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[RTouris]

Hi all, facing a somewhat trivial issue here with a new setup i try to migrate to in an existing FTTC implementation that I just can't get my head around. Every bit of help appreciated, especially from the network gurus here!

Kicking things off some non-essential recent history; A few years ago I followed the truly helpful guide found at https://kitz.co.uk/routers/zyxel_VMG8324-B10A_bridge.htm to setup a ZyXEL VMG8924 as a modem in bridge mode in front of an ISP's modem/router in order to be able to monitor my line's stats using the amazing DSLstats setup on a rPi4. Truth be told for some strange reason i didn't have to setup an interface group at the time since in some rather peculiar way I was able to access the WAN side of the ISP's modem without doing so. Skip a few years ahead which brings us to some power and interνet outages the connection was plagued with a few weeks back, so I decided to put the hardware to the test. In doing so I found out that the ISP's router was struggling somehow - freezing at times so instead of replacing it for a new one I went ahead and decided to replace it with an Edgerouter ER-X I had lying around in order to have more 'control' over the hardware on this particular site. To cut the story short the ER-X (expectedly) doesn't work out-of-the-box as the ISP's modem did in order to be able to access the WAN side of it, so I decided to go down the interface group trick in order to segregate the WAN traffic from the LAN traffic and use a second cable to poll the stats from the modem. However this also doesn't appear to work for me as in doing so for some other strange reason all traffic halts and it all goes pearshaped so to speak. I'm new to the ER-X stuff so I had it setup over the UI using the WAN+2LAN wizard, but in fiddling around with the settings and all I'm still unable to resolve this issue and get it back to working order which also includes accessing the Zyxel.

As things stand now I do have internet connectivity via a PPPoE call the ER-X makes to the ISP over the Zyxel and on the ER-X side of things still I have a DHCP server setup and running smoothly as well as some essential port forwards for VPN and other such rules and an SQM that all work fine. The one thing I can't be able to wrap my head around is accessing the ZyXEL in any way or form. Ping / ssh / tracerouting all fail miserably since without a second cable it obviously can't communicate with the LAN ports of the ZyXEL. In establishing a bridge interface group on the Zyxel according to the guide mentioned but **withough** having a cable connected nothing changes, still can't access the modem though. When connecting the cable, it all goes crumbling down.

Could someone point me to the right direction since I'm at a complete loss as to what I might be doing wrong. I'm sure this has to be some really stupid thing I'm doing wrong, yet I'm really stuck..

[Alex Atkin UK]

Firstly assuming you setup the Zyxel LAN side with a static IP address I'd try a PC directly connected to the LAN port also with a static IP address, just to confirm its actually working properly.

I can't think of any reason it shouldn't be working when hooked up directly to the LAN, although when I did it I had it hooked into a port on my pfSense box software bridging to the LAN in order to save a precious switch port for something more important.

[RTouris]

Thanks for the reply.

Yeap, the ZyXEL surely works as described when accessed through the LAN ports via a PC with a static IP in the same subnet. I just can't get the ER-X to connect to it via the interface group designated segregated LAN port to access the data behind it and connect to it as i did in the past. Given that the line still faces issues at times and the condition hasn't stabilized yet I'm afraid I'm unable to guide the technicians to find the root cause any longer..

[Alex Atkin UK]

Is this a separate LAN on the ER-X for this and if so is it a different subnet to the main LAN?

[RTouris]

Nope, same LAN, same subnet. For the sake of it i even tried hooking an additional router in between i.e. Zyxel (2.254) <-> ER-X (1.1) <-> 2nd router (2.1) with the additional cable running from LAN port of the Zyxel to any port on the 2nd router and still can't connect to it when accessing it from the ER-X. I CAN however access it when i connect the cable directly to the 2nd router, which makes no sense to me :/ Perhaps i need to set a static route of some sort on the ER-X in addition to the interface grouping on the Zyxel?!

[Alex Atkin UK]

You probably need to manually create a bridge for the LAN interfaces.

[meritez]

What's the subnet mask on the ER-X?

[RTouris]

That'd be 255.255.255.0. Having said that even if i set the ZyXEL in the ER-X's subnet i still can't access the ZyXEL behind the ER-X (since it's on the WAN side of the network). Granted there's the default firewall rules that might affect such traffic also, but at the end of the day the guide i refer to in the first post doesn't make any such mentions having set up the group interface to aleviate all of this fuss supposedly..

[vic0239]

For comparison, on my VMG1312-B10A I have just the default interface group with all WAN and Lan interfaces therein. For this interface group I have set the local IP address to 192.168.2.1 with the standard subnet mask of 255.255.255.0 on the Home Network tab. On my router running RouterOS I have added a new subnet (192.168.2.2/24) on the ethernet interface serving the WAN connection. RouterOS kindly added a dynamic static route for this subnet. This allows access to the Zyxel over the WAN connection at 192.168.2.1 in my configuration.

[RTouris]

For comparison, on my VMG1312-B10A I have just the default interface group with all WAN and Lan interfaces therein. For this interface group I have set the local IP address to 192.168.2.1 with the standard subnet mask of 255.255.255.0 on the Home Network tab. On my router running RouterOS I have added a new subnet (192.168.2.2/24) on the ethernet interface serving the WAN connection. RouterOS kindly added a dynamic static route for this subnet. This allows access to the Zyxel over the WAN connection at 192.168.2.1 in my configuration.

This is excellent info. So in other words you didn't follow the group interface per the guide quoted..Can i ask what the dynamic static route for this subnet appears under RouterOS? (i suppose this is mikrotik gear, im i right)?

[vic0239]

This is excellent info. So in other words you didn't follow the group interface per the guide quoted..

On this occasion no as I won't be using any of the LAN ports, however if you have a separate interface group for your WAN port just remember to select it from the drop down menu when defining the local IP address.

Can i ask what the dynamic static route for this subnet appears under RouterOS? (i suppose this is mikrotik gear, im i right)?

Yes MikroTik - quite a learning curve to get it to do what you need!  The static route is just the new subnet as the destination address and the name of the ethernet port as gateway (see attachment). These are also dynamic, hence the peculiar naming (I'm lazy).

[RTouris]

Great, i suppose there's enough info here to give my troubleshooting needs another go and will report back for future reference. Thanks all, any further help is always appreciated

[Alex Atkin UK]

On this occasion no as I won't be using any of the LAN ports

Then how are you connecting the router to the LAN?  One port for the uplink to the LAN, one port for the modems LAN side.

Even with WiFi, internally the WiFi is on a bridge and the LAN is also on that bridge (even if it doesn't have a physical ethernet port).  If the modem is on the same subnet, its LAN port too needs to be part of that bridge or you have two conflicting networks using the same subnet, or the modem port has no IP address assigned so naturally it wont work at all then.

This is likely why it worked connected to the second router.

[vic0239]

Then how are you connecting the router to the LAN?  One port for the uplink to the LAN, one port for the modems LAN side.

Same port for both. Local subnet on Zyxel is different to router and applied across all ports. Wan port on router has same subnet as the Zyxel with static route.

[Alex Atkin UK]

Right, my eyes got a bit crossed and read your comment as from the OP.

I never liked single cable solution without VLANs as I wonder what traffic might leak out onto the WAN network, even if it ultimately wont do anything.