DHCP pass-through behind PPPoE possible?

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi there@all,

i was wondering if a certain scenario is possible to solute with openwrt.

We have two business ISPs.
One is providing IPv4 directly via DHCP, plug and play. no hassle with that.
The other provides IPv4 via DHCP after PPPoE, encapsulated in VLAN.

We use enterprise hardware for firewall and routing purposes, many employees must configure it on a daily basis and luci is just not cutting it for them because we need different levels of user privileges when setting rules for network traffic. The embarassing point is, that this expensive hardware is not capable of connecting through PPPoE.

So my question is: Is it possible to use OpenWRT hardware to connect using PPPoE, but then passing all traffic through let another router behind do the NAT and DHCP?

Thanks for your replies

2

Yes.

This depends on exactly how you plan to do this. PPPoE assigns an IP address. So, you would have to create a LAN network for the downstream device to connect on its WAN, then it can do NAT and DHCP for the rest of the network users. "Pass-through" wouldn't be necessary.

I also assume you want to connect both ISPs, this is possible with mwan (Multiple WAN) scripts.

3

Thanks for the reply!

So, you would have to create a LAN network for the downstream device to connect on its WAN, then it can do NAT and DHCP for the rest of the network users. “Pass-through” wouldn’t be necessary.

Possibly i don't catch up on your point, but i understand that this is no different from a simple routing done by OpenWRT, in this case for a single device on the LAN side.

If i create a LAN on OpenWRT, i'd have to do some NAT for all devices connected to it for them to get a connection to the internet. That again would be NAT behind NAT, if a connected router use OpenWRT's LAN on it's WAN. Furthermore, WAN on the router would get an IP Adress within the local range of OpenWRT's LAN.

I might be asking the wrong question, but if PPPoE assigns an IP adress, is it possible to forward this certain IP address and unNATed traffic? The router/firewall behind is a single device asking on it's WAN for an IP Adress via DHCP connected to OpenWRT's LAN?

I also assume you want to connect both ISPs, this is possible with mwan (Multiple WAN) scripts.

Yes, but this issue is resolved otherwise and is not a problem.

Thanks for your patience with my question.

4

You don't have to NAT twice. Just turn off masquerade on the downstream router. Then it's a straight route.

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