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Participant

Newbie - etherchannel

Hi,

I'd like to create an etherchannnel between 2 switches.

The switches are already running and have a gigabit Cat5e link between them (lets say port 25)

Now I want to add port 26 and link it to port 25.

I know the commands etc to configure the etherchannel and for the vlan trunking on it.

Question is:

1. Is there any downtime when creating this? eg will port 25 drop it's connection temporarily?

2. Do I then connect port 26 or is it safe to connect port 26 before the channel is configured?

regards,

Louis

6 REPLIES 6
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Hall of Fame Expert

Newbie - etherchannel

Hi,

If you connect the second port (26) you run the risk of spanning tree issue.  The easiest way to do it is to have a short outage window, shut int 25 connect int 26 and shut it down.  Then add both ports (25 and 26) to the Portchannel and and then issue "no sh" on the Portchannel interface That will bring up all the physical interfaces too.

check with "sh etherchannel summary" to make sure the portchannel has the proper ports and it is up

HTH

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Participant

Newbie - etherchannel

Thanks for the prompt reply and I thought there might have been an issue with having both ports in at the same time.

Can this be done without downtime?

eg

Port 25 is already up, port 26 is not connected.

1. Add port 25 & 26 to new etherchannel so it just runs with port 25

2. Then plug in port 26 to bring etherchannel up to full capacity

regards,

Louis

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Enthusiast

Newbie - etherchannel

Hi,

I think it can be done this way.

Port25 is already connected, let it be. First you configure the etherchannel and all the trunking parameters on both the devices, without physically connecting the port26.

Once your configuration are done. Simply connect the port 26. Then i don't think there raises a STP issue, since you told the device already that they both are single link.

May be there will be downtime for few seconds for the etherchannel to adjust itself with the new port. I guess it would be less than 45 -60 seconds.

Please don't mind if my assumption is wrong. Becuase i'm still a learner.

Please don't forget to rate the posts that are helpful.

Regards,
Chandu

Regards, Chandu
Highlighted
Participant

Newbie - etherchannel

That's the way I'm hoping it can be done.

I have another site where there is already an ethernet channel on 2 gigabit ports (RJ45) and we need to utilise these two for another 2 devices.

There are however 2 gigabit SPF ports that I would like to add to the etherchannel and then remove the 2 RJ45's.

Could this be done without downtime?

Highlighted
Hall of Fame Expert

Newbie - etherchannel

In your first case since you don't already have a portchannel, when you add a port to it, there will sill be short outage to transition to portchannel. Again, you can try this but there is no guarantee how the port and the portchannel can behave at the time and not cause a bigger outage.

In your second case, since you already have a portchannel with copper ports, you can first down the fiber ports, connect them, add them to to the portchannel and than bring the ports up.  Usually best practice for portchannel is to sh the portchannel, add the interfaces and then bring up your portchannel

HTH

Highlighted
Enthusiast

Newbie - etherchannel

When you build the channel the ports will go down and then the respective STP convergence applies, hence losing connectivity.

As said, you need to configure the channel first, if you just plug another link in you will create a loop, and as a result one of the ports will get disabled.

Martin

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