Creating Etherchannel group on live network

Discussion in 'Cisco' started by dcox@wcgh.org, Oct 31, 2007.

  1. Guest

    I have been playing with Cisco switches and VLANs for a while and have
    learned alot by trial and error.

    I have a situation that I'd like a little more info before I proceed.

    I have 2 2960G switches that connect my server room to a wire closet.

    I'd like to create an etherchannel between the 2 for increased
    bandwidth and redundancy.

    I have a good idea of the commands involved but I need to know if
    there will be any network interruption while I am creating the
    etherchannel group on the 2 switches.
    I'm not sure either if I can make the physical connections on the
    additional ports without causing a loop problem.
    This is a live network for a 24/7 business. I can schedule downtime
    but I'd rather not if i don't have to.

    Any info or advive would be welcome.

    dc
    , Oct 31, 2007
    #1
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  2. Trendkill Guest

    On Oct 31, 10:07 am, wrote:
    > I have been playing with Cisco switches and VLANs for a while and have
    > learned alot by trial and error.
    >
    > I have a situation that I'd like a little more info before I proceed.
    >
    > I have 2 2960G switches that connect my server room to a wire closet.
    >
    > I'd like to create an etherchannel between the 2 for increased
    > bandwidth and redundancy.
    >
    > I have a good idea of the commands involved but I need to know if
    > there will be any network interruption while I am creating the
    > etherchannel group on the 2 switches.
    > I'm not sure either if I can make the physical connections on the
    > additional ports without causing a loop problem.
    > This is a live network for a 24/7 business. I can schedule downtime
    > but I'd rather not if i don't have to.
    >
    > Any info or advive would be welcome.
    >
    > dc


    I can't recall exactly, but I think if you keep the additional ports
    shutdown, configure the trunks, configure the virtual port channels
    and add the interfaces, and then 'no shut' the interfaces, you should
    be ok. If you turn up the trunk first, spanning-tree will need to run
    and it could take down your active link, especially if it is a non-
    preferred path.

    While I think this will work without outage, I would never recommend
    messing with trunks and not scheduling and outage. Spanning tree is a
    nasty beast, and without knowing your whole network design, nothing
    can be promised.

    I guess if these aren't trunks and are simple access ports with
    crossovers (no trunks), then you could do the above with portfast, but
    again need to be VERY careful here.
    Trendkill, Oct 31, 2007
    #2
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  3. Guest

    On 31 Oct, 14:28, Trendkill <> wrote:
    > On Oct 31, 10:07 am, wrote:
    >
    >
    >
    >
    >
    > > I have been playing with Cisco switches and VLANs for a while and have
    > > learned alot by trial and error.

    >
    > > I have a situation that I'd like a little more info before I proceed.

    >
    > > I have 2 2960G switches that connect my server room to a wire closet.

    >
    > > I'd like to create an etherchannel between the 2 for increased
    > > bandwidth and redundancy.

    >
    > > I have a good idea of the commands involved but I need to know if
    > > there will be any network interruption while I am creating the
    > > etherchannel group on the 2 switches.
    > > I'm not sure either if I can make the physical connections on the
    > > additional ports without causing a loop problem.
    > > This is a live network for a 24/7 business. I can schedule downtime
    > > but I'd rather not if i don't have to.

    >
    > > Any info or advive would be welcome.

    >
    > > dc

    >
    > I can't recall exactly, but I think if you keep the additional ports
    > shutdown, configure the trunks, configure the virtual port channels
    > and add the interfaces, and then 'no shut' the interfaces, you should
    > be ok. If you turn up the trunk first, spanning-tree will need to run
    > and it could take down your active link, especially if it is a non-
    > preferred path.
    >
    > While I think this will work without outage, I would never recommend
    > messing with trunks and not scheduling and outage. Spanning tree is a
    > nasty beast, and without knowing your whole network design, nothing
    > can be promised.
    >
    > I guess if these aren't trunks and are simple access ports with
    > crossovers (no trunks), then you could do the above with portfast, but
    > again need to be VERY careful here.- Hide quoted text -


    As mentioned it's not really the way to have a long
    and happy life however I have the idea that this might work.
    I am not at all sure.

    Use 2 new ports for the channel on each end.
    Configure it all up (shutdown).

    Configure STP costs such that the existing link is preferred.
    Note that you will have to do this for *all* vlans that cross
    the port channel.

    Bring up the new links.

    If the channel works you may not end up with a loop:)

    To transfer the traffic to the new links change the costs
    on them such that they are lower than the existing link.
    I think that the fail over should lose few packets. Maybe a one
    second outage.
    , Oct 31, 2007
    #3
  4. Trendkill Guest

    On Oct 31, 4:24 pm, wrote:
    > On 31 Oct, 14:28, Trendkill <> wrote:
    >
    >
    >
    > > On Oct 31, 10:07 am, wrote:

    >
    > > > I have been playing with Cisco switches and VLANs for a while and have
    > > > learned alot by trial and error.

    >
    > > > I have a situation that I'd like a little more info before I proceed.

    >
    > > > I have 2 2960G switches that connect my server room to a wire closet.

    >
    > > > I'd like to create an etherchannel between the 2 for increased
    > > > bandwidth and redundancy.

    >
    > > > I have a good idea of the commands involved but I need to know if
    > > > there will be any network interruption while I am creating the
    > > > etherchannel group on the 2 switches.
    > > > I'm not sure either if I can make the physical connections on the
    > > > additional ports without causing a loop problem.
    > > > This is a live network for a 24/7 business. I can schedule downtime
    > > > but I'd rather not if i don't have to.

    >
    > > > Any info or advive would be welcome.

    >
    > > > dc

    >
    > > I can't recall exactly, but I think if you keep the additional ports
    > > shutdown, configure the trunks, configure the virtual port channels
    > > and add the interfaces, and then 'no shut' the interfaces, you should
    > > be ok. If you turn up the trunk first, spanning-tree will need to run
    > > and it could take down your active link, especially if it is a non-
    > > preferred path.

    >
    > > While I think this will work without outage, I would never recommend
    > > messing with trunks and not scheduling and outage. Spanning tree is a
    > > nasty beast, and without knowing your whole network design, nothing
    > > can be promised.

    >
    > > I guess if these aren't trunks and are simple access ports with
    > > crossovers (no trunks), then you could do the above with portfast, but
    > > again need to be VERY careful here.- Hide quoted text -

    >
    > As mentioned it's not really the way to have a long
    > and happy life however I have the idea that this might work.
    > I am not at all sure.
    >
    > Use 2 new ports for the channel on each end.
    > Configure it all up (shutdown).
    >
    > Configure STP costs such that the existing link is preferred.
    > Note that you will have to do this for *all* vlans that cross
    > the port channel.
    >
    > Bring up the new links.
    >
    > If the channel works you may not end up with a loop:)
    >
    > To transfer the traffic to the new links change the costs
    > on them such that they are lower than the existing link.
    > I think that the fail over should lose few packets. Maybe a one
    > second outage.


    Yeah that is why I said turn up the new configuration on a single port
    that you are going to channel with the existing, to hopefully avoid
    spanning tree having to run. I believe if the channel is pre-
    configured, and you simply bring up the second port, it will treat it
    as a down link in an etherchannel and simply add it back into the
    channel. You'd probably want to lab this first though.
    Trendkill, Nov 1, 2007
    #4
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