Re: Nexus 5k / 7k Loop

Hi David

What codes were you running on the 5k and 7k's be a good one to search back on...

--
BR
Tony
Sent from my iPad
> On 22 Aug 2014, at 02:18, david bloom <dbsg13_at_yahoo.com> wrote:
> 
> In case anyone else has this issue - TAC has identified that this can actually
> happen within the 77xx platforms and is a rare but known bug. B They have seen
> this before, but are unsure of a root cause. B Either the L2FM or the port
> index manager was not properly adding links to the vPC port-channel, and a L2
> loop formed. B The fix can be as simple as a system reload, or in some cases
> just flapping the links.
> 
> 
> ________________________________
> From: david bloom
> <dbsg13_at_yahoo.com>
> To: Cisco Certification <ccielab_at_groupstudy.com> 
> Sent:
> Tuesday, August 19, 2014 10:58 AM
> Subject: Re: Nexus 5k / 7k Loop
> 
> 
> 
> As an
> update - we just completed the 2nd uplink from the 5k to the 7k, created
> port-channels and back to back vPC, however the loop still exists...
> ________________________________
> From: david bloom <dbsg13_at_yahoo.com>
> To:
> Cisco Certification <ccielab_at_groupstudy.com> 
> Sent: Tuesday, August 19, 2014
> 9:38 AM
> Subject: Nexus 5k / 7k Loop
> 
> 
> 
> Hello Everyone,
> 
> We have an odd
> situation that I canbt 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 5kbs 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 5kbs and the 7kbs 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  Ibm 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
> 
> 
> Blogs and organic groups at http://www.ccie.net
> 
> _______________________________________________________________________
> Subscription information may be found at: 
> http://www.groupstudy.com/list/CCIELab.html
Blogs and organic groups at http://www.ccie.net