What is alt0 on SCO OpenServer(TM) Release 5?

What is atl0, and is it always supposed to be present?

At some of our locations, ifconfig -a produces this:
net0: flags=4043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1343
        inet 10.1.13.2 netmask ffffff00 broadcast 10.1.13.255
        perf. params: recv size: 24576; send size: 24576; full-size frames: 1
        ether 00:12:79:55:76:b9
lo0: flags=4049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 8232
        inet 127.0.0.1 netmask ff000000
        perf. params: recv size: 57344; send size: 57344; full-size frames: 1
atl0: flags=404a<BROADCAST,LOOPBACK,RUNNING,MULTICAST> mtu 8232
        inet 0.0.0.0 netmask ff000000
        perf. params: recv size: 4096; send size: 8192; full-size frames: 1

However, at one location it only shows:
net0: flags=4043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1180
        inet 10.1.9.2 netmask ffffff00 broadcast 10.1.9.255
        perf. params: recv size: 24576; send size: 24576; full-size frames: 1
        ether 00:18:71:fc:f6:30
lo0: flags=4049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 8232
        inet 127.0.0.1 netmask ff000000
        perf. params: recv size: 57344; send size: 57344; full-size frames: 1

Coincidentally, this is the location at which I have to keep MTU lower than at the others, due to fragmentation issues.

What is atl0 and what does it do?
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MashaCPAAsked:
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mikelfritzCommented:
From:

http://aplawrence.com/Bofcusm/260.html

> >From searching the man pages and the SCO site, the only information
> I could gather about the atl0 interface is that it is some kind of
> "binding post" for IP aliases.

And:

http://aplawrence.com/Bofcusm/376.html

It looks to have to do with virtual domains.  all of the SCO boxes I've looked at have the atl0 interface, but I see some posts with servers that do not.  Maybe this is not even the problem.

What kind of network card is it?  hwconfig and/or netconfig
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MashaCPAAuthor Commented:
# hwconfig
name=kernel vec=- dma=- rel=3.2v5.0.7 kid=2003-02-18
name=cpu vec=- dma=- unit=1 family=15
name=cpuid vec=- dma=- unit=1 vend=GenuineIntel tfms=0:15:4:10(0)
name=fpu vec=13 dma=- unit=1 type=80387-compatible
name=pci base=0xCF8 offset=0x7 vec=- dma=- am=1 sc=1 buses=14
name=PnP vec=- dma=- nodes=0
name=clock vec=- dma=- type=TSC/3.000107388Ghz
name=serial base=0x3F8 offset=0x7 vec=4 dma=- unit=0 type=Standard nports=1 base
=0 16550A/16
name=serial base=0x2F8 offset=0x7 vec=3 dma=- unit=1 type=Standard nports=1 base
=8 16550A/16
name=console vec=- dma=- unit=vga type=0 num=12 scoansi=1 scroll=50
name=floppy base=0x3F2 offset=0x5 vec=6 dma=2 unit=0 type=135ds18
name=parallel base=0x378 offset=0x2 vec=7 dma=- unit=0
name=udi vec=- dma=- UDI environment
name=adapter vec=- dma=- ha=0 type=usb_msto UDI SCSI HBA
name=adapter base=0x1F0 offset=0x7 vec=14 dma=- type=IDE ctlr=0 dvr=wd
name=cled vec=- dma=- Compaq ProLiant Storage System (rev 5.74a)
name=pcibios vec=- dma=- PCI BIOS (3.0), Hardware Mechanism 1
name=cevt vec=- dma=- hp ProLiant Event Logging Driver (rev 5.74a)
name=adapter base=0x4000 offset=0x80 vec=10 dma=- type=lsil ha=0 id=7 Chip=1030
10409
name=casm base=0x2800 offset=0xFF vec=11 dma=- hp ProLiant Advanced Server Manag
ement Driver (rev 5.74a)
name=bcme0 vec=10 dma=- chip=BCM5721 mem=FDEF0000 addr=00:18:71:fc:f6:30
name=cd-rom vec=- dma=- type=IDE ctlr=0 cfg=mst unit=0 dvr=Srom->wd
name=tape vec=- dma=- type=S ha=0 id=2 lun=0 bus=0 ht=lsil unit=0
name=disk vec=- dma=- type=S ha=0 id=0 lun=0 bus=0 ht=lsil unit=0
name=Sdsk vec=- dma=- cyls=8855 hds=255 secs=63 unit=0 fts=stdb
name=Sdsk-0 vec=- dma=- Vnd=COMPAQ Prd=BF07289BC4 Rev=HPB1
name=usb_ehci vec=5 dma=- PCI bus=0 dev=29 func=7
name=usb_uhci vec=5 dma=- PCI bus=0 dev=29 func=0
name=usb_uhci vec=5 dma=- PCI bus=0 dev=29 func=1
name=usb_uhci vec=5 dma=- PCI bus=0 dev=29 func=2
name=usb_uhci vec=5 dma=- PCI bus=0 dev=29 func=3
name=usb_uhci vec=11 dma=- PCI bus=1 dev=4 func=4
name=Stp-0 vec=- dma=- Vnd=HP Prd=C7438A Rev=ZP5A

Maybe this atl0 is completely unrelated to the problem - I just want to make sure that there is nothing wrong in not having it.
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mikelfritzCommented:
I doubt that is the problem.  Maybe and updated driver would help, or possibly some system suplements need to be applied...

What release of Openserver 5 is it?  "uname -a"

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MashaCPAAuthor Commented:
SCO_SV
3.2 5.0.7 i386
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gemartiCommented:
Does your systems reporting the atl0 interface have modems?

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gemartiCommented:
The reason I ask is because modems use
atl0 = attention Linefeed off
atl1 = attention Linefeed on

since atl0 is reporting an ip address of 0.0.0.0 netmask ff00000 it is in active (i.e. Linefeed off).

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mikelfritzCommented:
Here is a driver that may be newer than what you have loaded:

http://www.sco.com/support/update/download/release.php?rid=387

What symptoms are you seeing?

Is this a new problem or has this server always had problems?
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