Superhub SH to modem mode - keeping the same IP

George_w · 29-09-2011, 21:22

Hi all,

I need to keep my IP address that's currently assigned to my SH, but when I place the SH is modem only mode, the IP address is different. I understand this is because of the mac address which is being "learned" from what ever is connected to port one.

My MAC address of the SH ends in :cc and when viewing the source on the status, the device mac (HTML commented) ends in :cd. While in SH mode, running the command arp -a shows that's 192.168.0.1 ends in :cf

The starting MAC address is the same for all of the above with just the last 2 changing.

I have set my NiC to each one of these addresses, each time restarting the modem but always returning a private ip address. I have given each restart at least 2 minutes just incase.

I'm not sure what to do next. Am I using the wrong MAC address? Or is it just not Possible at all? It's very important for me to keep the same IP address due to work reasons, and would take too long to get everything changed as I've just gone through this process the other week due to being upgraded to the SH

I hope someone can shed some light on this.

P.s the ip address I have posted from is from another connection due to not being at home.

General Maximus · 30-09-2011, 07:52

You have got yourself in a right pickle dude.
mac addresses should be globally unique so you trying to change the address on your laptop/pc to that of one of the ports on the hub screws things up big time because it is basically seeing two of the same and nothing will work, which is why windows is using apipa.

The global ip address assigned to you is done by the cmts (Virgin). I don't know if it would change depending whether you are in modem mode or router mode but normally even when your dhcp lease expires and you renew it, you always pretty much end up with the same ip address again. The ip address of your laptop/pc will be different this time because in router mode, the hub will have the global ip address and assign local 192.168...... addresses to devices on the lan whereas in modem mode, unless you are using another router, your machine will have the global address.

If virgin gives you different ip addresses depending what modem mode you are in, there is no way around it other than using dns instead of letting everyone know what your ip add is.

Graham M · 30-09-2011, 08:34

Are you connecting the PC directly to the SH in Modem mode?

George_w · 30-09-2011, 09:24

I was setting the MAC addr on my actual laptop, and connecting the SH directly to the laptop. (It was just easier than using the router administration page to keep changing the MAC etc)

I never had this problem when I originally had my old modem and swapped routers for a new one (I just copied the WAN MAC from the old router, and updated my current router with that MAC address) and it worked perfectly well (that would be because the old modem I had was based on a "learned mode?")

Now I was assuming that the SH is doing the same thing (when in modem mode), as when you use a different NIC with a different MAC and reboot the SH, you get a different IP address, but if you swap them back around, you get the same IP address previous to what you had before - IE. :00 could of been *.*.*.88 and :01 could of been *.*.*.100 - hope I haven't made that too complicated.

I have also seen a couple of posts saying that normally, the MAC address to set would be one hex higher than that on the side of the SH, but like I said previously this isn't working.

Kymmy · 30-09-2011, 09:34

It's purely dependant on if the router MAC on the SH is a unique address or if it duplicates the first attached device.. I'm likely to think that it's unique but others would know better.

George_w · 30-09-2011, 15:51

So there really is no possible way to find it out?

Chrysalis · 02-10-2011, 13:05

yep you would also need to change the MAC of the superhub to remove the conflict, since you cant you stuck.

George_w · 02-10-2011, 14:07

I'll just have to bite the bullet and just get a new IP and a busy day updating IP's again

The only problem I have with the SH is once you walk out the room, the wifi signal is poor or not even available (thats on 2.4ghz)