3Com 3C13636 Configuration Manual page 257

3Com Router 3000 Ethernet Family
Configuration Guide
Note:
By default, both operating speeds and modes of FE and GE electrical interfaces are
negotiation. You can force to change the operating speeds and modes, but should
keep the speed and mode the same as those of the peer end.
If you force to execute the duplex negotiation or speed negotiation command,
the Ethernet electrical interfaces are set to the negotiation mode, and negotiate
speed and duplex mode.
In terms of GE electrical interfaces, the operating speed 1000Mbps and half-duplex
mode are mutually exclusive. Thus, you cannot set these two values at the same
time.
V. Selecting an operating mode for an Ethernet interface
As mentioned earlier, an Ethernet interface can work at both full-duplex mode and
half-duplex mode. Connected to a hub, the Ethernet interface on a router must be
specified to work in half-duplex mode. Connected to a LAN Switch, however, it must be
specified to work in full-duplex mode. Both FE and GE electrical interfaces support
these two modes, whereas FE and GE optical interfaces can only work in full-duplex
mode.
Perform the following configuration in Ethernet interface view to select an operating
mode.
Table 2-5 Select an operating mode for the FE interface
Select an operating mode for the FE interface
By default, negotiation is set on both FE and GE electrical interfaces. That is, the
system automatically negotiates an optimum operating mode.
Note:
In terms of GE electrical interfaces, the operating speed 1000Mbps and half-duplex
mode are mutually exclusive. Thus, you cannot set these two values at the same time.
VI. Enabling or disabling loopback
Sometimes, you need to enable local loop on an interface for testing some special
functions. Perform the following configuration in Ethernet interface view to enable an
interface to make local loopback.
Operation
3Com Corporation
2-4
Chapter 2 LAN Interface Configuration
Command
duplex { negotiation | full | half }