WLBS web servers lose connectivity through switch

[Chris Stevenson]

I have 2 IIS5.0 web servers communicating with a SQL
Server 2000 Cluster through Cisco6500 "Port Channelled"
switches. We have Adaptec DuraLAN dual port "teamed"
adapters. My web servers seem to lose connectivity to
the database servers. The switch traffic shows that the
adapters on one of my servers don't show a corresponding
MAC address to the IP address.

Are there any known issues with using Cisco Fast
Etherchannel along with NLB? Or any issues with Teamed
Network adapters over Port Channeled switch ports with
NLB servers?

Thanks.
C

 

[Sean [MS]]

Hi Chris -

Can you send some more information about your setup? How many NICs per
severs? To which NICs are NLB bound? Which NICs are teamed? Basically, a
"picture" of your network would help.

However, first and foremost, yes, there are known issues with NLB and NIC
teaming. I assume that you have created a NIC team on each of your NLB
servers and bound the NLB service to the virtual teamed NIC, correct? Though
there are a lot of people out there trying to do this, it is officially
unsupported, but can usually be made to work. The primary issue is that NLB
tries to alter the MAC address of the NIC to which it is bound, in this case
the virtual teaming NIC, and the NIC teaming software doesn't seem to like
that very much. The physical NICs in the team often fail to recognize the
new MAC address and connectivity is intermittent at best. There can also be
problems caused by teaming software that "heartbeats" to improve failover
detection (Compaq, for one).

The workaround is to turn off any heartbeating that is being done by the
teaming driver (in the teaming UI), if any, and to manually set the NLB MAC
address on the virtual teaming NIC on each NLB server. You can find the NLB
MAC address in the NLB UI (usually starts with 02-bf... or 03-bf...). You
need to go to the teaming software, locate your team, and explicitly set the
team MAC address to the NLB MAC address. If the teaming software does not
allow this, then it is incompatible with NLB. Note also that if you ever
change the primary cluster IP address of your NLB cluster, you change the
MAC address and would need to update the MAC address in the teaming
configuration. It's this required hoop-jumping that causes this to be
unsupported by Microsoft. Technically, it's a bug in the teaming software
that they ALL exhibit - the problem is that the fix is non-trivial for them.

Anyway, see KB article 278431
(http://support.microsoft.com/default.aspx?scid=kb;en-us;278431) for further
information. Hope this helps.

Cheers, Sean