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Airport Express and secondary DHCP allocations

MentalFabric

MentalFabric

macrumors 6502
Original poster
Mar 10, 2004
372
25
Hi all,

I've got airport express providing my wifi attached to a Thompson router - unfortunately the Thompson is fairly unreliable and needs to be restarted on a regular basis which takes down the whole network presumably as it provides the DHCP - this means airplay is interrupted when the router goes down.

So I'm wondering whether I can use the 'DHCP only' option on the AE in router mode to have it allocate IPs on either the same or a different range in order to keep at least the local network up when the router goes down. Does anyone know whether this would work or any other solution that would?
 
drsox

drsox

macrumors 68000
Apr 29, 2011
1,706
201
Xhystos
MentalFabric said:
Hi all,

I've got airport express providing my wifi attached to a Thompson router - unfortunately the Thompson is fairly unreliable and needs to be restarted on a regular basis which takes down the whole network presumably as it provides the DHCP - this means airplay is interrupted when the router goes down.

So I'm wondering whether I can use the 'DHCP only' option on the AE in router mode to have it allocate IPs on either the same or a different range in order to keep at least the local network up when the router goes down. Does anyone know whether this would work or any other solution that would?
Click to expand...

Can you turn off the local DHCP/NAT functions on the Thompson router (i.e. get it to act as only a modem) ? Then you can use the AE as the sole router with DHCP and NAT active, connecting to the Thompson as the modem.
 
Weaselboy

Weaselboy

Moderator
Staff member
Jan 23, 2005
34,132
15,595
California
MentalFabric said:
Hi all,

I've got airport express providing my wifi attached to a Thompson router - unfortunately the Thompson is fairly unreliable and needs to be restarted on a regular basis which takes down the whole network presumably as it provides the DHCP - this means airplay is interrupted when the router goes down.

So I'm wondering whether I can use the 'DHCP only' option on the AE in router mode to have it allocate IPs on either the same or a different range in order to keep at least the local network up when the router goes down. Does anyone know whether this would work or any other solution that would?
Click to expand...

You can setup the two devices on different subnets and that will allow you to leave DHCP on with both. So one would be on say 192.xxx.xxx.x and the other on 10.xxx.xxx.x.
 
MentalFabric

MentalFabric

macrumors 6502
Original poster
Mar 10, 2004
372
25
Thanks for the help guys, I can set up the router in bridged mode to use the AE for DHCP but I'm using a few ethernet ports on the router and I'd rather not have to find an ethernet switch to plug in to the AE so I think the preferred option would be to set up another subnet for the wifi on the AE - how would I go about that? When I try to switch to DHCP only mode it says I need to manually configure a WAN IP address...
 
Weaselboy

Weaselboy

Moderator
Staff member
Jan 23, 2005
34,132
15,595
California
MentalFabric said:
Thanks for the help guys, I can set up the router in bridged mode to use the AE for DHCP but I'm using a few ethernet ports on the router and I'd rather not have to find an ethernet switch to plug in to the AE so I think the preferred option would be to set up another subnet for the wifi on the AE - how would I go about that? When I try to switch to DHCP only mode it says I need to manually configure a WAN IP address...
Click to expand...

What you want is the Airport and Thompson on different ranges of addresses. Look at this screen in Airport Utility and you should see the AE is on the 10.xxx range. Check the Thompson to see what range it runs on. If it it already 192.xxx you are good to go. If the Thompson is 10.xxx, then change the AE to 192.xxx.

DdENV.png
 
drsox

drsox

macrumors 68000
Apr 29, 2011
1,706
201
Xhystos
Do you want the wired devices to see the wireless devices and vice versa ? If you do then IMO a switch is going to be necessary.
 
M

mic.o

macrumors newbie
Dec 12, 2011
2
0
Bridge Mode

Did you get this resolved?
Forgive me if this is already resolved, but I figured I'd share this in case you're still dealing with intermittent (or repetitive) network problems.

Your Thompson modem/router might be working fine. Sometimes, one of the problems when you have routers linked while on the same subnet is that you have the two sort of fighting to assign IP addresses. You get kicked off the network because you have too many chefs in the kitchen.

Here's what I do... but it's not the only option. However, it works great for having multiple routers on the same subnet and not have to switch networks to access different devices. I personally prefer this setup when I'm not using different subnets.

  1. Setup your Thompson Modem/Router same as normal as if you don't have another router.
  2. Set your Airport Extreme in Bridge Mode
    • Network Tab > Router Mode > Off (Bridge Mode)
    • Wireless Tab > Network Mode > Create Wireless Network (you fill in the rest of the info)
    • Internet Tab > Connect Using > DHCP
  3. Connect AE to Thompson Router with ethernet cable from LocalPort to LocalPort. DO NOT use "Internet Port" on AE. It won't hurt the devices, but it simply won't work because AE will be looking for different info.

With this setup, the Thompson router is the only one that assigns your IP addresses. The Airport Extreme functions simply as a Wi-fi, transmitting the IP addresses assigned by the Thompson router. Now, no matter which Wi-fi you use, you can access all your devices without switching networks – printers, Apple TV, Blu Ray device, AirPlay, etc.
 
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