Frequent pauses with Linux-based router

[David DeSimone]

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Sean C. Farley <scf at FreeBSD.org> wrote:
>
> An ICMP test showed that there were occasional pauses and packet loss. 
> The fix:  use 100Mb instead of 10Mb.  :) For some reason I do not
> recall, I had forced the interface connected to the DSL router to
> 10Mb.  When I noticed XP did not have the same problem and that it had
> a 100Mb connection to the router, I found and removed the "media
> 10baseT/UTP mediaopt full-duplex" from /etc/rc.conf for the interface. 
> That appears to have fixed it.

The fix here is not that you moved to 100 Mb, it's that you stopped
forcing duplex, and allow auto-negotiation to take place.

With the forced duplex in effect, your NIC does not auto-negotiate with
the other end (the router), and it falls back to half duplex, which
leads to large numbers of collision errors.

> The pause always seemed to be for packets from the router to the
> computer.

Yep, whenever the router would try to send, if your end happened to be
sending a frame, the router's NIC would stop to avoid the collision,
leading to packet loss.  This is a classic duplex-mismatch scenario.

- -- 
David DeSimone == Network Admin == fox at verio.net
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