Half or Full Duplex

[Kevin McKie]

I am trying to set our LAN card to be 10mbs Full Duplex, from it's current Half Duplex state, but don't know how, any info would be much appreciated.

[Jeff Schussele · Accepted solution]

Hi,

10MB by design is half-duplex *only*. Full duplex is only supported on 100MB & up.
So if the card is 10MB only, then you're stuck with half duplex.

Rgds,
Jeff

[Helen French]

You cannot have full duplex setting on a 10mbps card. You can only set it on the 100mbps card and above.

But if you have 100mbps, then use "lanadmin" command to change these options:

# man lanadmin

or use SAM.

[Kevin McKie]

Thank you, info much appreciated. I don't know how we get round this now as we are getting lots of collisions on our 100mb switch, even when the port in question is set to 10 half duplex. Networks theory is that because every other piece in the network is set to 100mb, the 10mb card in the HP must be getting over loaded, although I can't see any errors looking at lanadmin.

[Hai Nguyen_1]

Kevin,

Try SAM to set it to full duplex. SAM > Networking and Communications > Network Interface Cards. Then select the card you want to change the duplex setting. From this point on, the scren info should be easy to follow.

Hai

[Jeff Schussele]

Hi Kevin,

Unfortunately collisions are a fact of life in half duplex comm. But the collisions will only be between the NIC & the switch. Think of it as two people starting to talk at the same time. Both have to pause & try again. Not destructive mind you, just slows the conversation down.

Rgds,
Jeff

[Ron Kinner]

What exactly is a lot of collisions? You need to look at it as a percentage of total packets sent. Half duplex is going to have collisions. They are expected and usually dealt with fairly well without really hurting anything.

That being said I have seen problems with a 10 half connection to a router when one heavy hitter was on 100 full and the rest on 10 half. The 100 full machine was able to monopolize the router's input queues so that other processes timed out. You might want to invest in a new card if you are seeing performance issues.

Ron

[Todd Whitcher]

Hi,

The setting of speed and duplex depends on the type of card you have, most HP interfaces can do 10 HD/FD 100HD FD or auto. The switch has to support this also.


To see what type of card you have run an ioscan.

ioscan -fnC lan

Look at the driver for the card, here are common HP Interface cards and their config files, you can set the speed & duplex in the config file and via the lanadmin command.

A quick way to tell if your card supports full duplex is to run lanadmin:

lanadmin -X 10FD PPA# /NMID #( for 11.X lan0 = ppa0 lan1 = ppa1 etc. for 10.20 use the nmid value from lanscan )

e.x. 11.X
lanadmin -X 10FD 0 ( for lan 0 )

Check if you have one of these drivers, the config files are in /etc/rc.config.d/

btlan0 hpeisabtconf
btlan1 hpbasetconf
btlan3 hpbase100conf
btlan4 hpgsc100conf
btlan5 hppci100conf
btlan6 hpsppci100conf
intl100 hpintl100conf
btlan hpbtlanconf

Example entries, the description for each card is in the header of the file.

xxx_INTERFACE_NAME : Name of interface (lan0, lan1...)

xxx_STATION_ADDRESS : Station address of interface. This will be the MAC address of your interface.

xxx_SPEED : set the card speed. Value are : 10HD, 10FD,100HD, 100FD, auto_on.

Collisions are a fact of life w/ half duplex, see this link for tons of ethernet info.

http://www.ethermanage.com/ethernet/ethernet.html

Cheers

Todd