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Configuring BGP FRR
When a link fails, the packets on the link are discarded, and a routing loop might occur until BGP
completes routing convergence based on the new network topology.
You can enable BGP fast reroute (FRR) to resolve this issue.
Figure 64 Network diagram for BGP FRR
After you configure FRR on Router B as shown in Figure 64, BGP generates a backup next hop
Router C for the primary route. BGP uses ARP (for IPv4), echo-mode BFD (for IPv4), or ND (for IPv6)
to detect the connectivity to Router D. When the link to Router D fails, BGP directs packets to the
backup next hop. At the same time, BGP calculates a new optimal route, and forwards packets over
the optimal route.
You can use the following methods to configure BGP FRR:
• Method 1—Execute the pic command in BGP address family view. BGP calculates a backup
next hop for each BGP route in the address family if there are two or more unequal-cost routes
that reach the destination.
• Method 2—Execute the fast-reroute route-policy command to use a routing policy in which a
backup next hop is specified by using the command apply [ ipv6 ] fast-reroute
backup-nexthop. The backup next hop calculated by BGP must be the same as the specified
backup next hop. Otherwise, BGP does not generate a backup next hop for the primary route.
You can also configure if-match clauses in the routing policy to identify the routes protected by
FRR.
If both methods are configured, Method 2 takes precedence over Method 1.
BGP supports FRR for IPv4 and IPv6 unicast routes, but not for IPv4 and IPv6 multicast routes.
To configure BGP FRR (IPv4 unicast address family):
1. Enter system view.
N/A
2. Configure the source
address of echo packets.
bfd echo-source-ip
ipv4-address
By default, no source address is
specified for echo packets.
This step is required when
echo-mode BFD is used to
detect the connectivity to the
next hop of the primary route.
Specify a source IP address that
does not belong to any local
network.
For more information about this
command, see High Availability
Command Reference.
3. Create a routing policy and
enter routing policy view.
route-policy
route-policy-name
node-number
By default, no routing policies
exist.
Backup nexthop: Router C
Router ENexthop: Router D
Router A Router B
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