Discussion:
half duplex
(too old to reply)
larinia
2005-07-29 07:57:12 UTC
Permalink
Hello list,

I am running debian unstable version on my laptop, for some reason, the
eth0 is running under half duplex. The interface does come up and I do
have internet access, I am just wondering if there is a way I can make
it working under full duplex. Can anyone help?

Thanks a lot

Larinia
Doofus
2005-07-29 08:37:38 UTC
Permalink
Post by larinia
Hello list,
I am running debian unstable version on my laptop, for some reason,
the eth0 is running under half duplex. The interface does come up and
I do have internet access, I am just wondering if there is a way I can
make it working under full duplex. Can anyone help?
Thanks a lot
Larinia
Hello.
How do you know you're running at half duplex?
What's the other end of your cat-5 cable connected to?
larinia
2005-07-29 10:51:23 UTC
Permalink
Hello,

I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
then it is connecting to a hub, which is then connect to a wireless bridge.
Post by Doofus
Post by larinia
Hello list,
I am running debian unstable version on my laptop, for some reason,
the eth0 is running under half duplex. The interface does come up and
I do have internet access, I am just wondering if there is a way I
can make it working under full duplex. Can anyone help?
Thanks a lot
Larinia
Hello.
How do you know you're running at half duplex?
What's the other end of your cat-5 cable connected to?
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Modestas Vainius
2005-07-29 11:31:12 UTC
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Post by larinia
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
then it is connecting to a hub, which is then connect to a wireless bridge.
If the other end is a hub, it may not be capable of doing full-dupex, so both
ends autonegiotiated the half-duplex mode (both ends must run in the same
(either full or half) duplex). AFAIK, linux defaults to full-duplex whether
possible. Nevertheless, there is nothing wrong with half-duplex, it's just
the way signals are sent over a wire. You don't need to worry about this.
Patrick Dreker
2005-07-29 11:16:55 UTC
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Post by larinia
then it is connecting to a hub, which is then connect to a wireless bridge
If the other device really is a hub, then half-duplex is the best you'll get.
Only switches can do full duplex...

Patrick
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Nick Leverton
2005-07-29 11:46:54 UTC
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Post by larinia
Hello,
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
then it is connecting to a hub, which is then connect to a wireless bridge.
Run "mii-tool -v" and see what it says. It doesn't work on all network
adaptors, I'm especially unsure about the embedded type you get in
laptops.

But if it works, the "link partner" line will tell you whether the
hub can do full-duplex, and if you paste the output here we can see if
there's anything wrong.

Please either keep debian-kde in or CC me directly, thank you
Nick
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Vincent Bernat
2005-07-29 13:41:35 UTC
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OoO Peu avant le début de l'après-midi du vendredi 29 juillet 2005,
Post by Nick Leverton
Post by larinia
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
then it is connecting to a hub, which is then connect to a wireless bridge.
Run "mii-tool -v" and see what it says. It doesn't work on all network
adaptors, I'm especially unsure about the embedded type you get in
laptops.
On adapters that don't work, ethtool may work.
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Dietz Proepper
2005-07-29 11:45:00 UTC
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Post by larinia
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
It is.
Post by larinia
then it is connecting to a hub, which is then connect to a wireless bridge.
That's the point. A hub can only give you a half duplex connection as
opposed to a switch. For an explanation see [1]. But it should not matter
in your setup cause the wireless bridge will be the bottleneck anyway.

[1] i.e. http://www.duxcw.com/faq/network/hubsw.htm
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larinia
2005-07-29 12:22:33 UTC
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ehm, thank you all very much, I will try to connect my laptop directly
with the modem and see if there is any difference.

Does half duplex make the network traffic slower?
Post by Dietz Proepper
Post by larinia
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
It is.
Post by larinia
then it is connecting to a hub, which is then connect to a wireless bridge.
That's the point. A hub can only give you a half duplex connection as
opposed to a switch. For an explanation see [1]. But it should not matter
in your setup cause the wireless bridge will be the bottleneck anyway.
[1] i.e. http://www.duxcw.com/faq/network/hubsw.htm
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Dietz Proepper
2005-07-29 14:31:05 UTC
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Post by larinia
ehm, thank you all very much, I will try to connect my laptop directly
with the modem and see if there is any difference.
You need another cable (or a rather intelligent nic or modem;) for this.
Post by larinia
Does half duplex make the network traffic slower?
It does. But as I already said, this should not matter in your situation,
because that bridge (or modem or whatever) will be the bottleneck.
Therefore, simply leave it as it is.
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Lei Yu
2005-07-29 21:13:41 UTC
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I have done "mii-tool -v", here is the outcome

eth0: negotiated 100baseTx-HD, link ok
product info: vendor 00:40:63, model 50 rev 8
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
link partner: 100baseTx-HD 10baseT-HD

I think the hub does support full duplex. It is netgear dual speed hub model
DS104.
Post by Dietz Proepper
Post by larinia
ehm, thank you all very much, I will try to connect my laptop directly
with the modem and see if there is any difference.
You need another cable (or a rather intelligent nic or modem;) for this.
Post by larinia
Does half duplex make the network traffic slower?
It does. But as I already said, this should not matter in your situation,
because that bridge (or modem or whatever) will be the bottleneck.
Therefore, simply leave it as it is.
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Nick Leverton
2005-07-29 22:10:18 UTC
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Post by Lei Yu
I have done "mii-tool -v", here is the outcome
*snips*
Post by Lei Yu
link partner: 100baseTx-HD 10baseT-HD
I think the hub does support full duplex. It is netgear dual speed hub model
DS104.
The hub is telling your eth0 that it doesn't - only half duplex (HD),
at 100 Mbits or 10 Mbits. To find out if it actually does FD, you can
try forcing full duplex temporarily with "mii-tool -F 100baseTx-FD eth0".
Watch the output from "ifconfig eth0" to see if the Errors or Collisions
start going wild, which will indicate that the hub doesn't do full duplex.

Having said that, Amazon have the manual online, linked in from
http://www.amazon.com/exec/obidos/tg/detail/-/B00000J4LQ/002-4342910-3697617?v=glance
and the Troubleshooting section says to ensure the conected PC is set
to half dulpex, so it looks like the hub is only HD I'm afraid.

Regrets,

Nick
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larinia
2005-07-29 22:43:16 UTC
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Thanks a lot for your help. :-)
Post by Nick Leverton
Post by Lei Yu
I have done "mii-tool -v", here is the outcome
*snips*
Post by Lei Yu
link partner: 100baseTx-HD 10baseT-HD
I think the hub does support full duplex. It is netgear dual speed hub model
DS104.
The hub is telling your eth0 that it doesn't - only half duplex (HD),
at 100 Mbits or 10 Mbits. To find out if it actually does FD, you can
try forcing full duplex temporarily with "mii-tool -F 100baseTx-FD eth0".
Watch the output from "ifconfig eth0" to see if the Errors or Collisions
start going wild, which will indicate that the hub doesn't do full duplex.
Having said that, Amazon have the manual online, linked in from
http://www.amazon.com/exec/obidos/tg/detail/-/B00000J4LQ/002-4342910-3697617?v=glance
and the Troubleshooting section says to ensure the conected PC is set
to half dulpex, so it looks like the hub is only HD I'm afraid.
Regrets,
Nick
Dietz Proepper
2005-07-30 11:51:54 UTC
Permalink
Post by Nick Leverton
Post by Lei Yu
I think the hub does support full duplex. It is netgear dual speed hub
model DS104.
The hub is telling your eth0 that it doesn't - only half duplex (HD),
at 100 Mbits or 10 Mbits. To find out if it actually does FD, you can
try forcing full duplex temporarily with "mii-tool -F 100baseTx-FD
eth0". Watch the output from "ifconfig eth0" to see if the Errors or
Collisions start going wild, which will indicate that the hub doesn't do
full duplex.
Sorry to say this again - if it's a HUB it will never - never - never
support FD. Hubs generally only support HD links due to their design.

Switchs can and normally do support FD.

But this does not matter normally, the slowdown is acceptable, at least for
SOHO and smaller kinds of setups.
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Jeff Coppock
2005-08-02 20:45:20 UTC
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Post by Lei Yu
I think the hub does support full duplex. It is netgear dual speed hub
model DS104.
These "dual-speed" hubs are still hubs. They simply provide a single
switch (bridge) between the 10Mbps and the 100Mbps segments. Essentially,
it combines a 10Mbps hub and a 100Mbps hub into a single unit and then a
switch circuit connects the two.

So, being a hub (repeater), only half duplex is supported.

jc
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Paul Johnson
2005-08-03 04:50:58 UTC
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Post by Jeff Coppock
Post by Lei Yu
I think the hub does support full duplex. It is netgear dual
speed hub model DS104.
These "dual-speed" hubs are still hubs. They simply provide a
single switch (bridge) between the 10Mbps and the 100Mbps segments.
Essentially, it combines a 10Mbps hub and a 100Mbps hub into a
single unit and then a switch circuit connects the two.
Aren't home-user oriented dual-speed ethernet devices typically
implemented in the form of a switch?
Jeff Coppock
2005-08-03 20:17:54 UTC
Permalink
Post by Paul Johnson
Post by Jeff Coppock
Post by Lei Yu
I think the hub does support full duplex. It is netgear dual
speed hub model DS104.
These "dual-speed" hubs are still hubs. They simply provide a
single switch (bridge) between the 10Mbps and the 100Mbps segments.
Essentially, it combines a 10Mbps hub and a 100Mbps hub into a
single unit and then a switch circuit connects the two.
Aren't home-user oriented dual-speed ethernet devices typically
implemented in the form of a switch?
Not from what I see. But both are available, you're just gonna pay more
for a "switch" than for a "hub" since there is more circuitry in the switch.

If the dual-speed ethernet device says "hub", each unit has a built-in
self-learning bridge which provides the communications link between the 10
and 100 Mbps network devices. The intelligent bridge automatically manages
network traffic such that 100 Mbps traffic does not unnecessarily crowd the
10 Mbps network segment and 10 Mbps traffic does not crowd the 100 Mbps
segment.

If the dual-speed ethernet device says "switch", then each port is bridged
individually, so each port supports both HD and FD.

jc
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Doofus
2005-07-29 12:34:44 UTC
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Post by larinia
Hello,
I saw the half duplex message in the /var/log/syslog. I am not sure if
the cat-5 cable is the network cable(Sorry, I am a newbie), if it is,
then it is connecting to a hub, which is then connect to a wireless bridge.
Post by Doofus
Post by larinia
Hello list,
I am running debian unstable version on my laptop, for some reason,
the eth0 is running under half duplex. The interface does come up
and I do have internet access, I am just wondering if there is a way
I can make it working under full duplex. Can anyone help?
Thanks a lot
Larinia
Hello.
How do you know you're running at half duplex?
What's the other end of your cat-5 cable connected to?
Tell us the make and model of your hub and maybe we can quickly find out
if it'll talk duplex. Generally speaking you need a proper ethernet switch.

There are quite a few instances of some switch gear being incompatible
with some network interfaces when relying on Auto N-way. Cisco and Sun
HappyMeals probably the best example. In these cases you need to have
only one of the two running auto-negotiation and the other hard set to
run 100MB/FD.
phyrster
2005-07-29 11:22:20 UTC
Permalink
Post by larinia
Hello list,
I am running debian unstable version on my laptop, for some reason, the
eth0 is running under half duplex. The interface does come up and I do
have internet access, I am just wondering if there is a way I can make
it working under full duplex. Can anyone help?
The simple way to know whether you are using half-duplex or not is run:

ethtool

you can use it to change NIC's mode.

I deliberately changed mine into half-duplex/10M because if it is
100M/duplex, the connection is very slow with my pppoe link.

Don't worry too much if you are using a 10M network anyway.

regards

bxuef

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larinia
2005-08-09 08:59:50 UTC
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Thank you everyone, you've been great help to me!
Post by phyrster
Post by larinia
Hello list,
I am running debian unstable version on my laptop, for some reason, the
eth0 is running under half duplex. The interface does come up and I do
have internet access, I am just wondering if there is a way I can make
it working under full duplex. Can anyone help?
ethtool
you can use it to change NIC's mode.
I deliberately changed mine into half-duplex/10M because if it is
100M/duplex, the connection is very slow with my pppoe link.
Don't worry too much if you are using a 10M network anyway.
regards
bxuef
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will gather well taught aphorisms (dhammapadas), like an connoisseur
picking a flower? 44
A disciple will master this world and the world of Death with its devas.
A disciple will gather well taught aphorisms (dhammapadas), like a
connoisseur picking a flower. 45
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