topic Re: multiple IPs same NIC same subnet advisable? in Operating System - HP-UX

multiple IPs same NIC same subnet advisable?

Mike Patterson — Mon, 10 Jan 2011 19:54:32 GMT

We've built 3 HP-UX 11.31 systems on 3 BL860c blades for our Oracle DBAs who have installed Oracle 11g RAC there.

Each blade has 4 onboard NICs (we'll add a mezzanine card later to add APA).

Per our Architect's specs, on each blade, we have:
IP 1 in 192.168.204.x subnet on lan0.
IP 2 in 10.xx.xx.xx subnet on lan1
IP 3 in 192.168.75.xx subnet on lan2
IP 4 in 192.168.75.xx subnet on lan2:801
(this last "VIP" floating IP is automatically configured by Oracle RAC)
No IP on lan3

Problem symptom: we have seen packet loss pinging IP3 on one system from another RAC node and IP4 (VIP floater) transferring to another node intermittently.

Basic question: is it advisable to allow Oracle to configure IP 4 on 192.178.75.xx network on lan2:801 in the same subnet as IP 3?

Re: multiple IPs same NIC same subnet advisable?

Alzhy — Mon, 10 Jan 2011 20:20:39 GMT

"Basic question: is it advisable to allow Oracle to configure IP 4 on 192.178.75.xx network on lan2:801 in the same subnet as IP 3? "

I don't think you can even assign a different LAN / network address to a VIP than its non-VIP physical's IP.

So yes.

Check your netmasks though.

Re: multiple IPs same NIC same subnet advisable?

Mel Burslan — Mon, 10 Jan 2011 23:25:14 GMT

Just to correct Alzhy's misconception, you *can* configure the interface to a different subnet if your network infrastructure and networks admins do their portion of the task properly. Most modern blade servers if not all, support what-so-called VLAN trunking or VLAN Tagging, which enables running more than one network on any given physical interface. But is is no longer straight forward. One needs to work hand in hand with the network infrastructure people as the configuration is anything but trivial.

So, short answer, anything is possible but proceed with extreme caution.

Re: multiple IPs same NIC same subnet advisable?

Alzhy — Tue, 11 Jan 2011 13:04:36 GMT

Mel,

I am just folowings what our venerable Network Team told us.

So ye saying that if lan900 is 10.10.10.100, I can have lan900:1 as 192.168.10.100 ?

Yours truly.

Re: multiple IPs same NIC same subnet advisable?

Doug O'Leary — Tue, 11 Jan 2011 13:42:52 GMT

Hey;

>>So ye saying that if lan900 is 10.10.10.100, I can have lan900:1 as 192.168.10.100 ?

No; that you can't have. The multiplexed IPs have to be on the same subnet as the initial one assigned to the card.

Doug

Re: multiple IPs same NIC same subnet advisable?

Alzhy — Tue, 11 Jan 2011 13:46:32 GMT

That is what I thought too doug.. thanks.

Well Mell?

Re: multiple IPs same NIC same subnet advisable?

rick jones — Tue, 11 Jan 2011 18:05:52 GMT

One most certainly can configure multiple IPs, in different IP subnets on top of the same physical NIC. Heck, one can even configure multiple physical NICs with IPs in the same IP subnet, although it does lead to complications in getting traffic flowing where one may normally expect it to flow. (perhaps necessitating static route entries and/or manipulation of the ip_strong_es_model setting in ndd)