Intel 4-port ethernet adaptor link aggregation issue

[Joe Moog]

On Aug 1, 2013, at 6:16 PM, John-Mark Gurney <jmg at funkthat.com> wrote:

> Joe Moog wrote this message on Thu, Aug 01, 2013 at 17:14 -0500:
>> On Aug 1, 2013, at 4:27 PM, Joe Moog <joemoog at ebureau.com> wrote:
>> 
>>> On Aug 1, 2013, at 3:55 PM, Ryan Stone <rysto32 at gmail.com> wrote:
>>> 
>>>> Have you tried using only two ports, but both from the NIC?  My suspicion would be that the problem is in the lagg's handling of more than 2 ports rather than the driver, especially given that it is the igb driver in all cases.
>>> 
>>> Ryan:
>>> 
>>> We have done this successfully with two ports on the NIC, on another hardware-identical host. That said, it is entirely possible that this is a shortcoming of lagg. 
>>> 
>>> Can you think of any sort of workaround? Our desired implementation really requires the inclusion of all 4 ports in the lagg. Failing this we're looking at the likelihood of 10G ethernet, but with that comes significant overhead, both cost and administration (before anybody tries to force the cost debate, remember that there are 10G router modules and 10G-capable distribution switches involved, never mind the cabling and SFPs -- it's not just a $600 10G card for the host). I'd like to defer that requirement as long as possible. 4 aggregated gig ports would serve us perfectly well for the near-term.
>>> 
>>> Thanks
>>> 
>>> Joe
>> 
>> UPDATE: After additional testing, I'm beginning to suspect the igb driver. With our setup, ifconfig identifies all the ethernet ports as igb(0-5). I configured igb0 with a single static IP address (say, 192.168.1.10), and was able to connect to the host administratively. While connected, I enabled another port as a second standalone port, again with a unique address (say, 192.168.1.20), and was able to access the host via that interface as well. The problem arises when we attempt to similarly add a third interface to the mix -- and it doesn't seem to matter what interface(s) we use, or in what order we activate them. Always on the third interface, that third interface fails to respond despite showing "active" both in ifconfig and on the switch.
> 
> Can you show an ifconfig -au from the host when it fails, and which was
> the third interface that you added?  Above, you talk about adding ips in
> the same subnet to different interfaces, which with modern switchs can
> cause issues with which port to deliver packets, etc.
> 
> Do you have any firewalling enabled on the host?
> 

There are no firewalls enabled on the host.

I don't know that I see the switch as being the weak point in this setup as we have been very successful multihoming boxes with these switches for a variety of other purposes. I will collect and forward "ifconfig -au" output from the host in a couple of days, as we have had to fall back on the 2-port lagg to get this particular host in service until such time the 4-port lagg issue can be resolved. We will be setting up another hardware-identical host in a lab for further testing and info gathering.

Thanks

Joe