Ethernet Fabric (VDX, CNA)

Senior Member
Posts: 1
Registered: ‎11-05-2014


[ Edited ]

First of all, I'm novice with Brocade. I'm progressing well with a Brocade VDX6740T fabric testing comprising of 2 switches. The switches are now running NOS 4.1.3 (upgraded from the factory 4.0.1), I've got the fabric setup, including lacp (bonding mode 4) and is working mostly fine. So far, the only issue I found is a rather peculiar behaviour I don't remember noticing when testing a single demo switch in our lab, which was running 4.1.0. It's related to 10Gb interface speed auto-negotiation when the systems connected are running at 1Gbps, not 10.
Because we don't have in our lab systems with dual 10Gb adapters, I'm using 3 servers with 2x1Gbps cards, one acting as iSCSI target while the other two are initiators. Two of the 3 servers are experiencing the issue, the 3rd one looks fine. Here's a description of the behaviour:
- When I first saw the autoneg issue I tried forcing the speed on the TenGigabitEthernet to 1000, instead of the auto value, which one would expect to work. I thought this fixed the problem in the test environment, but it didn't completely, because:

- When rebooting the servers, 2 out of 3 lose their ethernet connections into the Brocades, with both Brocades in the fabric logging a message like this for each of the interfaces directly connected to the affected server:
"BOM Interface TenGigabitEthernet 1/0/3 is administratively down due to speed mismatch in port-channel."

On Linux ethtool shows no link for both interfaces. To get the links back up I have to log into one of the Brocades and run:
ddnsVDX1(config)# interface TenGigabitEthernet 1/0/1-48
ddnsVDX1(conf-if-te-1/0/1-48)# no shutdown
ddnsVDX1(conf-if-te-1/0/1-48)# interface TenGigabitEthernet 2/0/1-48
ddnsVDX1(conf-if-te-2/0/1-48)# no shutdown
Then the testing resumes fine, but the connection won't survive a server reboot, after which the connected Brocade ports must be issued "no shutdown" again.

The major differences between testing the demo and the 2 new switches are:

1. Different NOS versions: 4.0.1 on the demo, 4.1.3 on the current ones.

2. Single switch vs. dual switch fabric.

3. Licensing(?) I dind't have to enter any license key on the 2 new switches, whereas the demo one had a license installed.

What other information do you want me to provide?


Posts: 10
Registered: ‎06-01-2011

Re: [VDX6740T]

[ Edited ]

This is a well known behaviour !

You should never ever configure the speed on the physical interfaces of a port channel !

ONLY on their corresponding port channel interface !!

This makes sense cause it prevents having config mismateches on the corresponding ports to a port channel.


If you set the speed on the port channel only your port channel will come up instantly ! ;-)

Licensing is only needed for FCOE and ports on demand. For nothing else.


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