ACI - HPE NonStop (Tandem) Configuration

[mbrandon32]

We are in the process of moving our HPE NonStop environments into our ACI fabric and have run into some performance issues. On the NonStop side, they are running a bond interface, with two interfaces in the bond and the bond setting as "balance-alb" aka adaptive load balancing. The issue we are noticing is that ACI is learning the IP of the bond interface from two different MAC addresses. The IP will bounce back and forth between those MACs. When that happens, we are receiving reports of performance degradation. When we disable one of the interfaces from the ACI side, the performance issues disappear. This is similar to configuration option for the bond interface configuration on the NonStop side - specifically configuring the interfaces in an HA, "active-backup" pair.

Has anybody else run into a similar issue with an ACI/NonStop configuration? What was done to correct?

[Robert Burns]

You can disable endpoint learning for that IP. This was added into version 5.x onward. Under the EPG configure a /32 subnet IP with EP learning disabled.

Robert

[mbrandon32]

Thanks Robert. We are currently running version 4.2(6h).

Is this a scenario you've encountered before or is this a Cisco recommended configuration?

[Robert Burns]

Yes we've seen this before with Mainframes and L4-7 devices that share IPs/MACs.  Since you're running 4.2, your best option would be to:

• Add the VIPs in the “L4-L7 Virtual IPs” tab in the EPG. This will disable IP dataplane learning for this IP.
• Enable ARP flooding + GARP based detection in the BD. This will allow endpoint move/learn based on GARP packets

Robert

[mbrandon32]

Thanks Robert. We implemented those configurations but are still running into issues.

My thinking is that the NonStop side will need to update their NIC bond/teaming from balance-alb to either active/backup or 802.3ad for LACP, if possible.

[Robert Burns]

That would be ideal - aggregate the Interfaces on the NonStop and ACI side - this would remove any flapping actions. Some mainframes don't support this, so if Nonstop does, go for it.
Robert