On Wed, Oct 19, 2005 at 12:28:09PM -0400, Harry Tirrell wrote:
> I am at a site with NBU 5.2 running on AIX 5.1, we would like to set the
> GigE interfaces to GigE Full Duplex. But we only GigE option we can find is
> autonegotiate. Does any one know of a way to this on AIX? Thanks in advance.
Interesting. Don't know of a way to do this on AIX.
Prevailing wisdom I was working to was that you shouldn't do it
(nail up speed/duplex) for GigE-capable interfaces on any OS/switch,
in contrast to normal practise for 10/100.
I'd be interested to hear of any experiences to the contrary; I
certainly know of cases where preventing GigE auto-negotiation
breaks stuff (even where 1000Base-T interfaces are plugged into a
10/100 port).
I can't vouch for this quote, but I got it off the Internet, so it
must be right[0]:
"The IEEE 802.3ab specification does not allow for forced
mode 1000BASE-T with autonegotiation disabled running at
1000 Mbps. As a result, many switch vendors do not support
forced mode.
Clause 40 (1000BASE-T), subclause 40.5.1 of 802.3 states:
All 1000BASE-T PHYs shall provide support for Auto-Negotiation
(Clause 28) and shall be capable of operating as MASTER or
SLAVE. Auto-Negotiation is performed as part of the initial
set-up of the link, and allows the PHYs at each end to
advertise their capabilities (speed, PHY type, half or full
duplex) and to automatically select the operating mode for
communication on the link.
This means that although autonegotiation is optional for
most variants of Ethernet and manual configuration (forced
mode) is allowed, this is not the case for Gigabit copper
(1000BASE-T)."
I haven't verified the above interpretation beyond checking that
the spec does actually contain that wording (2nd quoted para).
See for yourself:
http://standards.ieee.org/getieee802/download/802.3-2002_part3.pdf
Interestingly enough, an official IEEE interpretation of:
"I am debating with a colleague the validity of configuring a
10/100/1000 Ethernet port for fixed 1000Mb full-duplex operation.
Is this permissible? I have seen interpretations that it is permissible
to configure a port for fixed 1000Mbps operation and interpretations
that if auto-negotiation is disabled, fixed speed can only be set
to 100Mbps or 10Mbps."
Is "currently under development". Since March 05. See:
http://www.ieee802.org/3/interp/interp-2-0705.pdf
It's also true that GigE 1000Base-X interfaces have their own,
separate, section relating to link parameter auto-negotiation - so
there may even be separate rules for SX/LX optical interfaces, but
I couldn't deal with it anymore...
:)
Cheers,
AS
[0] Humor.
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