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References: <20041201204549-40138-8@molen>
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Date:  Thu, 02 Dec 2004 21:35:37 +0100
Sender: os2-wireless_users-owner <os2-wireless_users-owner@2rosenthals.com>
Reply-To: os2-wireless_users@2rosenthals.com
From:  Christian Langanke <os2-wireless_users@2rosenthals.com>
To:  os2-wireless_users@2rosenthals.com
Subject: [OS2Wireless] Wireless LAN Monitor

Peter Verweij wrote:

>True, but then I have to use DHCP which I don use. 
>
Ok, if you don't use DHCP, things are even easier. You will possibly 
like to hear that the upcoming version of XWLAN will extend manually IP 
setup by configuration of a default gateway and DNS service (I did that 
just yesterday).

>True, but I have a strange problem with one workaround.
>Normally wireless lan is on 192.168.1.18 and wired lan is on 192.168.3.19 (not used)
>When I want to backup I change wireless to 192.168.2.18 and wired tot 192.168.1.19.  
>
AFAIU you set the IP configuration in the connection profile to "don't 
configre" and do IP configuration of both the wireless and the wired 
interface with the script. Ahem... if that is the case, at least 
concerning the configuration of the wireless interface this is not what 
was intended with the script feature. You may understand that I invested 
a lot of time in automating this part and certainly would like to 
concentrate on fixing bugs there rather in scripts of users :-(

I would more than recommend to let XWLAN configure the wired IP 
interface, and to configure the wired interface in the scripts unless 
that is not implemented in XWLAN or any other solution.

On the disconnect event on XWLAN I would completely delete the IP 
interface that is not used, as there is no use in having an interface 
being configured to an unused IP subnet. This is exactly what XWLAN 
does, if you select "manual configuration" and enter an IP address for 
the wireless interface: on disconnect it executes "ifconfig lanx delete" 
for the interface bound to the Wifi driver. You should do that as well 
with the wired interface on the XWLAN connect event,
followed by an ARP flush (execute "arp -f", see below).

So if you use the XWLAN scripts to setup  any TCP/IP configuration, you 
would configure / unconfigure the _wired _interface there _only_, and 
unconfiguration would mean "ifconfig lanx _delete_". Leave the 
onfiguration of the wireless interface to XWLAN, that is what it was 
made for.

>But when I keep the wireless radio on I get an problem after 1 or 2 hours, The notebook isn't reachable anymore. I think it has to do with the accesspoint 
>which work on 192.168.1.7 and 192.168.1.17 (maybe a routing problem or something else).
>
I would think it is an ARP problem, which holds the built-in MAC 
addresses of a NIC. Once this table is flushed, IP connections built up 
after the change from wireless to wired will let the TCP/IP stack use 
the routes of the new connection, as the old ARP entries are not longer 
available. In other words, not flushing the ARP cache may lead to 
problems, either right away or later.

This is why XWLAN flushes the arp table on a disconnect event. And it 
does so on your system as well if you let it configure (and so 
unconfigure) the wired interface (as well). As said above, this makes 
also sense when switching from wired to wireless, so you better flush 
the ARP cache as well when deleting the wired interface. It may well be 
that disableing the radio also works around the error, but I would think 
that obsolete ARP entries are the error source.

If the error persists, I would like to know if a manually "arp -f" 
executed in an eCS window solves the problem again.

BTW, there is another issue unsolved, as XWLAN does not remove all 
entries of the route table (display with "netstat -r") that belong the 
the just deleted interface. As far as I see it here, this is no problem 
with that - once the ARP table is flushed, the old routes are not any 
longer used. Until XWLAN flushes these route entries, you may want to 
cleanup at least the host routes of a deleted interface by executing a 
"route -fh" on both connect and disconnect events. As the old routes 
currently do no lead to an error, XWLAN currently doesn't do that at 
all, as this clears all host routes, and not only the one of the desired 
interface. If a route table cleanup is implemented one day, it will 
cleanup the entries for the deleted interface only.

Finally, I do not understand why your access point would have two IP 
addresses, and even in the same IP subnet, isn't that an error ? 
Interesting, IMHO it should have ony one IP address...

thanx, Christian

-------------------------------------------------

Christian Langanke
COS2E & CWSE
Team OS/2 Ruhr e.V.
cla@clanganke.de

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