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#296082 - 30/03/2007 18:56 Sharing an IP address between two interfaces
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
This is in reference to Windows, but I'd be interested in other OSes, too.

Is there any way that I can get Windows to assign the same IP address to a wired and a wireless network interface so that transitioning between the two is more seamless?

One of my newest favorite Windows irritations is when Windows decides that it needs to cycle my wireless connection for no apparent reason and it decides that the IP address associated with it needs to go away. This is equivalent to unplugging a network cable and having it decide to remove your IP address instead of it being a temporary network outage.
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Bitt Faulk

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#296083 - 30/03/2007 19:16 Re: Sharing an IP address between two interfaces [Re: wfaulk]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14491
Loc: Canada
Quote:
This is in reference to Windows, but I'd be interested in other OSes, too.

Is there any way that I can get Windows to assign the same IP address to a wired and a wireless network interface so that transitioning between the two is more seamless?

One of my newest favorite Windows irritations is when Windows decides that it needs to cycle my wireless connection for no apparent reason and it decides that the IP address associated with it needs to go away. This is equivalent to unplugging a network cable and having it decide to remove your IP address instead of it being a temporary network outage.

Do what I do: configure the DHCP server to assign the same IP address for both MACs.

Cheers

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#296084 - 30/03/2007 19:17 Re: Sharing an IP address between two interfaces [Re: mlord]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
There's a variety of reasons that's a pain in the ass in my situation, but I don't even know if it will work under Windows.
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Bitt Faulk

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#296085 - 30/03/2007 19:18 Re: Sharing an IP address between two interfaces [Re: mlord]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14491
Loc: Canada
Quote:

Do what I do: configure the DHCP server to assign the same IP address for both MACs.


Mmm.. I wonder if your OS might allow something similar client-side: assign exactly the same MAC address to both interfaces ?

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#296086 - 30/03/2007 19:22 Re: Sharing an IP address between two interfaces [Re: wfaulk]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
I'm able to do this with assigning fixed IP addresses on the client. Windows gripes at me each time I go into the network properties box (hey, you've got an IP address on another interface that's the same! Are you sure you really meant to do it that way?) but it works.
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Tony Fabris

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#296087 - 30/03/2007 19:27 Re: Sharing an IP address between two interfaces [Re: mlord]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Under Windows, MAC address reassignments are handled by the driver, some of which provide the facility, others of which don't. Besides, having the same MAC address on a network is bad, even if it's going to the same computer.
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Bitt Faulk

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#296088 - 30/03/2007 19:28 Re: Sharing an IP address between two interfaces [Re: tfabris]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Yeah, I just tried that and, for some reason, it prevents the wireless authentication from working.
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Bitt Faulk

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#296089 - 30/03/2007 19:44 Re: Sharing an IP address between two interfaces [Re: wfaulk]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
Quote:
Yeah, I just tried that and, for some reason, it prevents the wireless authentication from working.

The only reason I could see that happening is if the LAN cable was plugged in at the same time you were trying to authenticate wirelessly. This little stunt only works when you use one connection or the other. You can't do both simultaneously.

Either that or the authentication was trying to go by MAC address, too, and you didn't tell the authentication server to take both the wired and the wireless mac addresses.
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Tony Fabris

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#296090 - 30/03/2007 21:15 Re: Sharing an IP address between two interfaces [Re: wfaulk]
gbeer
carpal tunnel

Registered: 17/12/2000
Posts: 2665
Loc: Manteca, California
Quote:
This is in reference to Windows, but I'd be interested in other OSes, too.

Is there any way that I can get Windows to assign the same IP address to a wired and a wireless network interface so that transitioning between the two is more seamless?

One of my newest favorite Windows irritations is when Windows decides that it needs to cycle my wireless connection for no apparent reason and it decides that the IP address associated with it needs to go away. This is equivalent to unplugging a network cable and having it decide to remove your IP address instead of it being a temporary network outage.


If you make sure not to enable both interfaces at the same time, you should be able to assign the same IP to each.
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Glenn

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#296091 - 30/03/2007 21:16 Re: Sharing an IP address between two interfaces [Re: gbeer]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Yeah, I want them both up at the same time. What I want is seamless movement from wired to wireless. If there's some other way to do that, that'd be great, too.
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Bitt Faulk

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#296092 - 30/03/2007 21:36 Re: Sharing an IP address between two interfaces [Re: wfaulk]
gbeer
carpal tunnel

Registered: 17/12/2000
Posts: 2665
Loc: Manteca, California
i've never seen that before. At a guess it would take a virtual interface that dynamically enables whichever bit of hardware is to be favored. e.g. Use the wired if connected, otherwise use the wireless.

As I said, never seen that before.

Edit: After some googeling the term wanted is "Ethernet Failover".


Edited by gbeer (30/03/2007 22:00)
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Glenn

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#296093 - 30/03/2007 21:43 Re: Sharing an IP address between two interfaces [Re: gbeer]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Okay, I was hashing this out and having both interfaces up at the same time doesn't make any sense.

Basically, all I want is something that will allow you to say that two interfaces are on the same logical network and have it use the same IP on the "best" interface, based on, first, link status, and then anything else -- speed, whatever. And it has to be application transparent.

What I mean by that is, if I lose link on my wireless connection with Windows, every long-term connection immediately bombs out, rather than waiting to see if it will regain link two seconds later. I want to be able to be using my wired interface, then unplug to walk across the room and not have any sort of hiccup.
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Bitt Faulk

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#296094 - 30/03/2007 22:18 Re: Sharing an IP address between two interfaces [Re: wfaulk]
gbeer
carpal tunnel

Registered: 17/12/2000
Posts: 2665
Loc: Manteca, California
Yep the term is failover, though none of the googel results were related to doing this on a single machine. All the results seemed to be related to the operation of servers.
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Glenn

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#296095 - 30/03/2007 22:32 Re: Sharing an IP address between two interfaces [Re: wfaulk]
drakino
carpal tunnel

Registered: 08/06/1999
Posts: 7868
Short answer, no.

Not even in Vista with the new network stack.

It might be possible if you had some sort of network teaming setup and bound the two interfaces into only one that Windows sees, but I haven't dug enough to find software that will do this in a generic setup. Plenty of server NIC drivers do this though.

And having this setup on my Mac laptop for years now, I can understand why you want it. It's so nice to be able to start a file copy while on wireless, realize it's dirt slow, and go and find an ethernet cable to plug in without interrupting the transfer.

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#296096 - 30/03/2007 23:45 Re: Sharing an IP address between two interfaces [Re: drakino]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
How do you set it up on the Mac?
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Bitt Faulk

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#296097 - 30/03/2007 23:58 Re: Sharing an IP address between two interfaces [Re: gbeer]
wfaulk
carpal tunnel

Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
Oh yeah. I guess it is just HA, just looked at from a different viewpoint. So, for Windows, that's going to be a commercial product. At least until MS incorporates a lousy version of it into the OS.
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Bitt Faulk

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#296098 - 31/03/2007 00:02 Re: Sharing an IP address between two interfaces [Re: wfaulk]
drakino
carpal tunnel

Registered: 08/06/1999
Posts: 7868
Just as Mark described, my server assigns the same IP to both my wireless and wired MAC addresses.

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#296099 - 31/03/2007 01:40 Re: Sharing an IP address between two interfaces [Re: wfaulk]
Attack
addict

Registered: 01/03/2002
Posts: 599
Loc: Florida
I use IBM's Access Connections program to auto switch to a from Wired / Wireless. It can even detect the SSID and auto switch to diffenent network profiles. I'm sure someone else makes something like it, try searching shellcity.net.
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Chad

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#296100 - 31/03/2007 02:16 Re: Sharing an IP address between two interfaces [Re: gbeer]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14491
Loc: Canada
Quote:
i've never seen that before. At a guess it would take a virtual interface that dynamically enables whichever bit of hardware is to be favored. e.g. Use the wired if connected, otherwise use the wireless.

As I said, never seen that before.


It's called a "bridge device" under Linux.

Basically, configure the wireless i/f and the wired i/f as members of a bridge, and assign a single IP address to the bridge itself, rather than to the member interfaces.

I'm sure that MS must have heard of this kind of thing already, right?
Linux has had it for (many) years already.

-ml


Edited by mlord (31/03/2007 02:19)

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#296101 - 31/03/2007 03:42 Re: Sharing an IP address between two interfaces [Re: mlord]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
There is a bridge feature under windows, you just select two interfaces under network properties and rightclick and select bridge networks. Dunno if it's the same thing, I always thought it was the new way to do internet connection sharing, which is a different thing.
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Tony Fabris

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#296102 - 31/03/2007 03:44 Re: Sharing an IP address between two interfaces [Re: tfabris]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
Ah, I see, it's a genuine network bridge.
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Tony Fabris

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#296103 - 31/03/2007 19:46 Re: Sharing an IP address between two interfaces [Re: wfaulk]
adavidw
addict

Registered: 10/11/2000
Posts: 497
Loc: Utah, USA
I dunno. It just always works for me, no setup required. One of those things the Mac just does right, I guess.
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-Aaron

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