then the routing table can get up to 16
active routes to the same subnet.
When advertising BGP to peers, the attributes of the best route will be used.

The algorithm is used for the following address family: unicast IPv4, unicast IPv6, VPNv4 unicast,
VPLS.
