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List:       tru64-unix-managers
Subject:    SUMMARY: SLIP: ifconfig is frozen! (additional SUMMARY)
From:       Winfried Huber <win () tukan ! ffb ! eunet ! de>
Date:       1995-12-27 16:18:46
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Hi there,
  this is an additional summary for the ifconfig/SLIP problem. It
contains a significant enhancement of the final summary I posted at
Dec, 22.

--- new part begins here ---

Eric Baur <ecb@ventoux> pointed out that it is *not* possible to
simply reconfigure the SLIP interface. Shutting it down and killing
slattach and clearing the default route is not enough. What you have
to do is to explicitely *delete* the old interface address before you
can assign a new one:

  ifconfig sl0 delete <address>

It is *not* possible to overwrite the old address, you have to clear
it first and then you are allowed to enter a new address pair.

I checked it out and found this works (at least sometimes, maybe I am
going to become superstitious). Thanks, Eric!

I was thinking the delete command is used to remove an incorrectly
specified alias, or to remove it if it is no longer needed. At least
this is what man ifconfig claims!

--- new part ends here, this is the rest of the "final summary": ---

The first answer told me to discard SLIP and switch to PPP instead
(thanks, Sharma, Tushar (tsharma@dialcall.com)). Installing it is a
children's game, and it works really great! If at all possible I
recommend everyone to install it.

PPP V2.2 (Steve Tate's implementation) can be found at 
ftp://zaphod.csci.unt.edu/pub.

It comes with chat, which takes care of dialing the modem an logging
in into the remote system, so a one line command is enough to start the
internet connectivity!

Though my problem was solved by PPP, I tried to make SLIP work on two
different networks.

Some guys asked me if I really did "ifconfig sl0 down" and kill the
slattach. Of course, I did. And I did "route flush".

Hellebo Knut <Knut.Hellebo@nho.hydro.com> told me to check the alias
mechanism, thus configuring the sl0 interface with two different
addresses, and to add multiple search domains to /etc/resolv.conf.

This did not work for me. I believe the problem is that it *is*
possible to *receive* packets sended to a second address by using the
"alias" mechanism of ifconfig; this is for switching to a different
network while still beeing able to receive packets sended to the old
address. 

But I can't reconfigure the sl0 interface, so this does not help. The
problem, as I see it (but I am not sure whether this is correct),
seems to be that I don't only want to receive packets via the
reconfigured address, what I need is to send packets via the
reconfigured address, too. And this seems to be impossible without
completely reconfiguring the sl0 via ifconfig, which is what failed.
So my packet actually was sended via the modem (I see the LEDs blink),
but the other host discarded the packets as they seemed to come from
the wrong sender. Hope this understanding is not completely wrong...

So, if at all possible, get and install PPP and condolence to all who
can't switch to PPP because they can't convince the machine at the
other end to use PPP, too.

Thanks to

"Sharma, Tushar" <tsharma@dialcall.com>
Jim Wright <jwright@phy.ucsf.edu>
Hellebo Knut <Knut.Hellebo@nho.hydro.com>

-Winfried

-- original posting follows here:

-> Arghhh .... hi there, oh gurus in the net ...
-> 
->   got a problem: I need to connect my machine via SLIP alternating to
-> two different service providers to get two different flavours of
-> internet access. So I need to switch between two different SLIP
-> setups:
-> 
-> Provider 1 (eunet):
-> 	   ifconfig sl0 193.96.78.4 193.96.76.1
-> 	   route add default 193.96.76.1
-> 
-> - and -
-> 
-> Provider 2 (xlink):
-> 	   ifconfig sl0 193.141.69.186 193.141.69.1
-> 	   route add default 193.141.69.1
-> 
-> As I understand the docs it should be possible to reconfigure the slip
-> interface using the ifconfig command, but then a restart of the
-> internet services (/usr/sbin/rcinet restart) is necessary to notify
-> all daemons of the changes.
-> 
-> But it doesn't work! I can't manage to reconfigure the slip interface
-> regardless of stopping or restarting the internet services! Even
-> running "netsetup" doesn't help! I have to reboot the machine to get
-> the patches to work.
-> 
-> I flushed the static routing table (/sbin/route flush) and made sure
-> all slattach's are killed, and everything other I could think of. It
-> seems the setup of the slip interface is "frozen by an ice monster":
-> 
-> tukan#413# ifconfig sl0
-> sl0: flags=10<POINTOPOINT>
-> 	inet 193.96.78.4 --> 193.96.76.1 netmask ffffff00  ipmtu 296 
-> tukan#414# ifconfig sl0 193.141.69.186 193.141.69.1 ; ifconfig sl0
-> sl0: flags=11<UP,POINTOPOINT>
-> 	inet 193.96.78.4 --> 193.96.76.1 netmask ffffff00  ipmtu 296 
-> 	     ===========================
-> 	     this are the previous values, changes didn't work!
-> 
-> Why didn't "ifconfig sl0 193.141.69.186 193.141.69.1" redefine the
-> addresses of the slip interface sl0???
-> 
-> Some additional info:
-> DEC 3000 300X AXP running OSF1 2.0
-> 
-> tukan[314]> uname -a
-> OSF1 tukan.ffb.eunet.de V2.0 240 alpha
-> 
-> I configured my machine as a master bind server with forwards to the
-> external name servers of the service providers.
-> 
-> Everything works fine in the initial setup with eunet (DNS, mail, ftp,
-> www, everything works fine with eunet), and if I patch the initial
-> setup to xlink *and reboot* everything works fine for xlink.
-> 
-> But I can't manage to switch between the two configurations without
-> rebooting. My first guess was to use sl0 for eunet and sl1 for xlink,
-> but this seems not to be possible as I have only one serial port and
-> one modem (well, one fine working modem).
-> 
-> Any clue? Am I too dull to RTFM? I tried and studied for days...
-> 
-> As usual, I will summarize.
-> 
-> TIA,
-> Winfried
-> 
-> -- 
-> Winfried Huber, Softwarehaus Huber & Boehm,	voice: +49 8142 13038
-> Illerweg 6, D-82140 Olching, Germany		fax:   +49 8142 18612
-> win@tukan.ffb.eunet.de
-> 

------- End of forwarded message -------

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