Auto-Negotiation and Port Advertised Ability

Auto-negotiation is an Ethernet feature that facilitates the selection of port speed, duplex, and flow control between the two members of a link, by first sharing these capabilities and then selecting the fastest transmission mode that both ends of the link support. Auto-negotiation is enabled by default.

The advertised ability feature allows for the port to share its port capabilities with the other end of the link. Advertised capabilities will be used during the auto-negotiation process. Actual port capabilities, advertised port capability and remote end advertised port capabilities can be displayed using the show port advertise command in any command mode. The following port capabilities can be advertised:

• 10t - 10BASE-T half duplex mode
• 10tfd - 10BASE-T full duplex mode
• 100tx - 100BASE-TX half duplex mode
• 100txfd - 100BASE-TX full duplex mode
• 1000x - 1000BASE-X, -LX, -SX, -CX half duplex mode
• 1000xfd - 1000BASE-X, -LX, -SX, -CX full duplex mode
• 1000t - 1000BASE-T half duplex mode
• 1000tfd - 1000BASE-T full duplex mode
• pause - PAUSE for full-duplex links
• apause - Asymmetric PAUSE for full-duplex links
• spause - Symmetric PAUSE for full-duplex links
• bpause - Asymmetric and Symmetric PAUSE for full-duplex links
  

  Note

  Advertised ability can be activated only on ports that have auto-negotiation enabled.

During auto-negotiation, making use of information gained from the advertised ability feature, the port “tells” the device at the other end of the segment what its capabilities and mode of operation are. If auto-negotiation is disabled, the port reverts to the values specified by the default speed, default duplex, and the port flow control commands.

Use the set port negotiation command to enable auto-negotiation on the specified ports.

Use the set port advertise command to specify the capabilities to be advertised on the specified ports.

The following example enables auto-negotiation on port ge.1.1 and sets the advertise utility to advertise 10BASE-T half duplex mode, 10BASE-T full duplex mode, 100BASE-TX half duplex mode, 100BASE-TX full duplex mode, and Asymmetric and Symmetric PAUSE for full-duplex links:

System(rw)->set port negotiation ge.1.1 enable
System(rw)->set port advertise ge.1.1 10t 10tfd 100tx 100txfd bpause
System(rw)->show port advertise ge.1.1
ge.1.1       capability   advertised    remote
----------------------------------------------
10BASE-T         yes         yes         yes
10BASE-TFD       yes         yes         yes
100BASE-TX       yes         yes         yes
100BASE-TXFD     yes         yes         yes
1000BASE-X       no          no          no
1000BASE-XFD     no          no          no
1000BASE-T       no          no          no
1000BASE-TFD     no          no          no
other            no          no          no
pause            yes         no          yes
Apause           yes         no          no
Spause           yes         no          yes
Bpause           yes         yes         no
System(rw)->