Controlling Advertisement of Address Pool UNRs

If BRASs work in load balancing mode, the BRASs must be configured to control advertisement of UNRs of configured address pools.

In a dual-system hot backup scenario, BRASs control the advertisement of UNRs of configured address pools in either of the following modes:

Manual control: If two BRASs work in load balancing mode, each BRAS is configured with two address pools. One is the primary address pool and the other is the secondary address pool. The primary address pool on one BRAS is the secondary address pool on the other BRAS. The cost value of the primary address pool must be less than that of the secondary address pool on the same BRAS, allowing the primary address pool to be preferentially used. The cost values can be set in a routing policy, which allows the UNR of the primary address pool to have higher route precedence than that of the secondary address pool. For details about how to configure a routing policy, see Configuring a Routing Policy in HUAWEI NetEngine 8000 F Series Router Configuration Guide - IP Routing.
Automatic control: This mode can be more easily deployed than manual control. Automatic control prevents the problem where UNRs cannot be advertised in time after a master/backup BRAS switchover is triggered by a BRAS fault and then the fault is rectified. The default route cost can be used to control route preference. If dual-system hot backup is configured on BRASs, a routing protocol imports UNRs and trusts UNR preference values. This allows the network segment route of the primary address pool to have higher route precedence than that of the secondary address pool.

Run system-view
The system view is displayed.
Run peer-backup route-cost auto-advertising
The BRAS is configured to use the default route cost to control route preference during route generation. The route can be an address pool UNR or a route to a loopback interface of the LAC on an L2TP tunnel.

Address pool UNRs are not updated in real time no matter whether the BRAS is configured to use the default route cost to control route preference. Route control takes effect only when the address pool is re-bound to the RBS.
Run commit
The configuration is committed.

To use a routing policy to allow the UNR of the primary address pool to have the highest preference, perform any of the following operations:

Run the import-route unr route-policy route-policy-name command in the IS-IS view.
Run the import-route unr route-policy route-policy-name command in the OSPF view.
Run the import-route unr route-policy route-policy-name command in the BGP view.

To reserve the cost values of UNRs imported by a routing protocol, perform any of the following operations based on the type of the routing protocol:

Run the import-route unr inherit-cost command in the IS-IS view.
Run either of the following commands in the OSPF view:
1. default cost inherit-metric
2. import-route unr
Run the import-route unr command in the BGP view.