Date: Tue, 22 Feb 2000 20:44:16 -0700 From: Wes Peters <wes@softweyr.com> To: Lloyd Rennie <lloyd@vbc.net> Cc: Wim Livens <livensw@rc.bel.alcatel.be>, Yusuf Goolamabbas <yusufg@outblaze.com>, freebsd-net@freebsd.org Subject: Re: Understanding ifconfig output Message-ID: <38B35790.EA9CADF@softweyr.com> References: <Pine.BSF.4.05.10002211533070.63343-100000@brunel.uk1.vbc.net>
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Lloyd Rennie wrote:
>
> On Mon, 21 Feb 2000, Wim Livens wrote:
>
> > On Mon, Feb 21, 2000 at 11:35:04AM -0000, Yusuf Goolamabbas wrote:
> > > Here's some sample output from one of my machines (3.4-stable) which
> > > has an Intel EEPro 100 attached to a Bay 350 switch
> > >
> > > fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> > > <ip address deleted>
> > > ether 00:90:27:8d:49:7b
> > > media: autoselect (100baseTX <full-duplex>) status: active
> > ^^^^^^^^^^^^^^^^^^^^^^^
> > This is the info you want---^
> >
> > I don't know what SIMPLEX means, I use the same card in 100Mb
> > full-duplex and get similar output.
>
> Same here. The media autoselects FD, but still the simplex flag is set.
> *shrug*
They have completely different meanings. A quick look at the ifconfig
source would tell you that. The 'flags=8843<...>' part of the output
is the network interface options; IFF_SIMPLEX and friends are defined in
/usr/include/net/if.h:
...
#define IFF_ALLMULTI 0x200 /* receive all multicast packets */
#define IFF_OACTIVE 0x400 /* transmission in progress */
#define IFF_SIMPLEX 0x800 /* can't hear own transmissions */
#define IFF_LINK0 0x1000 /* per link layer defined bit */
...
As you can see, the IFF_SIMPLEX flags means this interface cannot hear it's
own transmissions.
Later, the media options are printed, showing you that your network interface
card is configured for 100Base-TX full-duplex.
> > What is the recommended way to determine link speed from a machine to
> > a hub/switch. (e.g A colo provider claims that there is 100 Mbit card
> > in the box and one would want to verify that)
>
> A fairly foolproof method is to make sure there's a fair amount of traffic
> running in both directions, then do a 'netstat -I fxp0 -w1'. Watch the
> collisions - if you see any then it's not FD.
For the link speed, just look at the ifconfig output. If the interface is
set to 100Base-TX and is working, it's in 100 Mbps mode. The only other
option is 10Base-T. 100Base-TX full duplex is actually 200 Mbps - 100 each
way.
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
wes@softweyr.com http://softweyr.com/
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