topic Re: 3 NICs in Operating System - HP-UX

3 NICs

Mike Boswell_1 — Mon, 19 Jul 2010 14:10:43 GMT

I need help understanding why certain network traffic are using lan900(lan1 and lan2) while other traffic uses lan0. for instance traffic on 172.20.x.x uses lan900 while 172.18.1.x uses lan0 as seen from 'lsof'

root@pigpen:/> netstat -rn
Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 4136
172.20.20.67 172.20.20.67 UH 0 lan900 4136
172.18.1.73 172.18.1.73 UH 0 lan0 4136
172.18.1.0 172.18.1.73 U 2 lan0 1500
172.20.20.0 172.20.20.67 U 2 lan900 1500
127.0.0.0 127.0.0.1 U 0 lo0 0
default 172.20.20.250 UG 0 lan900 0

root@pigpen:/> lanadmin -x -v 900
Link Aggregate PPA # : 900
Number of Ports : 2
Ports PPA : 2 1
Link Aggregation State : LINKAGG MANUAL
Group Capability : 5
Load Balance Mode : MAC Address based (LB_MAC)

Re: 3 NICs

Steven E. Protter — Mon, 19 Jul 2010 14:42:28 GMT

Shalom,

lan0 is probably defined as the default gateway on your system. That is why some traffic goes on it, in spite of your APA configuration.

Take a look at nwmgr output for more data here.

A good way to get all traffic to go over your aggregate LAN is to build an aggregate including all interfaces.

Right now you are not really load balancing. To support LB_MAC load balancing, you will need to have your switch configuration adjusted to accommodate this.

SEP

Re: 3 NICs

Mike Boswell_1 — Mon, 19 Jul 2010 15:03:10 GMT

Thanks. Looks like I misunderstood my APA setup.

Can you help me dig a bit deeper into lan0. I would like to unplug it but that results in some networks being unreachable.

Mike

Re: 3 NICs

Steven E. Protter — Mon, 19 Jul 2010 15:47:48 GMT

Shalom,

No, do not unplug lan0.

Go through the APA configuration guide and set up an Aggregate network that includes lan0.

Then lan0 traffic will be lan900 traffic, even in manual mode.

SEP

Re: 3 NICs

Mike Boswell_1 — Mon, 19 Jul 2010 16:23:16 GMT

Thanks Steven,
I would like to disable/remove the lan0 connection. The APA has 2 links now. We really dont need the 3rd. So I would like unplug and have all traffic route thru the APA but when we unplug it we loose some connectivity. I would like to figure out why this lan0 has any traffic at all and config it out of any use.

Mike

Re: 3 NICs

rick jones — Tue, 20 Jul 2010 16:37:35 GMT

Conceptually speaking, when the transport stack goes to figure-out how to reach a given destination IP address, it will first look for a matching host route, then a matching (sub)network route and then finally the default route. So, given the initial routing table, lan0 is in a 172.18.1 subnet (would want to see the netmasks from ifconfig lan0 to know precisely but I'm guessing it is 255.255.255). If the destination IP happens to be in 172.18.something then lan0 will have the matching subnet route and will be used rather than lan900, which appears to be a different subnet.

If you simply unplug lan0 and do not bring it down and/or unplumb it, it could be that the routing code takes a while to decide that route is no good. Assuming that 172.20.20.250 knows how to reach the 172.18.1 subnet, if you ifconfig lan0 0.0.0.0 traffic should start flowing via your lan900 interface.