[PLUG] Troubleshooting DHCP...

Mike Connors mconnors1 at gmail.com
Mon Dec 28 09:46:17 UTC 2009


Michael Robinson wrote:I tried to replace
> the Dlink hub with a Netgear DSS5+ 5 port switch.  I guess my switch is
> faulty.  It seems unlikely that the cables themselves didn't handle
> 100BaseTX transmission okay.  Obviously there was some networking from
> the diskless client to the server at 100BaseTX, but somehow the switch
> broke DHCP.  Put the slow dumb hub back in, works just fine.  
>   
It is possible that the switch is faulty, however my experience with
auto-negotiation is that each vendor (hub, switch, network card)
interpret and implement the N-WAY standards differently.

Does the D-Link hub support auto-negotiation? That could explain why
the hub works and the switch doesn't. If the hub doesn't support 
auto-neg then
both ends of the connection will fall back to 10mbps half-dup and all is 
well.

If auto-negotiation isn't configured the same on both the switch port
and NIC then there will be duplex mismatch errors.

A telltale sign of duplex mismatch is Ethernet errors such as
Frame Check Sequence errors, late collisions, and runts.

You can use  the 'ethtool' command to look at Ethernet interface error 
counters.




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