How Monitor Link Works - 3Com 5500-EI PWR Install Manual

How Monitor Link Works

Figure 2-2 Network diagram for a monitor link group implementation
Eth1/0/11
Switch C
Eth1/0/1
Eth1/0/2
Eth1/0/3
Eth1/0/1
Eth1/0/2
Switch A
As shown in Figure
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.
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.
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.
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.
Eth1/0/12
Switch E
Switch D
Eth1/0/1
Eth1/0/2
BLOCK
Switch B
2-2, the devices Switch C and Switch D are connected to the uplink device Switch E.
2-2