hostname Router1
!
router bgp 40000
 bgp router-id 10.1.1.99
 bgp log-neighbor-changes
 timers bgp 70 120
 neighbor 192.168.1.1 remote-as 45000
 !
 address-family ipv4
  network 10.1.1.0 mask 255.255.255.0
  neighbor 192.168.1.1 activate
 exit-address-family

hostname Router2
!
router bgp 45000
 bgp router-id 172.17.1.99
 bgp log-neighbor-changes
 timers bgp 70 120
 neighbor 192.168.1.2 remote-as 40000
 !
 address-family ipv4
  network 172.17.1.0 mask 255.255.255.0
  neighbor 192.168.1.2 activate
 exit-address-family

Lab 2: IOS-XE BGP ipv4 address-family
IOS-XE Labs