Networking computers with 2 ISP

Posted on 2003-11-11
Last Modified: 2013-11-30
I have a two DSL lines coming in, each DLS line comes with 5 static ip's.

DSL1-connects to a Sonic Wall router wich connects to Win2k server pc.

DSL2-connects to a Lynksys router that has 4 computers connected to it, all running windows XP pro.

How can I get the computers behind the lynksys router to network with the computer behind the sonic router??????.

feel free to e-mail any diagrams to

Question by:gusquiroz
LVL 31

Expert Comment

ID: 9725550
Have each router "own" a separate subnet.

Then, uplink the two routers to each other or to a common switch/hub

Then, set static routes between the two routers.


Sonic Wall owns 192.168.0.* ( mask  All computers connected to Sonic Wall are in the same 192.168.0.x range

LinksSys owns ( mask  All computers connected to LinkSys are in the same 192.168.1.x range

After setting that up, create a single network "segment" out of the two... if one has an Uplinjk port, connect it to a standard port on the other.  Or, use a crossover cable between two regular ports. or if you have none to spare, get a hub or switch, and connect it all up.

Now, technically they can route traffic to each other, they just don't "know that" So, on the Sonic Wall, set a static route to the LinkSys segment ( mask via the LinkSys address (

And, vice versa.


The only problem you might run into is DHCP conflicts.  I would turn one DHCP off, and set static addresses for teh boxes that used to se that DHCP.

Expert Comment

ID: 9725822
qwaletee, when we turn DHCP off, it does not matter Router is using static or Dynamic IP Address?

Lets say Router is getting a Dynamic IP Address.
and Dhcp is disabled.

so i can use a Static IP on my NIc, it should be no problem?

Author Comment

ID: 9726546

Can you draw a layout so I can get a visual, this will realy help.
e-mail it to the address provided.
LVL 31

Accepted Solution

qwaletee earned 400 total points
ID: 9727518
Don't confuse the router's dynamic IP with the internal DHCP.

Let's say I have a DSL line to Verizon, and my neighbor has a cable line to CableVision.  Each of us uses a cheap home router, and one PC connected to each.  There wold be four dynamically assigned IP addresses.  Suppose my router is a D-Link, and the neighbor's is an SMC.

CableVsion assigns external dynamic IP to the SMC in my neighbor's house.
The SMC provides DHCP within my neighbor's house, assigning his PC an IP address like
Verizon assigns my D-Link an external dynamic IP
D-Link provides DHCP dynamic address to my internal PC.

The D-Link has TWO places where you specify dynamic or static.  On teh ROUTER EXTERNAL ("WAN") port, I specify that it should obtain a dynamic address (in this case, a PPPoE address, similar to DHCP).  And teh router by default has a DHCP server turned on for the INTERBAL ports ("LAN").  I can turn off that DHCP server without affecting the external WAN address.  Or, if I switch to a DSL provider that allows static IP addresses, then I can leave DHCP on internally, while changing from PPoE dynamic address to a static WAN address.

You have a similar setup... your two routers have external dynamic addresses from teh broadband providers, and are set up to request their addresses from teh provider.  They are also providing DHCP services for the internal computers, which is a separate system.  If you turn off the DHCP server, then the computers that used to get their addresses from the router wll no longer be able to do so; you will have to provide static IP setup on those computers instead.

Once you do that, you can put the two networks "on one wire" so to speak.

The truth is, you don't even need the static routes.  ou cold make the whole network one logical networks, with one IP address range.  Just put in different gateways for the appropriate computers.  If all PCs have addresses like 192.168.99.* and Sonic Wall was, and the Linksys was, then using a mask of, al the computers and routers would be able to talk to each oher directly, as long as they were effecitively on one physical LAN.  The only question is how each PC "gets to an outside address."  If you give one PC a gateway address, then that PC will always send internet traffic through the Sonic Wall -- it knows how to reach teh Sonic Wall (they share the same address space, 192.168.99.x), and with teh SOnic Wall's IP set as the gateway, it will request that the SOnic Wall forward all non-internal traffic for it.

Similarly, a second PC, if assigned a gateway address of instead of .1, it will request the Linksys to forward all traffic for it.

LVL 41

Expert Comment

ID: 9727623
Just an FYI, all solutions must e posted in the Question, e-mail can't be used as per the MA

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