DDWRT as Internet Gateway Only

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Rippey574
DD-WRT Novice


Joined: 10 Apr 2017
Posts: 11
Location: Elkhart, IN

PostPosted: Sun May 05, 2019 20:16    Post subject: DDWRT as Internet Gateway Only Reply with quote
I am having a hard time setting up a DDwrt router as a gateway to the internet only.

So I have Comcast business internet with multiple static ips. So I want this a the public interface. This will then go to a DD-WRT router.

The router needs to act as an internet gateway for the privet network to one of my static IPs. It can not be the DHCP or DNS. I would like to retain its SIP firewall.

The DD-WRT will then feed to the privet side switch, where other severs will provide the DHCP, DNS, Gateway IP.

I have the DNS all ready setup and DHCP and Gateway, that works well. But even after it assigns the computers there is no internet and and I can not ping the gateway ip. The local privet lan is accessible.

So I disabled the DHCP on the router, left it in gateway. The IP of the router is the default 192.168.1.1 I have even tried it as DHCP forwarder to the DHCP sever and still no internet access.

Attached is the vague network layout with just the privet and internet main part in it.

I am not sure what I am missing, any pointers or obvious mistakes? I can not use the built in DHCP and DNS and that is why I am going this route.

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eibgrad
DD-WRT Guru


Joined: 18 Sep 2010
Posts: 8034

PostPosted: Sun May 05, 2019 22:29    Post subject: Reply with quote
I'm not 100% sure I understand this configuration. You mentioned multiple static (presumably public) IPs from your ISP. But from the rest of the description that follows, I don't know if that is even relevant. So for the time being, I'm going to assume it isn't.

If you want something other than the dd-wrt router to provide DHCP and DNS services, that's not a problem. Just so long as the other DHCP server provides the correct gateway and DNS servers to those local clients. When using the DHCP server on the router, that's a non-issue. The router provides its own local IP to the DHCP clients as the gateway and DNS server.

The problem comes when the DHCP server is managed elsewhere. Now it's the responsibility of that DHCP server to make sure the returned default gateway and DNS server are correct for the local network the DHCP server is administering.

Is that the case?
Rippey574
DD-WRT Novice


Joined: 10 Apr 2017
Posts: 11
Location: Elkhart, IN

PostPosted: Sun May 05, 2019 22:37    Post subject: Reply with quote
Yes they are public ips.

I have the dhcp handing out the router address of 192.168.1.1 to its clients which is the same ip as the ddwrt router, but nothing will connect to the internet; it acts like the ddwrt router is not accepting the packets from the ips with the sever dns
eibgrad
DD-WRT Guru


Joined: 18 Sep 2010
Posts: 8034

PostPosted: Sun May 05, 2019 22:41    Post subject: Reply with quote
When one of those DHCP clients gets configured by the other DHCP server, does the client report the correct gateway and DNS server?

For example, if it's a Windows client, does issuing the ipconfig /all command from the command line show all the correct information?

P.S. And do NOT setup the dd-wrt router as a forwarder. Just disable the DHCP server entirely.
Rippey574
DD-WRT Novice


Joined: 10 Apr 2017
Posts: 11
Location: Elkhart, IN

PostPosted: Mon May 06, 2019 1:38    Post subject: Reply with quote
Thank you for your help, I got the if off forwarder now, but found my dns will not respond correctly on the local side now. So I will pluck through that issue and hopefully have an update later that says it all works fine.
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