[nsp] Ethernet errors on 806?

sthaug at nethelp.no sthaug at nethelp.no
Fri Nov 14 13:43:53 EST 2003

We have a number of 806 (Ethernet-Ethernet) routers that all seem to
show the same problem:

- The routers are connected to various kinds of DSL "modems", which
typically have a 10 Mbps port with autonegotiation.

- The routers negotiate half duplex on the port connected to the DSL
modem (the router ports can only to 10 Mbps).

- The routers show output errors on the port connected to the DSL modem.
The packet error rate is typically around 0.25 to 0.5 percent. The errors
are real, there is measurable packet loss for traffic through the routers.
This happens whether the routers negotiate half duplex, or is configured
to half duplex with the CLI.

- Setting the port to full duplex (IOS CLI lets you do this) makes the
output errors disappear, but now we get input errors (CRC errors) instead. 

Neither the "duplex half" nor the "duplex full" setting is reflected in
"show run" or the saved configuration file. However, the commannds seem
to have *some* effect, since the error type changes. This seems like an
obvious IOS bug.

This problem happens with several different IOS versions, most recently
with 12.2(15)T9. If it had only happened with one type of DSL modem, I
would have been tempted to blame the DSL modem - but it happens with
several different types of DSL modems from several manufacturers.

Does anybody know whether 806 routers afflicted with some kind of 
generic Ethernet problem? We don't seem to have the same problem with
our 831 Ethernet-Ethernet routers.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no

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