Network speed problems

Bhaskar Dutta bhaskie99 at yahoo.co.uk
Thu Apr 1 07:26:18 PST 2004


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  >>> On Thursday 01 Apr 2004 6:23 pm, JC <Jeroen Coumans> said:
    JC> Heya,
    JC> Anybody want to hit me with a cluebat to properly debug network speed
    JC> problems?
    JC>
    JC> The problem is on a LAN with several 100Mbps Linux boxes, routed by a
    JC> Cisco 3600 router running IOS 12.2(6c).
    JC>
    JC> The maximum speed to copy 5Mb of data never gets above 900K/s. That's
    JC> approx. 12 times as slow as theoretically  (100Mbps / 8= 12 Mb/s)
    JC> possible! I've benchmarked from inside and outside the network;
 inside I JC> get 1Mb/s max and outside 300kb/s. Tried various protocols,
 such as ssh, JC> smb and http, each with similar results.
    JC>
    JC> What can I do to pinpoint the bottleneck?
    JC>

 I suspect you are having the full vs half duplex problem. 

It says:
"A common source of LAN trouble with 100BT networks is that the host is set to 
full duplex, but the Ethernet switch is set to half-duplex, or visa versa.
Most newer hardware will auto-negotiate this, but with some older hardware, 
auto-negotiation sometimes fails. result is a working but very slow network 
(typically only 1-2 Mbps). Best for both to be in full duplex if possible, 
but some older 100BT equipment only supports half-duplex."

ifconfig should give you the information whether autoselect is enabled and if 
the network is running at full or half duplex.

Regards
Bhaskar.

- -- 

_______________________________

 Bhaskar Dutta  <bhaskie99 at yahoo.co.uk>
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