H3C Technologies H3C S5560 Series Switches - Manual (Page 278)

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To enable BFD for a BGP peer (IPv6):
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter BGP view or BGP-VPN
instance view.
• Enter BGP view:
bgp as-number
• Enter BGP-VPN instance view:
a. bgp as-number
b. ip vpn-instance vpn-instance-name
N/A
3. Enable BFD to detect the link to the
specified IPv6 BGP peer.
peer ipv6-address [ prefix-length ] bfd
[ multi-hop | single-hop ] By default, BFD is
not enabled.
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 61 Network diagram for BGP FRR
After you configure FRR on Router B as shown in Figure 61 , BGP generates a backup next hop Router C
for the primary route. BGP uses ARP, 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 after route selection.
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 a BGP route in the address family if there are two or more unequal-cost routes that reaches
the destination.
• Method 2—Execute the fast-reroute route-policy command to reference a routing policy in which a
backup next hop is specified by using the apply [ ipv6 ] fast-reroute backup-nexthop command.
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):
Backup nexthop: Router C
Router E Nexthop: Router D Router A Router B