Re: Nexus 5k / 7k Loop

Do you have different domain ID'S on each VPC?
On Aug 24, 2014 6:31 AM, "david bloom" <dbsg13_at_yahoo.com> wrote:

> Hello Everyone,
>
> We have an odd situation that I canb t quite understand - a
> L2 loop is happening.
>
> We have a production 5k environment, and a new 7k lab
> environment.B When I connect the two
> together, the 5kb s immediately report
> a loop and disables learning. B While this happens, traffic in the
> production
> vlan is intermittent, i.e. some pings go though, others dropped.
>
> Both the
> 5kb s and the 7kb s are in a back to back vPC
> configuration.B There is a
> single link
> between 5k04 and 7k02.B At first, we
> set up that single link in a
> port-channel and vPC on both the 7k and 5k.B We then removed the
> port-channel
> and vPC
> config for the link on both sides, and set the link as a standard
> trunk.B B Both scenarios produced the loop b with the
> detection showing on
> the 5k that the same MAC was learned coming from the 7k,
> and on the
> port-channel going to the upstream 5k.
>
> My guess is that this is an
> unsupported config.B We do plan do add a second link from the 7k
> ot the 5k,
> this way we can run back to back vPC between the 7k and 5k.B Ib m thinking
> this will solve the issue.
>
> Question is why would the single link cause a
> loop?
>
> Mac address flooding coming in from the upstream 5k goes through the
> link to the single 7k02. B The flood goes out the port-channel (to both
> downstream 7k03 AND 7k04) and across the vPC peer link, correct? B From
> there,
> each switch (other 7k01, and both downstream 7k03, 7k04) receive the flood
> on
> a vPC port-channel, so it should not flood back, either over the same
> port-channel, or through the downstream vPC peer link?
>
> 5k01 B ---- B 5k02
> B
> B | B B B B \ / B B B |
> 5k03 B ---- B 5k04
> B B B B B B B B B
> B B B |
> B B B B B B B B B B B B |
> 7k01 B ---- 7k02
> B B | B B
> B \ B / B B B |
> 7k03 B --- 7k04
>
> Each horizontal set is a vPC peer, and all
> cross links are
> port-channels in a vPC.B The single
> connection is a standard
> trunk.B The loop
> errors occur on the 5k04 that is connected to the 7k02.
> B 5k03 also reports the errors - the duplicate mac is seen on the vPC
> peer-link from 5k04, and the port-channel to the upstream 5ks.
>
> David
>
>
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Received on Wed Sep 24 2014 - 14:01:44 ART