FC3 with BEFSR11 Linksys router slow connection

[Rick Stevens]

Shawn Iverson wrote:
> On Monday, March 21, 2005 10:00 AM David Hoffman wrote:
> 
>>Well, first thing to remember is rule number one of 
>>networking... "You are only as fast as your slowest link".
> 
> 
> True, but even the 100baseTX/Full network at work must run as slow as
> the dual T1 lines when connecting to the Internet, and those LAN to
> Internet links experience no problems.
> 
> 
>>If you have a Cable or DSL modem on the other side of the 
>>Linksys, you know that you are not going to be getting more 
>>than 10Mbits of speed through them. DSL here in Houston 
>>(depending on what level you want to pay for) is either 
>>1.5Mbits, or 6.0 Mbits. Cable throughput will vary, but 
>>usually isn't going to be more than that.
>>
>>So is there any reason for your FC3 machine needs a 100Mbit 
>>connection to the switch?
> 
> 
> Possibly.
> 
> 
>>Also, the auto-sensing switch might let your FC3 machine do a 
>>Full Duplex connection to the switch, but if the Linksys is 
>>only Half-Duplex (while it SHOULD work fine) then having the 
>>FC3 at FD might not make a difference too.
> 
> 
> I performed a series of tests using mii-tool and found something strange
> about the Linksys router.  If the router is at 100 megabit full or half
> (auto-sensing switch in between), regardless of what I set the speed and
> duplex to on the Fedora box, I experience the same problems.  The
> connection is so slow it is nearly worthless, and the same layer 2
> errors appear on the TX line.  My first suspicion was the switch, but I
> have tried several already; when I connect directly to the Linksys, I
> still have the same trouble at 100 megabit.
> 
> I just discovered that it does work great, however, if I am connected
> directly to the Linksys and use the mii-tool to force the connection
> speed and duplex to either 10/half or 10/full.  The Linksys auto senses
> the server's setting and matches it after executing ifdown eth1 && ifup
> eth1.
> 
> The kicker is that I need a switch between the router and the server
> because it is sharing connections with other machines.  The switches I
> have are auto-sensing, so just as soon as I plug the Linksys into the
> switch, it gladly jumps to 100/Full.  The router setup page has no way
> to force speed and duplex, AFAIK, so it is stuck at 100, leaving me with
> the same problem with which I have been originally contending.
> 
> What could possibly be screwed up on the Linksys at 100 megabit as to
> cause Linux to have so much trouble?  Other operating systems, namely
> Windows, are not affected.  I am approaching a situation where I might
> have to find an old 10baseT switch lying around somewhere and use it
> instead.  On the other hand, it bothers me because the BEFSR11 model is
> fairly common, and who knows how many others could run into the same
> trouble.

The trick is that autonegotiation is somewhat ill-defined.  Windows
has hacks that work around issues such as you are having, but Linux
doesn't.

The solution is to force both ends to 100MbFD and turn off autosense.
We have similar issues with Cisco and Extreme Networks stuff on
occasion.  I agree it "should work" but it often doesn't, so we don't
even let them start the discussion.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-              Where there's a will, I want to be in it.             -
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