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9/23
2014
Carole Warner Reece

Troubleshooting Port-Channels and Trunks Between HP-UX Servers and Nexus Switches

One of my customers asked for helping troubleshooting a port-channel between a HP-UX server and a Cisco Nexus 7000. I did not know much about HP-UX server configuration, but I agreed to take a look at it.
Key take-away: Server terminology does not always match networking terminology.

Background

My customer told me that they wanted to configure network redundancy from the HP RX2800i4 server running HP-UX to one of their core switches (Nexus7Ks). They were told that the HP-UX system runs software to provide port aggregation (APA) that is supposed to be compatible with “most” switch vendors.  However, they were not able to successfully configure the port-channel between the server and their 7K.

    Note: This is not a vPC configuration.

I believe that both Cisco and HP support folks were trying to resolve the problem previously, but the issue was still lingering when I got the call.

I suggested that my customer check that the LACP mode on both sides was set to active — on the HP-UX Link Aggregate this is LACP_AUTO, on the Nexus switch it is channel-group channel-number mode active for the interfaces in the port-channel.

She let me know that on one of the last tests, the port-channel came up, and it was set to active. So the problem had evolved, she believed the port-channel was working.

I think she said that the server guy had configured an IP address on the trunk. This was a bit confusing to me – I asked if it was a Layer 3 port channel. She said no, but was not sure how or where the IP address was configured.

She did know that when the port-channel was up there was no IP accessibility across the port-channel to other network resources. The HP server could only ping itself.

Troubleshooting

I then got to review the Nexus configuration over a webex session. It looked fine to me – two VLANs were allowed across the port-channel, and it was configured as a Layer 2 trunk. The port-channel was down with suspended interfaces, but the HP server ports had been removed from the port-channel during a previous troubleshooting session.

We did not have access to the server initially, so I reviewed the HP documents for HP-UX Port aggregation (APA) and for configuring VLANs on HP-UX. What I found interesting:

“HP Auto Port Aggregation (APA) is a software product that creates link aggregates, often called trunks, which provide a logical grouping of two or more physical ports into a single fat pipe.”

This seemed to be one of th