Subject: full duplex ethernet trouble
To: tech-userlevel <>
From: Dave <>
List: tech-userlevel
Date: 05/05/2004 17:44:14
I've finally upgraded to a 100baseTX switch and am having trouble getting
full-duplex ethernet working correctly.

For right now, the network is composed of two machines, both with Netgear
FA310TX NICs and a Netgear FS108 switch.

According to the switch, the cards are in full-duplex mode only when the
machines boot.  At this point, network performance is intolerably slow.

If a cable is removed and replaced or the switch powercycled, the FDX
light on the switch for that port goes out.  The lights on the cards still
claim they're in full-duplex mode.  Network performance is now acceptable,
but I'm not sure if I'm truly in full-duplex mode.

So, now my questions:
1) What is the reason for the odd behavior of the full-duplex lights on
the switch?

2) Why when any or both of these lights are on is the network performance
exceedingly slow?

3) Is the below output from ifconfig(8) enough to prove that the interface
is indeed in full-duplex mode?

4) How do I make the switch lights behave themselves?

5) How do I make sure the machines boot up such that their network
throughput isn't hindered by whatever gremlin is at work?

# ifconfig tlp0
        address: 00:a0:cc:d1:ce:ef
        media: Ethernet 100baseTX full-duplex
        status: active
        inet netmask 0xffffff00 broadcast
        inet6 fe80::2a0:ccff:fed1:ceef%tlp0 prefixlen 64 scopeid 0x1

# cat /etc/ifconfig.tlp0 netmask 0xffffff00 media 100baseTX
[note: appending "mediaopt full-duplex" made no difference.]

David Griffith