etherchannel problem

[jean tang]

guys, I have some problems with etherchannel configuration

3 switches(3550/3560): SW1-------SW2--------SW3 (both connecting with each other with two ports, SW3 connects with SW1 also having two ports)

SW1/SW2/SW3: inter range f0/19 -20

                              channel-group 1 mode on

                         inter range f0/21 -22

                              channel-group 1 mode on

I tried on/lacp/pagp mode, but always four ports go down, suspended state (speed,dupluex,native vlan,all same)

It really troubles me

Can I use the same port-channel name 1 for one group in three switches?

Is there too many ports in one group?

any loop occurs?

what am i doing wrong?

thanks a lot

[rtjensen4]

If I understand correctly, you're trying to use group 1 to connect an etherchannel to one switch, and use group 1 to connect a 2nd etherchannel to another switch?

The group number is local to the switch only. But you can't use the same group for different ether channels, the switch will think they're in the same channel.

Switch 1 could have:

Group 1 connecting it to SW2

Group 2 connecting it to SW3

Switch2:

Group 1 Connecting to SW3

Group 2 Connecting to SW1

Switch3:

Group 1 Connecting to SW2

Group 2 Connecting to SW1

[vdadlaney]

Hi Jean,

I will try and attempt an answer to your question. If i understand your scenario correctly it seems you have 3 switches in a the following setup (Hope the ascii comes out correctly)

SW1----------SW2

  \

   \

    \

     \

       SW3

If that is so than you can use channel-group 1 to form the etherchannel between SW1 and SW2. however on SW1 you have to use a different channel-group. If you look at show etherchannel summary with the way you have it configured now you would see that all the ports F0/19 - F0/22 are configured under the same etherchannel which basically means they are going to the same device and this is not correct because you have 2 ports going to SW2 and 2 ports going to SW3. HTH

[jean tang]

rtjensen4 and vdadlaney, thank you for your help

sorry...my english really needs work

actually, the topology is....

SW1----------SW2

  \                 /

   \               / 

    \            /

     \         /

       SW3

but I understand my mistake now~~~~

best regards