1 Modem, 2 Routers, Same Network

April 11, 2005 at 16:36:07
Specs: Win XP Pro, PIII 750 MHz / 384MB

Here is the setup I have:

Cable Modem - > Switch1 Port 1
WRT54G WAN -> Switch1 Port5
BEFSR11 WAN -> Switch1 Port4
WRT54G LAN1 -> Switch2 Port24
BEFSR11 LAN -> Switch2 Port23

LAN - WRT54G (192.168.1.1)
LAN - BEFSR11 (192.168.1.2)

Basically I want to get 2 IPs from my provider and use 1 (WRT54G) for traffic internal to access the internet and 1(BEFSR11) for external traffic to access me remotly (FTP, HTTP, etc.). The WRT54G does the DHCP on the network. I also have a server setup static. This sems to work but I've found something that doesn't quite work. During the setup I tried to use the BEFSR11 as the gateway to access the internet and it does not work. This is a static setup with a valid IP from my network. I can ping internally as well as browse the network. I thought it might be the DNS server so here are my ping results:

Gateway = 192.168.1.2
DNS Server = 192.168.1.2
C:\...\John>ping www.google.ca
Ping request could not find host www.google.ca. Please check the name and try again.

Gateway = 192.168.1.2
DNS Server = 192.168.1.1
C:\...\John>ping www.google.ca
Pinging www.l.google.com [64.233.167.104] with 32 bytes of data:

Request timed out.

It seems that with the DNS at 192.168.1.2 it can't even resolve the host, and with the DNS at 192.168.1.2 it resolves, but is still unable to reach it. Any idea what would cause this. The BEFSR11 doesn't have any DNS settings or anything. I need a PC to be able to use this router to access the internet so that I can use a PC to resolve its IP to a dynamic address. Any help would be great.



See More: 1 Modem, 2 Routers, Same Network

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#1
April 11, 2005 at 22:40:44

Right off the bat, this is a typo, so correct it.

"It seems that with the DNS at 192.168.1.2 it can't even resolve the host, and with the DNS at 192.168.1.2 it resolves, but is still unable to reach it. "

The following is exactly what would be expected.

"Gateway = 192.168.1.2
DNS Server = 192.168.1.2
C:\...\John>ping www.google.ca
Ping request could not find host www.google.ca. Please check the name and try again.

This is expected because you use BEFSR11 (192.168.1.2) as DNS server but don't tell it where to forward DNS requests! How in the heck do you expect it to know who google.com is? It doesn't and has to be programmed who to ask. If you are going to tell the computers to use this router as DNS server, then configure it with your ISPs DNS servers IPs to forward lookup requests to.

Now about why it won't connect. *Assuming* cable is similar in this respect to ADSL - a major, but likely, assumption, you can't connect two routers to the one Internet connection. Again, I am making an assumption, but for starters how would a packet coming in from the Internet know which router was handling it? So I think the assumption is safe and you can't do this.

I think in your topology you would need *two* cable connections, but there are other ways to do this. One is to get a router that supports DMZ (if yours don't) and simply put the remote access computer(s) on it. The router should also have mapping from public to private (WAN to LAN) addresses. If it doesn't and the remote server Internet name is not critical, you could use a free dynamic DNS service to do the mapping. You would enter the IP number on their configuration interface rather than use dynamic software on the computer or router, because the IP will never change anyway. Then use port forwarding to send the http, ftp, etc. packets to the right server. I do this myself.

Peter


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#2
April 12, 2005 at 15:43:42

*TYPO UPDATE*
It seems that with the DNS at 192.168.1.2 it can't even resolve the host, and with the DNS at 192.168.1.1 it resolves, but is still unable to reach it.
*TYPO UPDATE*

My cable provider does provide up to 3 IPs. Both routers are getting valid IPs and BOTH are receiving DNS and GATEWAY information from my ISP through the auto configuration.

I hope this helps.


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#3
April 12, 2005 at 19:06:33

>My cable provider does provide up to 3 IPs.

That doesn't necessarily mean they can be used on separate routers. My ISP does to, but just one is assigned to the ADSL (in my case) connection. Eight others are avaiable for WAN<->LAN mapping.

> Both routers are getting valid IPs

Same or different?

Peter


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