Roaming on Linux across subnet- Help Needed

hi,
I have setup a 802.11b wireless network.I have got two access point
each on different subnet.They both have same SSID and encryption is
disable.I am trying roaming using a laptop with Linux Redhat 7.3 with
a linksys card(also tried this with DLink 650).Whenever I move my
laptop from the range of one access point to range of other AP, the IP
ADDRESS DOES NOT CHANGE!! Since the subnets are different, the network
connection will not work with same IP address.
The same configuration is working in Windows XP... as user moves from
one AP to another the IP address changes automatically... is there
something to be done in Linux that can make this work.??????

Any help will be highly appreciated...

Regards,
Kishore.

Since the AP's are on different subnets, you should probably give the AP's
different SSID's. The only way that the wireless network will know to DHCP
for a new IP is if it thinks its on a new wireless net. This is no
different than performing the same task with 10/100 ethernet. You unplug
from one andplug into another and get a new address. Most wireless clients
have the ability to search out multiple wireless nets automagically, but if
not, the client will have to change manually.

Gray

"kishore" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) m...
> hi,
> I have setup a 802.11b wireless network.I have got two access point
> each on different subnet.They both have same SSID and encryption is
> disable.I am trying roaming using a laptop with Linux Redhat 7.3 with
> a linksys card(also tried this with DLink 650).Whenever I move my
> laptop from the range of one access point to range of other AP, the IP
> ADDRESS DOES NOT CHANGE!! Since the subnets are different, the network
> connection will not work with same IP address.
> The same configuration is working in Windows XP... as user moves from
> one AP to another the IP address changes automatically... is there
> something to be done in Linux that can make this work.??????
>
> Any help will be highly appreciated...
>
> Regards,
> Kishore.

"Gray D. McCord" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Since the AP's are on different subnets, you should probably give the AP's
> different SSID's. The only way that the wireless network will know to
DHCP
> for a new IP is if it thinks its on a new wireless net. This is no
> different than performing the same task with 10/100 ethernet. You unplug
> from one andplug into another and get a new address. Most wireless
clients
> have the ability to search out multiple wireless nets automagically, but
if
> not, the client will have to change manually.

Maybe the fix is in the Q - why are the 2 APs in different subnets?

Roaming on APs implies that for seamless connectivity the end station doesnt
need to worry about which AP it is connected to - this also implies all the
APs and connected devices are in the same subnet.

If they must be in different subnets, then you need some sort of abstraction
between the physical IP address and the logical one used by your
applications - mobile IP is supposed to fix this kind of problem, but it
needs complex IP stack changes and router software. Or, see if you can find
some APs that understand VLANs (Cisco aironet 1200?).

Look on the Cisco web site for someone who claims to do this - personally i
look at this solution as a bigger set of problems than fixing the topology
so all APs are in the same subnet.....
>
> Gray
>
> "kishore" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) m...
> > hi,
> > I have setup a 802.11b wireless network.I have got two access point
> > each on different subnet.They both have same SSID and encryption is
> > disable.I am trying roaming using a laptop with Linux Redhat 7.3 with
> > a linksys card(also tried this with DLink 650).Whenever I move my
> > laptop from the range of one access point to range of other AP, the IP
> > ADDRESS DOES NOT CHANGE!! Since the subnets are different, the network
> > connection will not work with same IP address.
> > The same configuration is working in Windows XP... as user moves from
> > one AP to another the IP address changes automatically... is there
> > something to be done in Linux that can make this work.??????
> >
> > Any help will be highly appreciated...
> >
> > Regards,
> > Kishore.
--
Regards

Stephen Hope - remove xx from email to reply

Hi,
Well in your idea of having MobileIP Support, you believe that the
client has the same IP Address as the client moves across different
APs (whether in same subnet or not..).
What I am trying to implement is Mobility support using SIP(Session
Initiation Protocol), a protocol used for signalling of multimedia
sessions. With this, even if the IP Address changes the session would
continue seamlessly..(the user will not be aware of the changes ) ...
the basic idea of trying this is so that I can avoid the requirement
of MobileIP Support!!!! So I need to have two different APs on
different subnets..as my testbed.

Well in Wiindows I had no problem in the automatic change of IP
Address with change of AP.. I hope someone can help me for this on
linux.???

Thanx once again.
Kishore.



> Maybe the fix is in the Q - why are the 2 APs in different subnets?
>
> Roaming on APs implies that for seamless connectivity the end station doesnt
> need to worry about which AP it is connected to - this also implies all the
> APs and connected devices are in the same subnet.
>
> If they must be in different subnets, then you need some sort of abstraction
> between the physical IP address and the logical one used by your
> applications - mobile IP is supposed to fix this kind of problem, but it
> needs complex IP stack changes and router software. Or, see if you can find
> some APs that understand VLANs (Cisco aironet 1200?).
>
> Look on the Cisco web site for someone who claims to do this - personally i
> look at this solution as a bigger set of problems than fixing the topology
> so all APs are in the same subnet.....
> >
> > Gray
> >
> > "kishore" <(E-Mail Removed)> wrote in message
> > news:(E-Mail Removed) m...
> > > hi,
> > > I have setup a 802.11b wireless network.I have got two access point
> > > each on different subnet.They both have same SSID and encryption is
> > > disable.I am trying roaming using a laptop with Linux Redhat 7.3 with
> > > a linksys card(also tried this with DLink 650).Whenever I move my
> > > laptop from the range of one access point to range of other AP, the IP
> > > ADDRESS DOES NOT CHANGE!! Since the subnets are different, the network
> > > connection will not work with same IP address.
> > > The same configuration is working in Windows XP... as user moves from
> > > one AP to another the IP address changes automatically... is there
> > > something to be done in Linux that can make this work.??????
> > >
> > > Any help will be highly appreciated...
> > >
> > > Regards,
> > > Kishore.

kishore wrote on [10 Aug 2003 10:25:18 -0700]:
> Hi,
> Well in your idea of having MobileIP Support, you believe that the
> client has the same IP Address as the client moves across different
> APs (whether in same subnet or not..).
> What I am trying to implement is Mobility support using SIP(Session
> Initiation Protocol), a protocol used for signalling of multimedia
> sessions. With this, even if the IP Address changes the session would
> continue seamlessly..(the user will not be aware of the changes ) ...
> the basic idea of trying this is so that I can avoid the requirement
> of MobileIP Support!!!! So I need to have two different APs on
> different subnets..as my testbed.

So, your users don't keep persistant IP connection open? Like an ssh
session or the like?