2-2
How Monitor Link Works
Figure 2-2 Network diagram for a monitor link group implementation
BLOCK
Switch A Switch B
Eth1/0/1
Eth1/0/2
Switch C Switch D
Switch E
Eth1/0/1
Eth1/0/2
Eth1/0/3
Eth1/0/1
Eth1/0/2
Eth1/0/11
Eth1/0/12
As shown in
Figure 2-2, the devices Switch C and Switch D are connected to the uplink device Switch E.
Switch C is configured with a monitor link group, where Ethernet 1/0/1 is the uplink port, while Ethernet
1/0/2 and Ethernet 1/0/3 are the downlink ports. Switch A is configured with a smart link group, where
Ethernet 1/0/1 is the master port and Ethernet 1/0/2 is the slave port.
z If Switch C is not configured with monitor link group, when the link for the uplink port Ethernet 1/0/1
on Switch C fails, the links in the smart link group are not switched because the link for the master
port Ethernet 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 Ethernet 1/0/1.
z If Switch C is configured with monitor link group and monitor link group detects that the link for the
uplink port Ethernet 1/0/1 fails, all the downlink ports in the group are shut down; therefore,
Ethernet 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 Ethernet 1/0/1. Then, Smart Link immediately activates the
slave port Ethernet 1/0/2 so that traffic is switched to the backup link.
z Currently, member ports of a monitor link group cannot be dynamic link aggregation groups.
z 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.
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