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[majnu]

[Moderator note: This topic has been created by splitting off the following posts from the "Zyxel VMG8924 as modem - DHCP?" thread.]

Hi
Using the search feature I "think" I have the same issue as the OP. I consider myself a novice so please bear with me.

My VMG8924 is setup as modem into my Asus AC87U. Since I wanted to install Merlin AdGuard I ran into the issue of what the members of Smallnetbuilder described as double NAT. I'm struggling to understand the terms but from what I understand there is an IP conflict somewhere, which when I reboot the modem it is stated on my routers homepage which only goes away when I reboot so I can access the internet.



What IP values do I need to enter on the modem and router to resolve this please as I'm at my wits end 

Screenshots for router

https://imgur.com/63FOsKS

https://imgur.com/yC3iNQR

https://imgur.com/fPZuEsu

[majnu]

I've been given some advise to try out. On the connection status page I can only see my PC and no other connections so how do I go about finding my IP address of my router provided by the modem?

On Wan Connection page of the RT-AC87U

set connection to static.

then where the WAN IP settings are (on the same page)

set the WAN IP address to the IP address of provided by the Zyxel to the -RT-AC87U

subnet 255.255.255.0

default gateway, The IP address of Zyxel.

You can set DNS settings to whatever you like on this page 1.1.1.1 1.0.0.1


On the DHCP page of RT-AC87U

Set the routers IP to 192.168.2.1

This will change the IP range given to clients to 192.168.2.1

[Uwain]

I'm a total noob, so I may have some terminology mixed up and completely wrong ideas - but I'm trying!!

Double NAT is where you have 2 routers performing NAT... if you have 1 router behind a modem (or router in Modem only/bridged mode) there should not be any NATing on the modem.
You should be able to find any IP addresses assigned by DHCP on your Zyxel by plugging a computer into another LAN port on the Zyxel and accessing the GUI (ie type in the modem IP address in a browser).  If your Zyxel is connected to your router via your routers WAN port (like it should be for PPPoE) I dont think it will be assigned an IP address by your Zyxel (it will be assigned by your ISP).
On the status page just click your router and click info.


On OpenWRT router I created an interface called MODEM with an IP address in the same subnet as the modem. The modem is in a different subnet to the router.
When I first set up the MODEM interface I set the gateway to the IP address of the modem - this fails, and is not the way to do it! When I subsequently leave the gateway blank the internet works fine and I can access the modem from my LAN.

In my setup the WAN port on my router has a VLAN tag (eth0.2) - but I believe you can achieve something very similar with virtual interfaces (ie eth0:2) which you should be able to setup on your Asus from the CLI (I did this before I got the OpenWRT router on a RT-AC52U - but I no longer have that config).

So, the router has an interface and IP address on both subnets and an interface and IP address on the Internet (PPPoE).

Modem IP: 192.168.1.1
Router IP: 192.168.0.1
Router MODEM interface static IP on eth0.2: 192.168.1.2
Router PPPoE interface on eth0.2

Interfaces PPPoE and MODEM are, of course, in my WAN firewall zone.

I can't find my original instructions for my Asus... but from https://forum.kitz.co.uk/index.php/topic,14621.0.html

Code: [Select]

# Create virtual interface on router assuming modem is on 192.168.1.1
ifconfig eth0:1 192.168.1.2 netmask 255.255.255.0
#IP Tables v1.3
iptables -t nat -I POSTROUTING -s ! $(nvram get lan_ipaddr) -d 192.168.1.0/24 -j SNAT --to 192.168.1.2
#or IP Tables v1.4
iptables -t nat -I POSTROUTING ! -s $(nvram get lan_ipaddr) -d 192.168.1.0/24 -j SNAT --to 192.168.1.2

There appears to be an alternative where you can do the VLAN tagging on the modem, but I have always done it on the router...
 
VMG3925-B10B getting stats over WAN cable.

There are loads of alternatives available if you are not comfortable with any of the above...

Result of a Google search

[Moderator edited to simplify the above two links.]

[Uwain]

I think I originally got my ideas from https://wiki.dd-wrt.com/wiki/index.php/Access_To_Modem_Configuration

and my notes just say

Code: [Select]

#ddwrt show interface ==> # `nvram get wan_ifname`

#bridging to modem (192.168.1.1) on wan interface (vlan2)
ifconfig vlan2:0 192.168.1.2 netmask 255.255.255.0

#routing to the new interface
iptables -t nat -I POSTROUTING -o vlan2 -j MASQUERADE

simples!!!!!
I have no idea what MASQUERADE is... but pretty sure this worked on my Asus router.

PS My Asus was old and cheap, and its NVRAM was always full which I'm certain led to problems... so I also used this command...

Code: [Select]

#clear empty nvram variables
for line in `nvram show | grep ^[^=]*=$ `; do var=${line%*=}; nvram unset $var; done; nvram commitit seemed to help and certainly freed up some memory.

[jaydub]

Is there any reason you want the modem and router on separate networks.

I have my modem (in my case a Draytek Vigor 2762 in bridge mode) configured as 192.168.1.1 and My router (a Netgear Orbi) configured as 192.168.1.2 with DHCP on the Orbi handing out addresses from 192.168.1.3 upwards.

(A word of advice: you might get more response if you had started a new thread to ask your questions)

[Moderator edited to change 192.168.11 to 192.168.1.1]

[Uwain]

Is there any reason you want the modem and router on separate networks.

I have my modem (in my case a Draytek Vigor 2762 in bridge mode) configured as 192.168.1.1 and My router (a Netgear Orbi) configured as 192.168.1.2 with DHCP on the Orbi handing out addresses from 192.168.1.3 upwards.

(A word of advice: you might get more response if you had started a new thread to ask your questions)

[Moderator edited to change 192.168.11 to 192.168.1.1]

Me?
I'm not sure... I thought I had tried everything on one subnet originally years ago (Netgear in modem mode with the Asus Router) as it seemed to be the logical solution... but it didn't work. I must have done something else wrong at the time... I can't remember.
The solution I found split the networks... so thats what I did and have always done since!! Thats what happens when you dont really know what you're doing.

I wasn't actually looking for help in this thread - I was trying to help @majnu... apologies if that wasn't clear!! lol

But now you have me thinking... is there any advantage in reconfiguring to have everything in one subnet?

[majnu]

I'm a total noob, so I may have some terminology mixed up and completely wrong ideas - but I'm trying!!

Double NAT is where you have 2 routers performing NAT... if you have 1 router behind a modem (or router in Modem only/bridged mode) there should not be any NATing on the modem.
You should be able to find any IP addresses assigned by DHCP on your Zyxel by plugging a computer into another LAN port on the Zyxel and accessing the GUI (ie type in the modem IP address in a browser).  If your Zyxel is connected to your router via your routers WAN port (like it should be for PPPoE) I dont think it will be assigned an IP address by your Zyxel (it will be assigned by your ISP).
On the status page just click your router and click info.


On OpenWRT router I created an interface called MODEM with an IP address in the same subnet as the modem. The modem is in a different subnet to the router.
When I first set up the MODEM interface I set the gateway to the IP address of the modem - this fails, and is not the way to do it! When I subsequently leave the gateway blank the internet works fine and I can access the modem from my LAN.

In my setup the WAN port on my router has a VLAN tag (eth0.2) - but I believe you can achieve something very similar with virtual interfaces (ie eth0:2) which you should be able to setup on your Asus from the CLI (I did this before I got the OpenWRT router on a RT-AC52U - but I no longer have that config).

So, the router has an interface and IP address on both subnets and an interface and IP address on the Internet (PPPoE).

Modem IP: 192.168.1.1
Router IP: 192.168.0.1
Router MODEM interface static IP on eth0.2: 192.168.1.2
Router PPPoE interface on eth0.2

Interfaces PPPoE and MODEM are, of course, in my WAN firewall zone.

I can't find my original instructions for my Asus... but from https://forum.kitz.co.uk/index.php/topic,14621.0.html

Code: [Select]

# Create virtual interface on router assuming modem is on 192.168.1.1
ifconfig eth0:1 192.168.1.2 netmask 255.255.255.0
#IP Tables v1.3
iptables -t nat -I POSTROUTING -s ! $(nvram get lan_ipaddr) -d 192.168.1.0/24 -j SNAT --to 192.168.1.2
#or IP Tables v1.4
iptables -t nat -I POSTROUTING ! -s $(nvram get lan_ipaddr) -d 192.168.1.0/24 -j SNAT --to 192.168.1.2

There appears to be an alternative where you can do the VLAN tagging on the modem, but I have always done it on the router...
 
VMG3925-B10B getting stats over WAN cable.

There are loads of alternatives available if you are not comfortable with any of the above...

Result of a Google search

[Moderator edited to simplify the above two links.]

So I am trying to setup my router with a static IP using the below table I made for reference with the hope this solves the double NAT problem:



However when I set a static IP I l cannot connect to the internet and on my router I do not see my public IP.

Now I don't know if this is because I am conflicting with Bridge Interface group IP and whether I thus need to change my LAN IP to not be the same.



In Static DHCP on the modem it points to my routers MAC address



When I leave it as Automatic IP in routers setup page using the settings in the first image I can connect to the internet but then cannot access the Zyxel especially after following this: https://kitz.co.uk/routers/zyxel_VMG8324-B10A_bridge.htm

Plugged LAN into port 4 and configured an interface group as shown in the bottom of the link. I even plugged a laptop directly into the modem with 192.168.1.1 and it wouldn't allow me access it's interface page, so I'm truly at a loss

[meritez]

So I'm looking at your attachments and I'm looking at https://kitz.co.uk/routers/zyxel_VMG8324-B10A_bridge.htm

I really don't know where you're going wrong, but the article linked hasn't got any of the screenshots you're providing...

[majnu]

So I'm looking at your attachments and I'm looking at https://kitz.co.uk/routers/zyxel_VMG8324-B10A_bridge.htm

I really don't know where you're going wrong, but the article linked hasn't got any of the screenshots you're providing...

I don't know what to do know either.
Do I set all the Gateways to 192.168.1.1 or leave it as 192.168.2.1 on the router.

[meritez]

I don't know what to do know either.
Do I set all the Gateways to 192.168.1.1 or leave it as 192.168.2.1 on the router.

I would reset the zyxel and follow the article.

[majnu]

I would reset the zyxel and follow the article.

Is it because my router IP is not in the same subset?



Modem is 192.168.1.1
Router is 192.168.2.1

[meritez]

Is it because my router IP is not in the same subset?



Modem is 192.168.1.1
Router is 192.168.2.1

Possibly.

Let's try a working configuration first and then work towards what you are trying to achieve.

[jaydub]

Just set your 8924 to have a LAN IP address to 192.16.8.1.1

Your ASUS is set to 192.168.1.2 and its DHCP is serving IP addresses from 192.168.1.4 to 192.168.1.254

With the subnet mask you have set of 255.255.255.0 everything should work.

If you really want everything to work with your LAN IP address on 192.168.2.1 I think (and I do stand to be corrected) that you would need a subnet mask of 255.255.253.0

[majnu]

Just set your 8924 to have a LAN IP address to 192.16.8.1.1

Your ASUS is set to 192.168.1.2 and its DHCP is serving IP addresses from 192.168.1.4 to 192.168.1.254

With the subnet mask you have set of 255.255.255.0 everything should work.

If you really want everything to work with your LAN IP address on 192.168.2.1 I think (and I do stand to be corrected) that you would need a subnet mask of 255.255.253.0

When I add an interface group to LAN1 with ptm0.1 isn't that then sending internet to the WAN port of the router? That has an IP address of 192.168.2.1?

The bridging group has to be the new (not default) group because only the default group has access to the gui/telnet which we need to access stats from the LAN.

Isn't the 192.168.2.1 now my default gateway? That is why I have been trying to setup my DHCP around it.

Default Bridge 182.168.2.1


Default LAN 192.168.1.1


Thank you

[jaydub]

At the start of your thread, you have set up your DHCP settings on the Asus to be 192.168.1.4 to 192.168.1.254 and you have set your LAN IP address of the Zyxel to 192.168.1.2.

With a subnet mask of 255.255.255.0 the 192.168.2 subnet (which just has the 8924 on it) can't talk to devices on the 192.168.1 subnet.

So you have a few options:

• Leave everything as is but set the subnet mask to 255.255.253.0, so the two subnets can talk to each other
• Configure the ASUS to have a 192.168.2.2 IP address and the DHCP on the Asus to server out 192.168.2.4 to 192.168.1.254
• Set the LAN IP address of your router to be 192.168.1.2 which is in line with the Kitz link that Meritez provided earlier (other than a different allocation of IP address to the router)

I prefer keeping everything on the same subnet, as it makes it easier to get the stats off the Zyxels, but if you are not wanting to use DSLStats, there is no reason to go down this route.

I am currently using a Draytek Vigor in bridge mode rather than a Zyxel, but if you want some screen shots I can dig out a 1312 to give you some equivalent screen shots to your 8924 this evening.