[nSLUG] Router won't do 100mbps locally

Mike Spencer mspencer at tallships.ca
Thu Feb 4 03:26:39 AST 2010


So I finally got two computers with network cards that support
100baseT and which are responsive to ethtool.  They're cable-connected
to a D-Link DI-713P router (advertised as 10baseT and 100baseT
compliant.)

So, with ethtool, I force both cards to "autoneg off duplex full speed
100".  The blinkenlights on the router go into continuous twiddle
mode.  No packets are detected by tcpdump.  So the cards are trying to
establish a 100Mbps connection with the router at the Ethernet level
(right?)  and failing (right?).

While this state continues, neither host is reachable from the other.
A similar condition arises if I let the cards auto-negotiate. The
blinkenlight twiddle never stops and no IP connection can be made
between computers.

Resetting the cards with "ethtool....speed 10" results in a connection
with an actual transfer rate (by calculation from a quickie script) of
9.1Mbps.

Is there some arcanum that I need to know?

         Example arcanum that I ruled out:

         Older routers may not support Explicit Congestion
         Notification (RFC 3168) but sysctl shows this disabled in my
         2.4 kernel and source code shows it as a disabled option in
         the driver module.

Or is the best surmise that the router is failing (more or less)
gracefully?

The router's admin interface doesn't have any means to force it to a
particular speed.

FWIW, here's the tech info

  root# ethtool eth0

  Settings for eth0:
    Supported ports: [ TP MII ]
    Supported link modes:   10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Supports auto-negotiation: Yes
    Advertised link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
    Advertised auto-negotiation: No
    Speed: 10Mb/s
    Duplex: Full
    Port: MII
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: off
    Current message level: 0x000020c1 (8385)
    Link detected: yes

[Same for both cards. Everything works at ca. 10Mbps with these settings.]

  bogus-root# lspci |grep Ethernet

    01:08.0 Ethernet controller: Intel Corp. 82801BA/BAM/CA/CAM Ethernet
            Controller (rev 01)

  nudel-root# lspci |grep Ethernet

    01:08.0 Ethernet controller: Intel Corporation 82562EZ 10/100 Ethernet
            Controller (rev 02)


Modules [both boxen]:

     eepro100
     mii         [eepro100]


Advice? TIA,
- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^



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