Configuring Route Exchange Between the PE and CE

Context

The Hub-PEs and Hub-CEs can use IGP or EBGP to exchange routing information. When they use EBGP, you must configure the Hub-PEs to allow repeated local AS number.

As shown in Figure 1, the routing information advertised by a Spoke-CE is forwarded to the Hub-CE and Hub-PE before being transmitted to other Spoke-PEs. If EBGP runs between the Hub-PE and the Hub-CE, the Hub-PE performs the AS-Loop detection on the route. If the Hub-PE detects its own AS number in the route, it discards the route. In this case, to implement the Hub and Spoke networking, the Hub-PE must be configured to permit the existence of repeated local AS numbers.

Figure 1 EBGP running between the Hub-CE and Hub-PE

Procedure

Configure EBGP between the Hub-PE and Hub-CE.
For detailed configuration, see Configuring a Routing Protocol Between PE and CE.

In this way, EBGP, IGP, or static routes can be adopted between the Spoke-PE and the Spoke-CE.

To set up the EBGP peer between the Hub-PE and the Hub-CE and between the Spoke-PE and Spoke-CE, perform the following steps on the Hub-PE:
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Run ipv6-family vpn-instance vpn-instance-name
  The BGP VPN instance IPv6 address family view is displayed.
4. Run peer { group-name | ipv6-address } allow-as-loop [ number ] [ global-as [ vpn-as ] ]
  The routing loop is allowed.
  
  Here the value of number is set as 1, which means the route with the AS repeated once can be sent.
Configure IGP between the Hub-PE and Hub-CE.
For detailed configuration, see Configuring a Routing Protocol Between PE and CE.

Only IGP or static routes can be used between the Spoke-PE and Spoke-CE. BGP can cause route flapping between them.
Configure static routes between the Hub-PE and Hub-CE.
For detailed configuration, see Configuring a Routing Protocol Between PE and CE.

In this way, EBGP, IGP, or static routes can be adopted between the Spoke-PE and the Spoke-CE.

If the Hub-CE uses the default route to access the Hub-PE, to advertise the default route to all the Spoke-PEs, perform the following steps on the Hub-PE:
1. Run system-view
  The system view is displayed.
2. Run ipv6 route-static vpn-instance vpn-instance-name :: 0 nexthop-ipv6-address [ tag tag ] [ description text ]
  The default route is configured.
  
  Here, vpn-instance-name refers to the VPN-out. nexthop-ipv6-address is the IPv6 address of the Hub-CE interface that is connected to the PE interface bound with the VPN-out.
3. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
4. Run ipv6-family vpn-instance vpn-instance-name
  The BGP VPN instance IPv6 address family view is displayed.
  
  vpn-instance-name refers to the VPN-out.
5. Run network ::0 0
  The default routes to all the Spoke-PEs through MP-BGP are advertised.