NIC card addresses

[Carey Goad]

I need to install a secondary NIC card on my HP-UX v11 L-class box. The subnet mask is 255.255.0.0. I have two IP addresses: 10.100.1.136 and 10.100.1.191. Will this work - configuring these addresses into each NIC? If I try this (SAM let me do it), will I run into problems?

Thanks (in advance),
Carey

[Iris Berr]

Hello Carey,

this should not be a problem.
SAM will make you the entrys for each NIC in the /etc/rc.config.d/netconf.
You can check this with the "netstat -i" command.

regards
Iris

[Andreas Voss · Accepted solution]

Hi,

yes you can but do not connect both NIC's to one physical network because the two ip addresse are at the same logical network and the system can have trouble in sending packets.

Regards

[Lasse Knudsen]

Hi Carey,

What are your reasons for doing this. As Andreas is mentioning you are going to give yourself some problems as far as sending packets are concerned. What happens is that packets are only sent from one interface because they are on the same logical network.

If you want your machine to have 2 IP-adresses attached to the same network you should use "aliasing" instead.

You can just do "ifconfig lan0:1 10.100.1.191 netmask 255.255.0.0" it will do the same.

It seems like SAM will handle this using "Add IP logical Interface" (I do not know if it works - never had 100% confidence in SAM)

[Carey Goad]

I am trying to do this because our Networking folks said our NIC card may be maxed out. We are experiencing some slow connection times (mostly for remote users) and this was an attempt to fix that. I only have one network here to connect to (10.100.x.x)... .

It looks like maybe the "aliasing" thing is what I need - I definetly do not want problems as this is a production box. Any help on that?

Thanks,
Carey

[Lasse Knudsen]

Carey,

The problem is that when you attach both NIC's to the same IP-net using 2 addresses it might not load-balance.

Imagine that you want to send a packet to eg. 10.100.100.100. Then the application will send this through the protocol stack but It will always go out through the one NIC since the shortest path (routing-wise) are the same on the 2 NICS. I'm not certain if this is the same for both UDP & TCP based apps. The bottomline here that you need to know *exactly* how things behave before you can gain anything from adding a second NIC.

If you are looking for more bandwith then I suggest you go for a higher bandwith NIC (are you using GigaBit ??) or look into trunking/channeling/bundling - Dont know how this is done in HP-UX - others ??

Btw. "aliasing" will not help you in this case - so do not go for that.

[Craig Gilmore]

You probably want to look at Auto Port Aggregation. This is the "bundling" or "trunking" software that HP offers in conjunction with routers or switches that support Port Aggregation.

If you are seeing slow or long response times for network connections both locally and remotely, then you might have a bandwidth or latency problem. However if it is just the remote users that see the slow response, it is probably link speed rather than a bandwidth problem.

Port Aggregation takes multiple (up to 4) LAN interfaces and builds 1 logical interface from the multiple connection points. This would only use 1 IP address and solves the routing and connection problems previously mentioned.

It doesn't sound like the problem you are experiencing is a bandwidth issue, but it is hard to tell without using a sniffer/analyzer to look at the environment.