What is atl0?

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Kevin Lentin

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Jan 5, 1998, 3:00:00 AM1/5/98
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I have a network device called atl0 configured. I can't find who is running
ifconfig to create it and so far I can't even locate the thing in the
kernel drivers. It's sitting with an IP of 0.0.0.0 and a netmask of
127.0.0.0 which is very illegal.

Anybody know what it is, where it comes from, what creates it, what it does
and is it contributing to my network nightmare?

BTW The nightmare is that for some reason no routes are showing up at boot
time. If I re-ifconfig the interface, they turn up. I'll experiment his
evening on this half of the problem before posting details.

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Bela Lubkin

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Jan 6, 1998, 3:00:00 AM1/6/98
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Kevin Lentin wrote:

> I have a network device called atl0 configured. I can't find who is running
> ifconfig to create it and so far I can't even locate the thing in the
> kernel drivers. It's sitting with an IP of 0.0.0.0 and a netmask of
> 127.0.0.0 which is very illegal.
>
> Anybody know what it is, where it comes from, what creates it, what it does
> and is it contributing to my network nightmare?

See /etc/rc2.d/S90atlas, /etc/strcf.d/11atl. (Note that there are two
ways it gets set up -- the normal way, or if "ksl.disable" was specified
at the boot prompt, which would be quite unusual; don't get confused.)

"atl0" interface was introduced by the Internet FastStart stuff (SCO
Internet FastStart 1.0.0, 1.1.0, and then incorporated into OSR5.0.4).
Internally it is a second device running over the loopback interface,
same as "lo0". Its serves as an interface to which aliases can be
assigned, i.e. if you are using Internet FastStart's multi-IP
facilities. I believe it automatically adds "atl1" etc. if you need
more than 256 aliases.

The insane and probably illegal netmask of both lo0 and atl0 is a known
issue. It isn't known to actually cause any problems; it's just a weird
number.

At kernel relink time, /etc/strcf.d/* are mashed into an internal format
which can be used by the "ksl" (kernel STREAMS linker) driver. If you
change /etc/strcf.d/11atl, you need to relink the kernel to enact the
changes. See also slink(ADMN), strcf(SFF).

> BTW The nightmare is that for some reason no routes are showing up at boot
> time. If I re-ifconfig the interface, they turn up. I'll experiment his
> evening on this half of the problem before posting details.

Well, I doubt atl0 has anything to do with this problem.

OSR5 includes at least three routing daemons: routed, gated, and irdd.
Which, if any, are you running? routed & gated have "-t" options to
turn on tracing; irdd had a "-d" debug flag. Turn on the appropriate
one(s) in /etc/tcp (which should be linked with /etc/rc2.d/S85tcp). By
what mechanism are routes *supposed* to be turning up?

>Bela<

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