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Community Member

Auto-negotiation on 1000-Base-SX

Hello,

This is continuation of my previous posts here.

I did a lot of research, but I have a problem finding one thing: Is auto-negotiation mandatory on 1000BaseX (i.e 1000BaseSX) interfaces? (in other words, should every 1000BaseX interface support auto-negotiation function))

I did a search through a lot of annexes of 802.3 standard (from 2004, 2005, 2006) but I can't find any sentence that actually says: Auto-negotiation function MUST be supported by every 1000BaseX

If you guys have any link to any documents that shows me autonegotiation function requirements, I would be more than thankful.

Cheers

M.

2 REPLIES
Cisco Employee

Re: Auto-negotiation on 1000-Base-SX

Hello Milos,

The 1000-Base-X SFP modules operates only 1000 Mbps and duplex options are not supported. however, to avoid auto-negotiation you can use " nonegotiate " keyword under the interfaces.

Speed and Duplex Configuration Guidelines

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_44_se/configuration/guide/swint.html#wp1028628

Excerpt from the above link

For SFP module ports, the speed and duplex CLI options change depending on the SFP module type:

-The 1000BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support the nonegotiate keyword in the speed interface configuration command. Duplex options are not supported.

=================

HTH

Padmanabhan

Community Member

Re: Auto-negotiation on 1000-Base-SX

Hello Padmanabhan,

Thanks for your answer, but I have one more thing. When you look to the commands (config-if)#speed nonegotiate or (config-if)#no negotiate auto, you will see that Cisco says that these commands are not used for setting speed negotiation, but duplex/flow control and remote failures (whatever that be).

I tried to read IEEE 802.3 annex 2005 part 3 which has something like 50 pages about auto-negotiation function on 1000Base-X interfaces, but the thing is, I can't find (maybe I need new glasses) any keyword MUST, or REQUIRED to use.

So, basically, the thing is I can't find is autonegotiation function MANDATORY or OPTIONAL (and should GBIC/SPF manufacturers and/or OS manufacturers follow this standard and create auto-negotiate capable interfaces or not).

Thanks for your replies.

Cheers

M.

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