topic Re: Multiple NIC's on same server in Operating System - HP-UX

Multiple NIC's on same server

David Johnson_5 — Thu, 01 Aug 2002 18:08:22 GMT

I have Thre NIC in my HP 9000 running HP-UX 11.0

I want to know if I can force certain out going traffic to use a certain NIC card.

I have software the uses the MAC address of my MIC and the MAC address of the remote NIC to cumminicate.

The remote system will only answer the correct MAC address.

hostname 172.xxx.xxx.200
hostname2 172.xxx.xxx.206
hostname3 172.xxx.xxx.207

Re: Multiple NIC's on same server

Kelli Ward — Thu, 01 Aug 2002 18:17:17 GMT

I'm not sure if this helps, but if the 3rd octet of each addres is different, you can do it by setting the subnet mask on each card. Dependingf on how you are using your network, this might not be the best alternative for you and it will probably not do much for your 2 communicating NIC's.
Can you elaborate a bit on what you are doing?
Good luck,
Kel

Re: Multiple NIC's on same server

Sajid_1 — Thu, 01 Aug 2002 18:21:26 GMT

Hi,

You could check the TKB document - KBRC00006961:
http://support1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=500000000092418

OR do a search on the ITRC forums with "multiple+network+card+same+system"

Re: Multiple NIC's on same server

Rich Wright — Thu, 01 Aug 2002 18:25:37 GMT

We did this by establishing a private lan using 192.168.xxx.xxx.
Then traffic to 192.168.xxx.xxx gos out the NIC with a 192.168.xxx.xxx IP.
Traffic to 172.xxx.xxx.xxx goes out the NIC with a 172.xxx.xxx.xxx address assigned to it.

Rich

Re: Multiple NIC's on same server

rick jones — Fri, 02 Aug 2002 16:56:25 GMT

um, if you are communicating using only MAC addresses, you would be addessing the devices throgh DLPI and specifying the PPA when you did the "attach"

if you mean to say that you send and receive IP traffic, but the IP traffic is only accepted from a given MAC then...

...in general, it is not a good idea to configure multiple physical NICs into the same IP subnet. by default, all will be used for inbound, only one (the first ifconfig'd iirc) will be used for outbound.

you can use Auto Port Aggregation to put all three NICs into a single logical NIC. that NIC will be given one MAC address, based on the MAC address of one of the interfaces. That may change if the NIC used to select the MAC goes down.

...you can setup explicit host routes for machines, pointing at the specific local interface. if the number of machines is small, this is tractable.

...if your application binds to a local IP before calling connect() (on the multiple-NIC system) or if your application accepts connections from remote systems, you could set ip_strong_es_model to one - in this case, source IP address is used as part of route selection.

Re: Multiple NIC's on same server

sven verhaegen — Mon, 05 Aug 2002 11:33:39 GMT

I don't know if you are aware but 127.x.x.x number with netmask 255.0.0.0 is illegal on multiple interfaces on the same HP-UX due to the problem of interface identification at an IP level, this creates some strange routing effects with packets entering the system , the kernel will have problem discerning them and could misjudge , in any case any physical interface should use a different subnet then other physical interfaces and then you always route trough the correct interface due to the nature of the routing table and forwarding rules... this isn't valid for virtual interface implementations ,this special case is when Aliassing interfaces is used but then still the mac address is identical for any of the 3 IP addresses so there is no routing issue at all and your appliaction should work fine

Re: Multiple NIC's on same server

Joaquin Gil de Vergara — Mon, 05 Aug 2002 11:55:32 GMT

If you has three card on the same server belonging at the same subnet you can have troubles of routing

Segment the network in subnetworks (and use VLAN in the backbpone switch to improve performance avoiding flooding)or use APA software to aggregate it

Segmenting the net you ensure that each card always communicate with the correct system
With the aggregation (APA) it doesn??t work beacuse the MAC address will be changed