Etherchannel Question

Hey guys. I have a question regarding etherchannel. It seems when using both PAgP and LACP, as soon as I force the ports of the channel to be 1000/Full, the channel won't form. It works perfectly with auto/auto.

Here's the config and show etherchannel summary for both switches.

Switch 1:

DSW1_CiscoLab#sh run int po1
Building configuration...

Current configuration : 31 bytes
!
interface Port-channel1
end

DSW1_CiscoLab#sh run int gi0/1
Building configuration...

Current configuration : 102 bytes
!
interface GigabitEthernet0/1
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/2
Building configuration...

Current configuration : 102 bytes
!
interface GigabitEthernet0/2
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/3
Building configuration...

Current configuration : 102 bytes
!
interface GigabitEthernet0/3
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/4
Building configuration...

Current configuration : 102 bytes
!
interface GigabitEthernet0/4
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh etherchannel sum
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Gi0/1(P)    Gi0/2(P)    Gi0/3(P)    
                                 Gi0/4(P)

Switch 2:

DSW2_CiscoLab#sh run int po1
Building configuration...

Current configuration : 66 bytes
!
interface Port-channel1
 switchport mode dynamic desirable
end

DSW2_CiscoLab#sh run int gi0/1
Building configuration...

Current configuration : 137 bytes
!
interface GigabitEthernet0/1
 switchport mode dynamic desirable
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/2
Building configuration...

Current configuration : 137 bytes
!
interface GigabitEthernet0/2
 switchport mode dynamic desirable
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/3
Building configuration...

Current configuration : 137 bytes
!
interface GigabitEthernet0/3
 switchport mode dynamic desirable
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/4
Building configuration...

Current configuration : 137 bytes
!
interface GigabitEthernet0/4
 switchport mode dynamic desirable
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh etherchannel summary
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Gi0/1(P)    Gi0/2(P)    Gi0/3(P)    
                                 Gi0/4(P)

When I add the following, the channel goes down and doesn't come back up.

Switch 1:

DSW1_CiscoLab#sh run int po1
Building configuration...

Current configuration : 56 bytes
!
interface Port-channel1
 speed 1000
 duplex full
end

DSW1_CiscoLab#show etherchannel sum
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Gi0/1(D)    Gi0/2(D)    Gi0/3(D)    
                                 Gi0/4(D)

Switch 2:

DSW2_CiscoLab#sh run int po1
Building configuration...

Current configuration : 91 bytes
!
interface Port-channel1
 switchport mode dynamic desirable
 speed 1000
 duplex full
end

DSW2_CiscoLab#sh etherchannel sum
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SD)         PAgP      Gi0/1(D)    Gi0/2(D)    Gi0/3(D)    
                                 Gi0/4(D)

As I understand it, both sides have to match on speed/duplex (among other things). In this case, they match but still won't form a channel.

Both switches are Catalyst 2960Gs running the same version of IOS.

What am I missing?

Thanks.

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Comments

networker050184

I believe you need the speed/duplex to match on the physical interfaces and the port-channel.

iproute

Thanks for the reply. By applying the commands to the port channel interface, it applies them to the member interfaces as well.

Switch 1:

DSW1_CiscoLab#sh run int po1
Building configuration...

Current configuration : 56 bytes
!
interface Port-channel1
 speed 1000
 duplex full
end

DSW1_CiscoLab#sh run int gi0/1
Building configuration...

Current configuration : 127 bytes
!
interface GigabitEthernet0/1
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/2
Building configuration...

Current configuration : 127 bytes
!
interface GigabitEthernet0/2
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/3
Building configuration...

Current configuration : 127 bytes
!
interface GigabitEthernet0/3
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW1_CiscoLab#sh run int gi0/4
Building configuration...

Current configuration : 127 bytes
!
interface GigabitEthernet0/4
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

Switch 2:

DSW2_CiscoLab#sh run int po1  
Building configuration...

Current configuration : 91 bytes
!
interface Port-channel1
 switchport mode dynamic desirable
 speed 1000
 duplex full
end

DSW2_CiscoLab#sh run int gi0/1
Building configuration...

Current configuration : 162 bytes
!
interface GigabitEthernet0/1
 switchport mode dynamic desirable
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/2
Building configuration...

Current configuration : 162 bytes
!
interface GigabitEthernet0/2
 switchport mode dynamic desirable
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/3
Building configuration...

Current configuration : 162 bytes
!
interface GigabitEthernet0/3
 switchport mode dynamic desirable
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

DSW2_CiscoLab#sh run int gi0/4
Building configuration...

Current configuration : 162 bytes
!
interface GigabitEthernet0/4
 switchport mode dynamic desirable
 speed 1000
 duplex full
 channel-protocol pagp
 channel-group 1 mode desirable non-silent
end

networker050184

Do the ports come up when not in the etherchannel? Any messages in the log? Have you tried bouncing the etherchannel after changing both sides?

creamy_stew

Interesting, I'm looking to implement etherchannel in a production environment. This scares me

Have you looked for err-disabled ports? Especially due to etherchannel misconfig.

edit: this is probably not an etherchannel issue. I now remember I had a problem adding an additional 2960G. I would get some sort of VTP error logs (all switches running transparent) When I switched to auto, the logs went away. Not really a problem, except ALL the other switches were hard set to 1000/full.

mikej412

What kind of cable are you using? Auto-MDIX is disabled when you manually set the speed or duplex -- so if it's copper and straight through that could be an issue.

Checking for err-disable is another good idea. If you changed the config while the ports were no shut, you may not have been fast enough making the configuration changes on both sides.

iproute

mikej412 wrote: »

What kind of cable are you using? Auto-MDIX is disabled when you manually set the speed or duplex -- so if it's copper and straight through that could be an issue.

Hey all - been away for a few. This is the most likely cause. I'm using straight through cables relying on auto MDIX (basically, I have to make cross-overs if I want them). I'll try some crossover cables and check this tomorrow (my lab is at work, I am at home).

Thanks for all the responses.

iproute

Confirmed. With a cross over cable, the port comes right up (I tried it only with one as I don't see a need to make 4 cross over cables for this test

DSW1_CiscoLab#sh etherchannel summary
Flags:  D - down        P - bundled in port-channel
        I - stand-alone s - suspended
        H - Hot-standby (LACP only)
        R - Layer3      S - Layer2
        U - in use      f - failed to allocate aggregator

        M - not in use, minimum links not met
        u - unsuitable for bundling
        w - waiting to be aggregated
        d - default port


Number of channel-groups in use: 1
Number of aggregators:           1

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-----------------------------------------------
1      Po1(SU)         PAgP      Gi0/1(P)    Gi0/2(D)    Gi0/3(D)    
                                 Gi0/4(D)    

DSW1_CiscoLab#

Thanks Mike for this valuable nugget of info.

Thanks for all the replies.

chrisone

creamy_stew wrote: »

Interesting, I'm looking to implement etherchannel in a production environment. This scares me

Shouldn't be a problem even if you brought down the switch, as long as you don't implement it during business hours. Ask for a scheduled downtime "network maintenance" and you should be solid to work free of stress.