where does IP address come from in Ad-hoc mode when using WiFi adaper?

  • Thread starter Thread starter Eric
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E

Eric

hello guys,

In my pocket pc, I found when I the machine has an IP address in ad-hoc
mode, although I let "the server assign the IP address". My understanding is
there are no DHCP servers over there, so where does the IP address come
from?

BTW, the IP address is always the same every time I tried to connect.

THanks,

Eric
 
Is it 169.x.x.x ?

If so, this is an autoconfigured address and means it can't find a DHCP
server.
 
Could be coming from a BOOTP device or that it tries to connect to a DHCP
server, cannot find one then assigns itself an existing address

Maybe?
 
The IP address is always 169.254.219.xx. Mask 255.255.0.0.

Paul what did you refer to when you say "an existing address"? It seems not
correct. I tried following test:
1. use static IP and assign it a new IP address;
2. restart, I find that new IP address is used. That is quite normal;
3. change it to "Server-assigned IP address". restart;
4. I found the old IP address appear again.

I am also sure within step 3 and 4, the machine did not connect to any AP.
So it did not receive any IP from DHCP.

Seems like the IP is a ghost IP...maybe PPC use some algorithm to obtain it,
say, calculate from adapter's MAC address?
 
Eric said:
The IP address is always 169.254.219.xx. Mask 255.255.0.0.

Paul what did you refer to when you say "an existing address"? It
seems not correct. I tried following test:
1. use static IP and assign it a new IP address;
2. restart, I find that new IP address is used. That is quite normal;
Click to expand...

Do you have connectivity then? Can you ping your router/anything on the
Internet/your network?
3. change it to "Server-assigned IP address". restart;
4. I found the old IP address appear again.
Click to expand...

Sounds consistent.
I am also sure within step 3 and 4, the machine did not connect to
any AP. So it did not receive any IP from DHCP.

Seems like the IP is a ghost IP...maybe PPC use some algorithm to
obtain it, say, calculate from adapter's MAC address?
Click to expand...

It's not a ghost - it's an autoconfigured address, as I said in my reply.
See http://www.webopedia.com/TERM/A/APIPA.html for more info.

This means your computer can't find a DHCP server - can indicate that a)
there isn't one on your network or b) you have a problem with your NIC or
connection.....since you're on wireless, are you using WEP? Got the WEP key
entered properly?
 
Eric said:
The IP address is always 169.254.219.xx. Mask 255.255.0.0.

Paul what did you refer to when you say "an existing address"? It seems not
correct. I tried following test:
1. use static IP and assign it a new IP address;
2. restart, I find that new IP address is used. That is quite normal;
3. change it to "Server-assigned IP address". restart;
4. I found the old IP address appear again.

I am also sure within step 3 and 4, the machine did not connect to any AP.
So it did not receive any IP from DHCP.

Seems like the IP is a ghost IP...maybe PPC use some algorithm to obtain it,
say, calculate from adapter's MAC address?
Click to expand...

An IP address of 169.254.xxx.xxx indicates you can't see a DHCP server.
PPC (or at least my model) has an AutoDHCP feature where it tries to
get a DHCP IP address at a timed interval in certain states. It uses
169.254.xxx.xxx (private IP address) as a local IP address until it can
get a "real" IP address from DHCP. Oh yeah, make sure you disconnect
ActiveSync before you try to connect too ;)
 
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