[CentOS] Need help with an odd issue I am experiencing

RobertH roberth at abbacomm.net
Tue Sep 9 14:30:30 UTC 2008


> 
> I have a server with dual nic's running centos 5.2 1 nic connects to the
> cable modem, which has 15m d and 2m up, but speed tests barely come back
> at 5mb down including road runner's internal speed test. I hook up my
> laptop to the same modem, same port, using the same cable and I get 17mb
> down. I have ruled out iptables, nics (because same result on both
> nics), cables, cable modem(with a brighthouse rep) any suggestions would
> be greatly appreciated. Thanks.
> 

David,

IME, it is typically (yet not always) a duplex and/or speed issue between
the NIC port and the switch or device it is talking too.

man ethtool

ethtool eth0

and check to see what speed and duplex are currently in use...

if duplex and/or speed are off I typically hard code a *managed* switch and
the centos box on whatever ports as necessary by adding this line or one
similar to it

ETHTOOL_OPTS="speed 100 duplex full autoneg off"

To this and other interface files as necessary

/etc/sysconfig/network-scripts/ifcfg-eth0

At this point a reboot will take care of it or if you don't want to reboot
now, Then I would make a little script called downup.sh

ifdown eth0
ifup eth0

and then I chmod 750 that script and then call it like this if from remote

./downup.sh &

So I don't lose connectivity...

There is probably a more elegant command like way to do that...

Be careful if remote box and YMMV

 - rh




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