H3C Technologies H3C S3600 Series Switches - Manual (Page 245)

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The disadvantage of using static routes is that they cannot adapt to network topology changes. If a fault
or a topology change occurs to the network, the routes may be unreachable and the network may
break.
To avoid such problems, you can configure another route to back up the static route and use the Auto
Detect function to judge the validity of the static route. If the static route is valid, packets are forwarded
according to the static route, and the other route is standby. If the static route is invalid, packets are
forwarded according to the backup route. In this way, the communication is not interrupted, and the
network reliability is improved.
You can bind the static route with a detected group. The Auto Detect function will then detect the group
and judge the validity of the static route according to the returned reachable/unreachable information..
z The static route is valid if the detected group is reachable.
z The static route is invalid if the detected group is unreachable.
You need to create the detected group before performing the following operations.
Follow these steps to configure the auto detect function for a static route:
To do… Use the command… Remarks
Enter system view system-view —
Bind a detected group to
a static route
ip route-static ip-address { mask | mask-length }
{ interface-type interface-number | next-hop }
[ preference preference-value ] [ reject |
blackhole ] detect-group group-number
Required
Auto Detect Implementation in VRRP
Currently, auto detect implementation in VRRP is only supported on S3600-EI series Ethernet switches.
Virtual Router Redundancy Protocol (VRRP) is a fault-tolerant protocol. It assigns a set of switches
acting as gateways to a backup group, which forms a virtual switch. Switches in the backup group elect
a master switch based on priorities to take the responsibility of traffic forwarding. The other switches
operate as backup switches. When the master switch fails, a backup switch takes over to forward traffic,
thus guaranteeing the hosts in the network can communicate with the external network uninterruptedly
through the virtual switch.
However, when the uplink of a switch fails, the backup group cannot sense the uplink failure. If the
uplink of the master switch fails, the hosts in the LAN cannot access the external network, as shown in
Figure 1-1 .