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Port Channels showing down

I just set up an L2 port channel for testing purposes to a server using two GigE links. Both of the interfaces are showing up/up and passing traffic, and seem to be load-balancing correctly, but the port-channel interface is showing down/down.

The configuration on both of the physical interfaces is:

interface GigabitEthernetx/x/x

switchport mode access

load-interval 30

channel-group 2 mode desirable

spanning-tree portfast

Any ideas on why the Port-Channel interface is showing down/down?

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Accepted Solutions

Re: Port Channels showing down

I doubt whether your Dell servers are able to do PAgP, because it is Cisco proprietary. That would explain why the links are not joining the channel.

There is a possibility that the Dell will do LACP. In that case, you would need "mode active" rather than "mode desirable".

But the surest way to get it to EtherChannel is to force the teaming on the Dell, and to configure the switchports as "mode on".

Once you have done that, could you post a show etherchannel n detail. The "detail" keyword is important. I think you are using channel 2 in your config, and the output you posted shows only channel 1.

Kevin Dorrell

Luxembourg

6 REPLIES
Hall of Fame Super Bronze

Re: Port Channels showing down

Are you looking at port-channel2?

Can we see the output from typing show interface port-channel2

__

Edison.

New Member

Re: Port Channels showing down

what`s the configuration about etherchannel ?

New Member

Re: Port Channels showing down

To clarify further, the configuration on the port channel interface is pretty basic. However, the server that this port channel is going to is a Dell. They specified an Intel program to create a NIC teaming on the server itself. When we use the 802.3AD settings, it does not load-balance correctly. However, when I change the interface over to a PAgP (Cisco proprietary), the links begin to load-balance correctly, but the port-channel interface shows as down.

I think the port-channel interface shows down due to the fact that the interface is trying to negotiate PAgP, but can't because the Intel program on the server is not supporting it.

As for not load-balancing across the two links when using the 802.3ad standard, i'm still not sure.

Purple

Re: Port Channels showing down

To verify the channel is working use the show etherchannel detail command to see if the port channel is actually working . show etherchannel summary will also tell you if the channel is actually working . A lot of times when channeling a server you will have to force the channel on instead of negotiating the channel.

New Member

Re: Port Channels showing down

I changed the GigE interfaces to the 802.3ad standard and the port-channel interface came up. However, I changed it back to PAgP and forced the interface up and it is still showing down/down on the port-channel interface, but the physical interfaces are still up and passing traffic. the show etherchannel summ command shows:

Switch#show ether summ

Flags: D - down P - 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

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 Gi5/0/11(I) Gi5/0/12(I)

Re: Port Channels showing down

I doubt whether your Dell servers are able to do PAgP, because it is Cisco proprietary. That would explain why the links are not joining the channel.

There is a possibility that the Dell will do LACP. In that case, you would need "mode active" rather than "mode desirable".

But the surest way to get it to EtherChannel is to force the teaming on the Dell, and to configure the switchports as "mode on".

Once you have done that, could you post a show etherchannel n detail. The "detail" keyword is important. I think you are using channel 2 in your config, and the output you posted shows only channel 1.

Kevin Dorrell

Luxembourg

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