Information Technology Reference
In-Depth Information
To view the channel, do as follows:
Switch-A (enable) show port channel
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
2/1 connected desirable channel WS-C5505 066509957(Sw 2/1
2/2 connected desirable channel WS-C5505 066509957(Sw 2/2
2/3 connected desirable channel WS-C5505 066509957(Sw 2/3
2/4 connected desirable channel WS-C5505 066509957(Sw 2/4
----- ---------- --------- ----------- ------------------------- ----------
Because Switch B was in auto mode, it responded to the PAgP packets and created a channel with Switch
A.
Switch-B (enable)
2000 Jan 14 20:26:41 %PAGP-5-PORTFROMSTP:Port 2/1 left bridg1
2000 Jan 14 20:26:41 %PAGP-5-PORTFROMSTP:Port 2/2 left bridge port 2/2
2000 Jan 14 20:26:41 %PAGP-5-PORTFROMSTP:Port 2/3 left bridge port 2/3
2000 Jan 14 20:26:41 %PAGP-5-PORTFROMSTP:Port 2/4 left bridge port 2/4
2000 Jan 14 20:26:45 %PAGP-5-PORTFROMSTP:Port 2/2 left bridge port 2/2
2000 Jan 14 20:26:45 %PAGP-5-PORTFROMSTP:Port 2/3 left bridge port 2/3
2000 Jan 14 20:26:45 %PAGP-5-PORTFROMSTP:Port 2/4 left bridge port 2/4
2000 Jan 14 20:26:47 %PAGP-5-PORTTOSTP:Port 2/1 joined bridge port 2/1-4
2000 Jan 14 20:26:47 %PAGP-5-PORTTOSTP:Port 2/2 joined bridge port 2/1-4
2000 Jan 14 20:26:47 %PAGP-5-PORTTOSTP:Port 2/3 joined bridge port 2/1-4
2000 Jan 14 20:26:48 %PAGP-5-PORTTOSTP:Port 2/4 joined bridge port 2/1-4
Switch-B (enable) show port channel
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
2/1 connected auto channel WS-C5505 066507453(Sw 2/1
2/2 connected auto channel WS-C5505 066507453(Sw 2/2
2/3 connected auto channel WS-C5505 066507453(Sw 2/3
2/4 connected auto channel WS-C5505 066507453(Sw 2/4
----- ---------- --------- ----------- ------------------------- ----------
It is recommended to set both sides of the channel to desirable so that both sides will try to
initiate the channel in case one side drops out. Setting the EtherChannel ports on Switch B
to desirable mode, even though the channel is currently active and in auto mode, poses no
problem. The command is as follows:
Note
Switch-B (enable) set port channel 2/1-4 desirable
Port(s) 2/1-4 channel mode set to desirable.
Switch-B (enable) show port channel
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
2/1 connected desirable channel WS-C5505 066507453(Sw 2/1
2/2 connected desirable channel WS-C5505 066507453(Sw 2/2
2/3 connected desirable channel WS-C5505 066507453(Sw 2/3
2/4 connected desirable channel WS-C5505 066507453(Sw 2/4
----- ---------- --------- ----------- ------------------------- ----------
Now if Switch A drops out for some reason, or if new hardware replaces Switch A, then Switch B will
try to re-establish the channel. If the new equipment cannot channel, then Switch B will treat its ports
2/1-4 as normal nonchanneling ports. This is one of the benefits of using the desirable mode. If the
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