I am working at a client site today, and I may have to adjust the way some routes are propogated to the rest of the network. While examining the client config on this router which connects to the main MPLS circuit, I noticed the following in the bgp section:
router bgp 65002
neighbor 18.104.22.168 remote-as 7018
neighbor 22.214.171.124 timers 60 180
redistribute eigrp 13 metric 100 route-map eigrp-bgp-rm
neighbor 126.96.36.199 activate
network 172.16.132.8 mask 255.255.255.252
network 172.31.200.0 mask 255.255.255.0
network 192.168.38.1 mask 255.255.255.255
Why is this command used under BGP and what is its purpose?
There are many address-family types in bgp.
This "ipv4" address family just means that these configurations apply to ipv4 peering (which is the same as your legacy, basic, bgp peering).
This is where you would expect to see a configuration for peering to your internet ISP for the global, ipv4, routing table.
This newer format was added some time ago, and offers some simplicity in configuration for what would be more complex configuration scenarios.