router bgp 4
 neighbor 10.4.1.2 remote-as 6
 neighbor 10.5.1.1 remote-as 5
 neighbor 10.4.3.2 remote-as 1
 address-family ipv4 unicast
  neighbor 10.4.1.2 activate
  neighbor 10.5.1.1 activate
  neighbor 10.4.3.2 activate
  network 10.4.0.0 mask 255.255.0.0
  redistribute connected
  aggregate-address 10.4.0.0 255.255.0.0 summary-only
  no auto-summary