why cant i associate with 2 SSIDs from the same WLAN card

[fatso485]

Posted May 06, 2007 08:54 If the Access point can broadcast more than one SSID on the same channel using only one radio. how come my PC can only associate with only one SSID

i need to be connected to two different wirless networks that are broadcast from the same AP. can this be done?? if so, how?

 

[jlazzaro]

you're gonna need 2 wireless cards to connect to 2 differenet networks. if their both on the same AP, why?

if you're trying to double your wireless speed, this is not the way.

 

[fatso485]

i am not trying to double the speed. i want to have the ability to connect on two different subnets

i just want to understand why its not technically feasable to get one wlan card to connect to two diffent ssids while its very easy for an AP to broarcast more than 1 ssid even though it has one radio

 

[spidey07]

Because of the way the protocol (802.11 g/a) operates it is impossible.

The association between client and AP occurs at layer2, this binds the client to the access point. The SSID is just a human friendly means of defining a layer2 network.

It's the same as you can't connect to two networks at layer2 with any other technology.

 

[fatso485]

still a little unclear spidey

why cant they design the driver to have the ability to talk to two or more layer 2 sessions. arnt they already doing something similar on the AP to give it the ability to broadcast more one SSID onn the same channel

also if you are running a virtual machine can you set the wlan card to assosiate with one ssid on the emulated machine and assosite with another on the host machine all at the same time

 

[spidey07]

Look up the association process and 802.11 g management frames to get a deeper look.

The multiple SSIDs can be broadcast because it is the AP that is providing the service set. The clients then choose which one they want to associate with and from then on you are bound by the capabilites of the 802.11 g protocol.

 

[ScottMac]

You have to think of the SSID as a virtual wire/cable. You cannot plug the same (cabled) NIC into two different switches at the same time, you cannot connect two SSIDs from the same NIC for basically the same reason.

Good Luck

Scott

 

[aknightsa]

Originally posted by: ScottMac
You have to think of the SSID as a virtual wire/cable. You cannot plug the same (cabled) NIC into two different switches at the same time, you cannot connect two SSIDs from the same NIC for basically the same reason.

the channel is considered to be the physical media (as your example the cable)...

with Ethernet you can connect to two networks using one NIC card.. and as same thing now.. i have been able to get two IP addresses using one WLAN card but not able to connect to two SSID's from one as well... the question here is where does this limitation come from.. is it from the AP? from the WLAN card? or from the OS???

 

[nweaver]

Originally posted by: aknightsa

Originally posted by: ScottMac
You have to think of the SSID as a virtual wire/cable. You cannot plug the same (cabled) NIC into two different switches at the same time, you cannot connect two SSIDs from the same NIC for basically the same reason.

the channel is considered to be the physical media (as your example the cable)...

with Ethernet you can connect to two networks using one NIC card.. and as same thing now.. i have been able to get two IP addresses using one WLAN card but not able to connect to two SSID's from one as well... the question here is where does this limitation come from.. is it from the AP? from the WLAN card? or from the OS???

NO...the channel is NOT the "media"...the SSID is. If you can plug your NIC into one port and be on 2 different VLANS (not subnets, but VLAN, different Layer 2 network) then you have to ru n an additional protocol, like dot1q trunking.

neither dot1q nor ISL trunking protocols are supported over 802.11. It's a limitation from the standard, not the card, not the AP, not the OS.

 

[kevnich2]

I think at this point it's safe to say that this guy isn't going to get why he can't do this. Point blank, what your wanting cannot be done. If you want to connect to two WLAN's on the same machine, you'll need two WLAN cards to do it. Connecting to two networks may cause it's own problems unless you know what your doing and have a very good reason to do it. A single computer cannot operate with two gateway addresses on it.

 

[aknightsa]

what nweaver said is logical... the drawback is from the protocol itself...

but for the issue of only being able to have one IP on a NIC at a time.. i say go and experiment with Windows or linux!

you can have more than one gateway on a computer at a time.. when doing so, you just need to play with the routing tables... very easy..