Configuring the Address Family

The BGP multiprotocol extensions specify that BGP can exchange information within different types of address families. The JUNOSe BGP implementation defines the following different types of address families:

• Unicast IPv4—If you do not explicitly specify the address family, the router is configured to exchange unicast IPv4 addresses by default. You can also configure the router to exchange unicast IPv4 routes in a specified VRF.
• Multicast IPv4—If you specify the multicast IPv4 address family, you can use BGP to exchange routing information about how to reach a multicast source instead of a unicast destination. For information about BGP multicasting commands, see Configuring BGP Routing . For a general description of multicasting, see JUNOSe Multicast Routing Configuration Guide.
• VPN IPv4—If you specify the VPN-IPv4 (also known as VPNv4) address family, you can configure the router to provide IPv4 VPN services over an MPLS backbone. These VPNs are often referred to as BGP/MPLS VPNs. For detailed information, see Configuring BGP-MPLS Applications.
• Unicast IPv6—If you specify the IPv6 unicast address family, you can configure the router to exchange unicast IPv6 routes or unicast IPv6 routes in a specified VRF. For a description of IPv6, see JUNOSe IP, IPv6, and IGP Configuration Guide.
• Multicast IPv6—If you specify the multicast IPv6 address family, you can use BGP to exchange routing information about how to reach an IPv6 multicast source instead of an IPv6 unicast destination. For a general description of multicasting, see JUNOSe Multicast Routing Configuration Guide.
• VPN IPv6—If you specify the VPN-IPv6 address family, you can configure the router to provide IPv6 VPN services over an MPLS backbone. These VPNs are often referred to as BGP/MPLS VPNs.
• L2VPN—If you specify the L2VPN address family, you can configure the PE router for VPLS L2VPNs or VPWS L2VPNs to exchange layer 2 network layer reachability information (NLRI) for all VPLS or VPWS instances. Optionally, you can use the signaling keyword with the address-family command for the L2VPN address family to specify BGP signaling of L2VPN reachability information. Currently, you can omit the signaling keyword with no adverse effects. For a description of VPLS, see Configuring VPLS. For a description of VPWS, see Configuring VPWS.
• Route-target—If you specify the route-target address family, you can configure the router to exchange route-target membership information to limit the number of routes redistributed among members. For a description of route-target filtering, see Configuring BGP-MPLS Applications.
• VPLS—If you specify the VPLS address family, you can configure the router to exchange layer 2 NLRI for a specified VPLS instance. For a description of VPLS, see Configuring VPLS.
• VPWS—If you specify the VPWS address family, you can configure the PE router to exchange layer 2 NLRI for a specified VPWS instance. For a description of VPWS, see Configuring VPWS.

Any command issued outside the context of an address family applies to the unicast IPv4 address family by default.

To limit the exchange of routes to those from within the address family and to set other desired BGP parameters:

1. Access Router Configuration mode and create peers and peer groups. These peers and peer groups are in the default IPv4 address family.

   host1(config)#router bgp 100

   host1(config-router)#neighbor 10.10.2.2 remote-as 100

   host1(config-router)#neighbor 10.10.3.3 remote-as 100

   host1(config-router)#neighbor ibgp peer-group

2. In Router Configuration mode, create the address family within which the router exchanges addresses; this creation accesses Address Family Configuration mode.

   host1(config-router)#address-family vpn4 unicast

3. From within the address family, activate individual neighbors or peer groups to exchange routes from within the current address family. These peers or peer groups must first be created in the IPv4 address family.

   host1(config-router-af)#neighbor ibgp activate

4. If you have activated a peer group, from within the address family add peers as members of the peer group. These peers must first be created in the IPv4 address family.

   host1(config-router-af)#neighbor 10.10.2.2 peer-group ibgp

   host1(config-router-af)#neighbor 10.10.3.3 peer-group ibgp

5. From within the address family, configure BGP parameters for the address family.
6. Exit Address Family Configuration mode.

   host1:vr1(config-router-af)#exit-address-family

address-family

• Use to configure the router or VRF to exchange IPv4 or IPv6 addresses by creating the specified address family.
• IPv4 and IPv6 addresses can be exchanged in unicast, multicast, or VPN mode.
• The default setting is to exchange IPv4 addresses in unicast mode from the default router.
• Creating an address family for a VRF automatically disables both synchronization and automatic summarization for that VRF.
• This command takes effect immediately.
• Examples

  host1:vr1(config-router)#address-family ipv4 multicast

  host1:vr1(config-router)#address-family ipv4 unicast

  host1:vr1(config-router)#address-family ipv4 unicast vrf vr2

  host1:vr1(config-router)#address-family vpn4 unicast

  host1:vr1(config-router)#address-family ipv6 unicast

• Use the no version to disable the exchange of a type of prefix.
• See address-family.

bgp default ipv4-unicast

• Use to configure all neighbors to exchange addresses in the IPv4 unicast address family.
• All neighbors must be activated with the neighbor activate command in the IPv4 address family.
• Example

  host1:vr1(config-router)#bgp default ipv4-unicast

• Affects only neighbors created after you issue the command. To affect existing neighbors created before you issued the command, you must use the neighbor activate command in the context of the IPv4 unicast address family.
• Use the no version to disable the exchange of IPv4 addresses on all neighbors.
• See bgp default ipv4-unicast.

exit-address-family

• Use to exit Address Family Configuration mode and access Router Configuration mode.
• Example

  host1:vr1(config-router-af)#exit-address-family

• There is no no version.
• See exit-address-family.

neighbor activate

• Use to specify a peer or peer group with which routes of the current address family are exchanged.
• A peer or peer group can be activated in more than one address family. By default, a peer is activated only for the IPv4 unicast address family.
• The peer or peer group must be created in unicast IPv4 before you can activate it in another address family.
• If you specify a BGP peer group by using the peerGroupName argument, all the members of the peer group inherit the characteristic configured with this command unless it is overridden for a specific peer.
• The address families that are actively exchanged over a BGP session are negotiated when the session is established.
• This command takes effect immediately. If dynamic capability negotiation was not negotiated with the peer, the session is automatically bounced so that the exchanged address families can be renegotiated in the open messages when the session comes back up.

  If dynamic capability negotiation was negotiated with the peer, BGP sends a capability message to the peer to advertise or withdraw the multiprotocol capability for the address family in which this command is issued. If a neighbor is activated, BGP also sends the full contents of the BGP routing table of the newly activated address family.

• Example

  host1:vr1(config-router-af)#neighbor 192.168.1.158 activate

• Use the no version to indicate that routes of the current address family are not to be exchanged with the peer. Use the default version to remove the explicit configuration from the peer or peer group and reestablish inheritance of the feature configuration.
• See neighbor activate.

If you have configured some or all neighbors to be in the multicast or VPN-IPv4 address families, you can quickly configure all neighbors to be part of the IPv4 unicast address family by issuing the bgp default ipv4-unicast command.

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