HP 6125XLG - Page 262

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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 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.
There are two 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 to reach 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 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):
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Configure the source address
of echo packets.
bfd echo-source-ip ip-address
By default, no source address is
specified for echo packets.
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
permit node node-number
By default, no routing policy is created.
For more information about this
command, see Layer 3—IP Routing
Command Reference.
4. Set the backup next hop for
FRR.
apply fast-reroute
backup-nexthop ip-address
By default, no backup next hop is set.
For more information about this
command, see Layer 3—IP Routing
Command Reference.
5. Return to system view.
quit N/A
Backup nexthop: Router C
Router ENexthop: Router D
Router A Router B