Ierrs with netstat -in and lanadmin

[Jannik]

I have a server generating errors.
If I do a netstat -in I can se a lot of Ierrs.
The interface is set to 100FD manual.

netstat -in
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lan0 1500 172.16.1.0 172.16.1.13 33120558 49837 38252740 0 0
lo0 4136 127.0.0.0 127.0.0.1 612916 0 612916 0 0

[Peter Godron]

Hi,
double check your setup with lanadmin, but
as you are not getting collisions, I would suspect the cable.

[spex]

Hi,

Notice that Oerrs=0, even though there were more outbound packets than inbound. This suggests a problem with the NIC's network settings, or maybe a problem with the port configuration in the switch.

Use 'lanadmin' and /etc/rc.config.d/netconf to check settings. Apply changes with '/sbin/init.d/net stop && /sbin/init.d/net start' from the console.

PCS

[Ron Kinner · Accepted solution]

Incoming errors on a Full Duplex setup usually indicate the other end of the cable is set to Half Duplex. What happens is that the other end is happily sending you a packet when your side (knowing that it is full duplex and thus it need not check to see if the other side is sending) starts sending a packet. The other side sees your output and panics since it thinks this is a half duplex circuit so in order to reduce the collision to a minimum it stops sending in mid packet. This partial packet will be received by your box as an error since it won't be complete.

Remember that if you manually set one side to Full you MUST set the other side manually to Full. Otherwise I guarantee that it will set up as half. (It has to if it follows the spec since only if both sides are set to AUTO is it allowed to go to FULL automatically.)

Ron

[rick jones]

$ cat usenet_replies/duplex
How 100Base-T Autoneg is supposed to work:

When both sides of the link are set to autoneg, they will "negotiate"
the duplex setting and select full-duplex if both sides can do
full-duplex.

If one side is hardcoded and not using autoneg, the autoneg process
will "fail" and the side trying to autoneg is required by spec to use
half-duplex mode.

If one side is using half-duplex, and the other is using full-duplex,
sorrow and woe is the usual result.

So, the following table shows what will happen given various settings
on each side:

Auto Half Full

Auto Happiness Lucky Sorrow

Half Lucky Happiness Sorrow

Full Sorrow Sorrow Happiness

Happiness means that there is a good shot of everything going well.
Lucky means that things will likely go well, but not because you did
anything correctly :) Sorrow means that there _will_ be a duplex
mis-match.

When there is a duplex mismatch, on the side running half-duplex you
will see various errors and probably a number of _LATE_ collisions
("normal" collisions don't count here). On the side running
full-duplex you will see things like FCS errors. Note that those
errors are not necessarily conclusive, they are simply indicators.

Further, it is important to keep in mind that a "clean" ping (or the
like - eg "linkloop" or default netperf TCP_RR) test result is
inconclusive here - a duplex mismatch causes lost traffic _only_ when
both sides of the link try to speak at the same time. A typical ping
test, being synchronous, one at a time request/response, never tries
to have both sides talking at the same time.

Finally, when/if you migrate to 1000Base-T, everything has to be set
to auto-neg anyway.

[Jannik]

tnx