How does HPUX handle multiple NICS when one is an APA

[PCD_HPUX Group]

I am about to test HP Auto Port Aggregation on a development server running HP-UX 11i V2. The NIC that is currently used as the primary interface and has the address recorded in dns, will not be included in the ports to be aggregated. I will use 4 other ports in the aggregate which will use an ip address on a different subnet than the subnet of the primary NIC. The idea is to be able to bring the aggregate up and down for testing without impacting the other development work on the server. The question is, will shutting down the aggregate affect connections made to the primary NIC? I don't think inbound data for connections to the primary NIC will be affected, but how does HP-UX handle out bound data for connections made using the primary NIC? If HP-UX decides that the APA aggregate is the shortest path to the outbound destination, will it use the APA aggregate to send its data? Would HP-UX handle outbound traffic differently if the APA was a single NIC in this situation? Does HP-UX 11i V3 behave differently in this situation than 11i V2?

[Tim Nelson]

Unless you use an IP/subnet on the aggregate and change or create some different routes then nothing will be effected.

Certainly if you assign a subnet that duplicates something else, somewhere else in your network then yes there will be issues.

Pick something unused and do not change any routes.

10.20.30.x
10.1.1.x
10.100.55.x

[Steven E. Protter]

Shalom,

As far as I know just fine, just make sure the APA NIC(s) and the non APA NIC card are not on the same network.

SEP

[PCD_HPUX Group]

Thanks for the replies. The primary NIC and APA will be on different subnets. There will be no routes except the default route which will point to the router on the primary NIC's subnet. When a connection is made to the primary NIC, do all inbound and outbound packets flow through the primary NIC? Are there situations where packets might flow through the APA interface? If packets flow through the APA interface, will shutting down the APA interface disrupt the connection or just force the packets to be retransmitted out of the primary NIC?

[rick jones · Accepted solution]

WRT this question there is nothing special about an APA aggregate - IP and above will treat an aggregate just the same as any other interface.

That said, unless you do something with the routing to suggest that the aggregate is the path to use for traffic that would have otherwise flowed over the primary interface, the aggregate's going up and down should have no effect on anything happening on the primary.

[PCD_HPUX Group]

Thanks for the reply and the help clearing my uncertainty. I will be closing this thread now that I can comfortably provide the developers with assurances that the testing should have no impact on their activities.

[PCD_HPUX Group]

The replies provided and walking through a couple "what if" scenarios with support has convinced me I can re-assure the developers that the testing will not impact their activities.