How Monitor Link Works - H3C S5100-SI Operation Manual

How Monitor Link Works

Figure 2-2 Network diagram for a monitor link group implementation
As shown in Figure
Switch C is configured with a monitor link group, where GigabitEthernet 1/0/1 is the uplink port, while
GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 are the downlink ports. Switch A is configured with a
smart link group, where GigabitEthernet 1/0/1 is the master port and GigabitEthernet 1/0/2 is the slave
port.
If Switch C is not configured with monitor link group, when the link for the uplink port
GigabitEthernet 1/0/1 on Switch C fails, the links in the smart link group are not switched because
the link for the master port GigabitEthernet 1/0/1 of Switch A configured with smart link group
operates normally. Actually, however, the traffic on Switch A cannot be up-linked to Switch E
through the link of GigabitEthernet 1/0/1.
If Switch C is configured with monitor link group and monitor link group detects that the link for the
uplink port GigabitEthernet 1/0/1 fails, all the downlink ports in the group are shut down; therefore,
GigabitEthernet 1/0/3 on Switch C is blocked. Now, smart link group configured on Switch A
detects that a link fault occurs on the master port GigabitEthernet 1/0/1. Then, Smart Link
immediately activates the slave port GigabitEthernet 1/0/2 so that traffic is switched to the backup
link.
Currently, member ports of a monitor link group cannot be dynamic link aggregation groups.
If the uplink or downlink port in the monitor link group is a link aggregation group, you cannot
directly delete this aggregation group or change this aggregation group into a dynamic aggregation
group. To delete this aggregation group, you must first unbind this aggregation group from the
Monitor Link.
2-2, the devices Switch C and Switch D are connected to the uplink device Switch E.
2-2