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Community Member

question about trunking and redundancy for 6509s

I am trying to create redundancy between 6509 and two 3548XLs. I have a 6509 w/ dual sup1a and msfc in one closet and two 3548xl (3548xl-1 and 3548xl-2)switches in another closet. I initially created fiber trunks to each separate 3548xl and it worked fine, but if one fiber link fails, one switch also fails. Is there a way to configure these switches so that there may be one trunk going from 6509 to 3548xl-1 and another trunk going from 6509 to 3548xl-2 while linking the two 3548xls with a gigastack module? Or is there a simpler way to create redundancy between these switches using 2 fiber trunks and/or gigastack modules?

Thanks.

4 REPLIES
Community Member

Re: question about trunking and redundancy for 6509s

Configure 2 fiber trunks going from 6509 to each 3548, the STP will block one of then on each switch for avoid loops, but if the active link fail the block link comes up.

Community Member

Re: question about trunking and redundancy for 6509s

I would run two connections from your 6509 to each of your 3548s. Create a 2gig port-channel from the 6509 to the 3548xl. This way if one of your gig links fail, the port channel will stay up and you will still have a one gig link...and there is no need for a spanning tree recalculation. This is b/c spanning tree treats the port-channel as one logical link. If need be you can then enable trunking (allowing of more than one vlan) over the port-channel. Also, I would use dot1q encapsulation for your trunking.

bc

Community Member

Re: question about trunking and redundancy for 6509s

Why dot1q instead of isl? I'm about to do this between two 6509s.

Community Member

Re: question about trunking and redundancy for 6509s

Two reasons:

1. dot1q is a standard and only tags the frame...isl encapsulates the frame adding bits and making it larger. it doesn't make it that much larger but the less bits the better right?

2. we have an ans contract with cisco. they are very specific with what they recommend. dot1q is something that they seem to harp on! why i do not know but i'll take the advice.

bc

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