“The primary function of a Border Gateway Protocol (BGP) speaking system is to exchange network reachability information with other BGP systems. This network reachability information includes information on the list of Autonomous Systems (ASes) that reachability information traverses. This information is sufficient for constructing a graph of AS connectivity for this reachability, from which routing loops may be pruned and, at the AS level, some policy decisions may be enforced.” –rfc4271A
BGP is configurable to run in either internal (iBGP) or external (eBGP) mode.
Create a static route towards a blackhole interface:
switch(config)# ip route IP-ADDR/SUBNET blackhole
Configure a BGP instance:
switch(config)# router bgp AS-NUM [vrf VRF]
Create network statements for each subnet to advertise:
switch(config-router)# network IP-ADDR/SUBNET
Configure a neighbor relationship with another BGP speaker:
switch(config-router)# neighbor IP-ADDR remote-as AS-NUM
Configure an MD5 encrypted password to secure the neighbor relationship:
switch(config-router)# neighbor IP-ADDR password <cipher|plain>text PSWD
Configure soft reconfiguration:
switch(config-router)# neighbor IP-ADDR soft-reconfiguration inbound
Show commands to validate functionality: :
show bgp all [summary|neighbors]