2 Router Configuration, Computer Communication Issues between router

Here is the basic set-up:

Router #1: Connects to the Internet via the WAN port, DHCP is enabled. This is part of an established network that I can not change the settings on.

Router #2 (We are adding a new network): DD-WRT firmware, with the LAN and WLAN separated to isolate the WLAN to only communicate with the HOSTS on the LAN. DHCP is enabled for not the LAN and WLAN, which are different and bridged with router #2. The HOSTS on the LAN can communicate with the internet and can hit hosts on connected to router 1 via IP address, but not host names (not a big issue, think it is a DNS issue between router 1 and router 2. A local DNS server it setup on Router 2 to resolve HOST names within router 2. Router 2 is set to gateway, if changed to Router loose internet connectivity.

Problem: Any Host connected to router 1 cannot see any host connected to router 2. I can ping router #2 from a host on router 1. I know the easy fix it to establish a routing command from router 1, pointing to router 2 but I cannot change any setting within router 1.

For testing purposes windows firewalls have been turned off.

Trying to find a solution by only making changes to router 2.
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Yup, you've got a routing issue.

If you can't modify the routing table on Router 1, then you will need to add routes on the individual hosts.

Alternately, you can find out if Router 2 supports Proxy ARP, but I really, really do not like Proxy ARP.
FujiFrankAuthor Commented:
If I'm going to add routes to an individual host, what steps do I need to follow?

You mention Proxy ARP, this is something I'm not familiar with, what are the benefits and/or risks.

Getting a chance to get back at this, so I'm eager for some help.
Checking on DD-WRT, it doesn't look like it will support proxy arp, or if it does nobody has a guide on how to do it, so I don't think we should pursue that.

Adding routes is OS-specific.  For windows, you open the command prompt and enter the command like so:
route add <destination> mask <mask> <gateway> -p

that will add a route persistently, so you don't have to re-add the route each time you reboot.


route add mask -p
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FujiFrankAuthor Commented:
Ok, from looking at DD-WRT information I could not find anything reliable about Proxy Arp, so this is not a path I'm going to pursue.

Now adding as route I can follow but want to make sure I'm clear on the correct addresses.

Host A, is on Router 1 network and needs to be able to communicate with a host behind router 2. I understand the command line but want to make sure I'm doing it correctly.

route add <IP address Range of Host Connected to Router 2> mask <IP Address assigned to Router #2>

Would that be correct?

I have done that and when I run a trace route it goes to router #2 but then stops. Do I need to add something to router 2 iptables to make sure it routes the traffic correctly?

I'm getting closer but need a little more help.
Yes, that command is correct.

And yes, you need to make sure that router 2 isn't blocking the traffic.

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FujiFrankAuthor Commented:
Great help, got me on the right track.

You were able to confirm the path I needed to go and I have resolved my issue.

Thank you very much!
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