Bay Networks BayStack 303, User Manual

Page: 82 / 101

Using the BayStack 303 and 304 Ethernet Switches
4-2
893-01010-A
Autonegotiation
Port connection problems can occur when a port is connected to a station that is
not operating in a compatible mode (for example, connecting a full-duplex port to
a half-duplex port). Problems and mismatches occur when the switch is connected
to a port that either:
• Does not support autonegotiation.
• Supports a form of autonegotiation that is not compatible to the IEEE 802.3u
autonegotiation standard.
• Supports autonegotiation but has the feature disabled.
In the situations described here, the BayStack switches autosense the speed of the
connected port and, by default, revert to half-duplex mode. If the connected
station is operating in full-duplex mode, the stations cannot communicate
properly and a mismatch occurs. This mismatch can be resolved by disabling
autonegotiation and manually setting the speed and duplex mode (see
“Port
Configuration ” on page 3-14 to manually set speed and duplex mode).
When the link is first brought up, the BayStack 303 and 304 switches sense the
speed of the connecting device. If the connecting device changes speed without
performing a link down, the BayStack switch can correctly sense a change from
100 Mb/s to 10 Mb/s; however, it cannot sense a change from 10 Mb/s to
100 Mb/s. In the latter case, the switch reports 10 Mb/s operation and link up, but
the connecting device reports link down. This link mismatch can be resolved by
forcing the link down and up or by disabling autonegotiation and manually setting
the speed and duplex mode.
89301010.BK Page 2 Tuesday, June 10, 1997 8:00 PM