Question : Duplex.. full, half, auto?

We seem to be having issues with our LAN. As you can see in the logs below we are getting errors and dropped packets.
Here are the logs from the trusted interface of our router and also the logs from our traffic monitor which is showing the duplex changing from half to full frequently for device IP 192.168.1.11.
Pease have a look and let me know what you think could resolve this.
Thanks for the help.
JC

eth1 Link encap:Ethernet HWaddr 00:90:7F:2E:D5:C7
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:2
RX packets:257412 errors:207 dropped:0 overruns:207 frame:0
TX packets:329778 errors:0 dropped:2112 overruns:0 carrier:0
Collisions:0
Interrupt:5 Base address:0xc000



02/19/05 19:59 kernel: eth1: Setting half-duplex based on MII #32 link partner ability of 0000.
02/20/05 04:15 kernel: eth1: Setting full-duplex based on MII #32 link partner ability of c5e1.
02/20/05 04:15 dhcpd[130]: DHCPACK on 192.168.1.11 to 00:0f:1f:d0:e4:10 via eth1
02/20/05 04:45 dhcpd[130]: saved DHCP lease database
02/20/05 05:22 kernel: eth1: Setting half-duplex based on MII #32 link partner ability of 0000.
02/20/05 20:10 dhcpd[130]: DHCPACK on 192.168.1.11 to 00:0f:1f:d0:e4:10 via eth1
02/20/05 20:10 kernel: eth1: Setting full-duplex based on MII #32 link partner ability of c5e1.

Answer : Duplex.. full, half, auto?

If you do a search in here for "autonegotiate problems" or "duplex settings" I'm sure you'd come across many of my posts on this topic - it seems to be pretty misunderstood.

When an autonegotiate device is connected to a full duplex device on the other end, the Auto side will say to itself (by design I may add) - the other side doesn't want to negotiate, since it's not responding to my negotiate pulses - it must not be able to operate at full duplex, so I'd better set myself to half duplex.

Autonegotiate ---- Autonegotiate = 100 Full Duplex (most of the time, but it depends - watch for problems)
100 Full ----- Autonegotiate = Duplex mismatch 100 Full and 100 Half.  One side will see CRC and Alignment errors.  Other side sees collisions and giants.
Autonegotiate ---- 100 Full = Duplex mismatch.
100 Full ----- 100 Full = no problems related to duplex negotiation or line speed matching.

If you have servers and mangeable equipment I like to set all servers at 100 Full.  if you have PC's which don't move, I like them to be 100 Full.  If you have laptops which go home and plug into SOHO gear at home, such as a Linksys router, make them Autonegotiate.

If you ONLY have unmanaged network equipment, and you can't set ports to 100 Full Duplex for optimal networking at that speed, you MUST set everything to Autonegotiate.

Hope this helps.