Nexus7000 L2FM-1-L2FM_LINE_FULL_CONDITION impact

[alexander.koeppe]

Dear community,

we're currently in the progress to migrate our N7K Fabricpath network to ACI.

We follow of course the best-practices and connect N7K and ACI with L2out and L3out for migrating physical servers and SVIs in phases.

However, our N7K just recently throwed the following warning message:

%MTM-SLOT4-2-VDC_FE_MAC_TBL_HWM_WARNING: MAC table threshold reached for FE 1. MAC table is 90 percent full 

Although I'm totally aware about the background of this limitations of the F-cards and related warning / error messages, I cannot really do much as I cannot prune VLANs on other Fabricpath links (e.g. VPC Peer-Link).

I'd like to understand the impact when the line_full condition of the link to the L2Out of ACI is hit because too much MACs have been migrated to ACI.

My understanding would be: if no more MACs can be inserted in the MAC table... traffic destined to this MAC is being flooded through the Unkown Unicast Tree and to all CE ports. Multicast might be dropped and can be also flooded by disabling the optimized forwarding for Multicast traffic.

Can somebody confirm my understanding? Does somebody gathered real-life experience of such a situation?

[marce1000]

 - FYI : https://www.cisco.com/c/en/us/support/docs/interfaces-modules/nexus-7000-f2-series-copper-1-10-gigabit-ethernet-module-enhanced/200399-Nexus-7000-F2-F2e-Understanding-and-mit.html

 M.

[alexander.koeppe]

Thanks Marcelo,

However, I already know this document and read it thoroughly. However I coulnd't really find where its explaining the exact impact that happens when a MAC cannot be installed due to lines_full event.

[alexander.koeppe]

I think I know now the impact. It seems we've now hit the line_full condition.

It seems like expected. Anything destined beyond what's already in the MAC table is flooded on all links.

We experience 2Gbps utilization on downlinks where nothing is connected anymore.