Fibre Channel (SAN)

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New Contributor
Posts: 2
Registered: ‎07-27-2010

4Gbit ISLs auto-negotiate now at 2Gbit

We started off with a 5-switch tape SAN consisting of a brocade 12000 (seen as 2 switches), a brocade 4900, and a brocade 4100 in one building, and an additional brocade 4100 in a building several kilometers away.  3 ISLs on the brocade 12000 and 2 ISLs on the local 4100 communicated with 5 ISLs on the remote 4100 over 5 pairs of single-mode fiber.  The 3 ISLs between the 12000 and the remote 4100 ran at 2Gbit while the 2 ISLs between the local 4100 and the remote 4100 ran at 4Gbit, to be expected as the 4100s are 4Gbit switches but the 12000 cannot run faster than 2Gbit.

We recently consolidated this 5-switch SAN into 3 switches.  We moved all devices off the 12000 and the local 4100 and onto the existing 4900 and an additional 4900.  So we now have a SAN consisting of a pair of local 4900s plus the remote 4100.  We only found enough long-wave SFPs to use 4 out of 5 pairs of single-mode fiber, so we put 2 ISLs in each 4900, expecting to light up the ISLs on the remote 4100 at 4Gbit each.  For some reason, though, the 4 ISLs we now have auto-negotiate at 2Gbit.  Attempts to force a 4Gbit speed cause the switch to mark the ports as "marginal".

We would very much like to have the 4Gbit bandwidth for each of the ISLs.  Since the 4100 and the  4900 are both 4Gbit switches, why do they not auto-negotiate at 4Gbit?  The firmware on the remote 4100 is v5.0.4a while the firmware on the local 4900s is v5.3.0 .  Anyone out there have any ideas?

Occasional Contributor
Posts: 16
Registered: ‎11-22-2009

Re: 4Gbit ISLs auto-negotiate now at 2Gbit

I would be suspicious of the SFPs used in these ports that only work at 2G.

use 'sfpshow' command to see the capability of the SFP in the port..

i.e.

Port 11: id (sw) Vendor: FINISAR CORP.    Serial No: PDE4H5R          Speed: 100,200,400_MB/s
Port 12: id (sw) Vendor: FINISAR CORP.    Serial No: P1124YK          Speed: 100_MB/s

in this example port 11 is 100, 200, 400 (1G, 2G, 4G) capable

whereas port 12 is only a 1G capable SFP.

Super Contributor
Posts: 260
Registered: ‎04-09-2008

Re: 4Gbit ISLs auto-negotiate now at 2Gbit

how far is the building with the 4100??

post output of portbuffershow??

have you installed a Extended Fabric license??

Super Contributor
Posts: 644
Registered: ‎03-01-2007

Re: 4Gbit ISLs auto-negotiate now at 2Gbit

adina,

--->>> .....and a brocade 4100 in one building, and an additional brocade 4100 in a building several kilometers away.

what is the exact Distance beetwen both building ?

By "kilometers" you have to use LongWave SFP, and not ShortWave this work only till 550mt by 1GB

If you are unsure, please provide to post sfpshow output here.

Thank You.

New Contributor
Posts: 2
Registered: ‎07-27-2010

Re: 4Gbit ISLs auto-negotiate now at 2Gbit

I think you have found our issue.

We seem to have a mix of 2Gbit and 4Gbit long-wave SFPs in use.  The first 4900's long-wave SFPs are both 2Gbit.  The second 4900's SFPs are both 4Gbit.  On the remote 4100, only one long-wave SFP is 4Gbit, and I'm betting it's talking to a 2Gbit SFP on this side.

Thanks much for your help!!  :-)

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