Splitting DHCP from ADSL modem?

[Scuba_Steve]

Hopefully someone here will know the in's & out's to be able to offload the DHCP from the ADSL modem to a router?

What I have is an ADSL modem which I still want to do the PPPoA auth but I don't want it to distribute the ext IP to the many internal ones via DHCP I want that job to be passed onto the router attached to it.
The router only supports PPPoE auth so I can't pass that ability over & I'm trying to avoid double NATing if that is at all possible.

So how do I setup the ADSL modem to do the PPPoA authentication but for the router to issue the DHCP & effectively everything else?

[Big Dog]

Set a static on the modem and routers. Enable dhcp on the router. Job done.


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

Ps you'll. need to either reserve the 01 IP address in the dhcp for your modem or set your newly chosen static ip as your default gateway.


Stupid phone / Tapatalk, apologies in advance.

[Scuba_Steve]

So you're saying something like

ADSL=192.168.1.1; DHCP=Disabled
Router=192.168.1.2; Gateway=192.168.1.1; DHCP=192.168.1.5 - 192.168.1.254

[Big Dog]

I would also recommend setting an alternate up address on at least one PC. In case you ever lose dhcp off the router. Such as you need to swap it out with another router. Otherwise first hint you have an issue is none of your devices can connect once their registrations expire.


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

So you're saying something like

ADSL=192.168.1.1; DHCP=Disabled
Router=192.168.1.2; Gateway=192.168.1.1; DHCP=192.168.1.5 - 192.168.1.254

That was pretty much how mine was setup when I had a separate router for wireless.
I put registrations in for each network devices MAC address


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

Your ADSL will need two addresses.
One internal. 192.168.1.1 and one public ( you get this dynamically from ISP unless you are I a static ip)


Stupid phone / Tapatalk, apologies in advance.

[Gremlin]

Looks like you'll get it sorted.

You can only have one DHCP server within a network. Basically, turn off DHCP in modem, turn on in Router. Set appropriate range for DHCP (and make sure nothing has a static address inside the range).

[Big Dog]

Looks like you'll get it sorted.

You can only have one DHCP server within a network. Basically, turn off DHCP in modem, turn on in Router. Set appropriate range for DHCP (and make sure nothing has a static address inside the range).

If you desire a static IP within the range that is where reservations come in.
You can still apply the static IP but if not reserved that address may be handed out to another competing device.
If you use an IP high enough in the range so as to not ever be a cause of conflict (eg using .36 when you know there are only 25 devices) then you will be fine... but if you are going to have lots of static ip's (printers, NAS etc) better off having a separate range if your router does not support reservations.

[Scuba_Steve]

part the reason I wanna use the router rather than the modem is the router supports IP reservations & a guest network whereas the modem doesn't
I'm gonna give the setup ago tomorrow & hopefully it all runs smooth as the wife doesn't like to be disconnected from the interwebs for long too used to having it & I don't want the beatdown :baby:

[Gremlin]

If you use an IP high enough in the range so as to not ever be a cause of conflict (eg using .36 when you know there are only 25 devices) then you will be fine... but if you are going to have lots of static ip's (printers, NAS etc) better off having a separate range if your router does not support reservations.
Addresses aren't always handed out in order, can be random. RouterOS hands out top down more or less actually...

[Big Dog]

Addresses aren't always handed out in order, can be random. RouterOS hands out top down more or less actually...

All the domestic hardware I have used or set up for others starts at the bottom and scales up, releasing unused IPs after 14 days. The commercial gear I have used scales down, unless you set rules to the contrary.


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

Sure makes guessing the IPs of printers etc easier.

Fwiw printers are shocking on DHCP without reservations. They end up out of synch with clients without a print server. Even then some brands are useless at staying in synch.


Stupid phone / Tapatalk, apologies in advance.

[Gremlin]

Who puts a printer on DHCP (esp without reservation)?

One down on my list from some gormless tech that puts a static address on a device and the address is inside the DHCP range... Can take you months of random issues before you finally track down what's going on... (or you drill holes throughout your DHCP range)

[Big Dog]

Who puts a printer on DHCP (esp without reservation)?

One down on my list from some gormless tech that puts a static address on a device and the address is inside the DHCP range... Can take you months of random issues before you finally track down what's going on... (or you drill holes throughout your DHCP range)

There are times on a home network the simplest solution is the best solution.


Stupid phone / Tapatalk, apologies in advance.

[Scuba_Steve]

OK so here the next question, say I want to off load the NAT also to the router, can that be done while still having the modem do the PPPoA auth?
"My Bad" in advanced if it turns out to be a stupid question, probably had a bit too much to drink tonight & can't be arsed thinking for myself; Fucking round with technical things like networks is always better with booze... Well at-least more "fun" anyways

[Big Dog]

In theory. Although that wound involve turning off nat and opening same ports on modem. Then configuring nat on router. Not sure you would see any speed gain.


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

For that matter you could turn off the firewall altogether and offload that to the router also. Weather that would be smart or. Not would depend on the quality of your kit. Eg old one port modem and new multi port name brand router this would be a good idea. Other way round not so much.


Stupid phone / Tapatalk, apologies in advance.

[Gremlin]

Yeah, you can setup the modem to DMZ everything to the router (hell, if you want, some modems will support passthrough for the connection) but you'll need the services somewhere.

At this point, you should probably be mentioning the equipment used, in case anyone is familiar with it.

[Scuba_Steve]

The "Modem" is Allied Telesis AR256Ev3
The "Router" is Apple Airport Extreme Gen5

Oh & the firewall's always been off on the modem, cause... Meh, I live dangerous like that