[c-nsp] "speed nonegotiate" command under optical transceiver configuration

[Martin T]

Hi,

one can apply "speed nonegotiate" command under interface
configuration mode in case of optical SFP/GBIC. Looks like this
command is supported only in case of optical transceivers. For example
I have a Cisco WS-C3750G-12S switch and if I insert copper SFP to port
Gi1/0/2, I do not have "speed nonegotiate" command available:

C3750(config-if)#do sh int Gi1/0/2 status

Port      Name               Status       Vlan       Duplex  Speed Type
Gi1/0/2                      notconnect   1            auto   auto
10/100/1000BaseTX SFP
C3750(config-if)#speed ?
  10    Force 10 Mbps operation
  100   Force 100 Mbps operation
  1000  Force 1000 Mbps operation
  auto  Enable AUTO speed configuration

C3750(config-if)#speed


Now if I remove the copper SFP and insert optical SFP or do not insert
nothing at all, I have "speed nonegotiate" command available:

C3750(config-if)#do sh int Gi1/0/2 status

Port      Name               Status       Vlan       Duplex  Speed Type
Gi1/0/2                      notconnect   1            auto   auto
1000BaseLX SFP
C3750(config-if)#speed ?
  nonegotiate  Do not negotiate speed

C3750(config-if)#speed


In addition, I have one one optical SFP with modified EEPROM so that
it appears as an copper SFP to the switch and thus "speed nonegotate"
command is not available:


 C3750(config-if)#do sh int Gi1/0/2 status

Port      Name               Status       Vlan       Duplex  Speed Type
Gi1/0/2                      notconnect   1            auto   auto
10/100/1000BaseTX SFP
C3750(config-if)#speed ?
  10    Force 10 Mbps operation
  100   Force 100 Mbps operation
  1000  Force 1000 Mbps operation
  auto  Enable AUTO speed configuration

C3750(config-if)#speed


Same behavior can be seen on Cisco 4500 platform where optical
GBIC's(on WS-X4306-GB module) support "speed nonegotiate" command and
copper GBIC's(WS-G5483) do not. 1000BASE-SX or 1000BASE-LX10 support
only 1GigE mode so there should be nothing to negotiate in terms of
speed..

In practice, I have used "speed nonegotiate" command in case I connect
Cisco optical SFP to a media-converter and I have heard that
connecting optical transceivers to non-Cisco gear (sometimes) require
"speed nonegotiate" command. Otherwise link will not come up.

Am I correct, that "speed nonegotiate" is available only on optical
transceivers? What is the history behind "speed nonegotiate" command?
What information is exchanged and expected by Cisco device if "speed
nonegotiate" command is not applied?



regards,
Martin