Two Default Gateways

I have a question. I thought I would be able to do this without any problems
but apparently there is something stopping it from working.

I have a T1 line whose router is configured with NAT. It is set as the
default gateway for the network. IP - 192.168.x.1
I also have a DSL modem configured with NAT. IP - 192.168.x.2

I have connected both of these to the network as follows

Router \
> Switch < The rest of the internal network.
DSL Modem /

We have many outside computers which connect to our server via RDP to run a
program. They all connect via the Router's (T1's) Public IP which has port
forwarding through to the server's private IP.

Occasionally, the T1 goes down and I need to have them connect via the
backup DSL's public IP. I thought that I could have both router and DSL
attached and the clients could use either IP to connect but, if the T1 is
functional, only that interface works. If the T1 goes down, the DSL will
begin working. Is there any way for them both to work simultaneously? Why
won't the DSL modem forward the ports through when the T1 is up? I thought
this would be pretty straight forward but there must be something which is
blocking the DSL port forwarding when the T1 is functional. Any suggestions
would be greatly appreciated.

Thanks.

You may need to a dual WAN router. This search result may help,

what isWhat is Dual WAN or Load Balance Router? What is svchost.exe? What is the Group Policy Management Console? Previous Page Next Page. Related Topics ...
http://www.howtonetworking.com/whatis/whatis.htm


Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com
"Steve Martin" <(E-Mail Removed)> wrote in message news:eU0%(E-Mail Removed)...
I have a question. I thought I would be able to do this without any problems
but apparently there is something stopping it from working.

I have a T1 line whose router is configured with NAT. It is set as the
default gateway for the network. IP - 192.168.x.1
I also have a DSL modem configured with NAT. IP - 192.168.x.2

I have connected both of these to the network as follows

Router \
> Switch < The rest of the internal network.
DSL Modem /

We have many outside computers which connect to our server via RDP to run a
program. They all connect via the Router's (T1's) Public IP which has port
forwarding through to the server's private IP.

Occasionally, the T1 goes down and I need to have them connect via the
backup DSL's public IP. I thought that I could have both router and DSL
attached and the clients could use either IP to connect but, if the T1 is
functional, only that interface works. If the T1 goes down, the DSL will
begin working. Is there any way for them both to work simultaneously? Why
won't the DSL modem forward the ports through when the T1 is up? I thought
this would be pretty straight forward but there must be something which is
blocking the DSL port forwarding when the T1 is functional. Any suggestions
would be greatly appreciated.

Thanks.

This you can easily accomplish by using Cisco ASA 5505 which is the smaller
model and has an OK pricetag

--
----------------------------------------------------------------------------------------------------------------------------
Johan Engdahl
CCSA, CCSE, CCA, MCP | johan AT firewall1 DOT nu | http://www.firewall1.nu


"Steve Martin" <(E-Mail Removed)> wrote in message
news:eU0%(E-Mail Removed)...
>I have a question. I thought I would be able to do this without any
>problems but apparently there is something stopping it from working.
>
> I have a T1 line whose router is configured with NAT. It is set as the
> default gateway for the network. IP - 192.168.x.1
> I also have a DSL modem configured with NAT. IP - 192.168.x.2
>
> I have connected both of these to the network as follows
>
> Router \
> > Switch < The rest of the internal network.
> DSL Modem /
>
> We have many outside computers which connect to our server via RDP to run
> a program. They all connect via the Router's (T1's) Public IP which has
> port forwarding through to the server's private IP.
>
> Occasionally, the T1 goes down and I need to have them connect via the
> backup DSL's public IP. I thought that I could have both router and DSL
> attached and the clients could use either IP to connect but, if the T1 is
> functional, only that interface works. If the T1 goes down, the DSL will
> begin working. Is there any way for them both to work simultaneously? Why
> won't the DSL modem forward the ports through when the T1 is up? I thought
> this would be pretty straight forward but there must be something which is
> blocking the DSL port forwarding when the T1 is functional. Any
> suggestions would be greatly appreciated.
>
> Thanks.
>

It won't happen. Both lines have to go into the same device as the other
suggested. But a T1 and a DSL are two different Line Technologies and may not
work together.

There is no such thing as "port forwarding". That is a term invented by the SOHO
market when selling Home Users their Broadband Devices that they call "routers"
when they are not really routers either. The ports aren't doing anything and
nothing is being done to them,..the action that happens is at Layer3 and the
ports are at Layer4. The action is happening at the IP#s not the ports. Ports
are just Layer4 Addresses just like IP#s are Layer3 Addresses,..ports identify
the destination Application while the IP#s identify the destination Host.

The term for what your T1 Router is doing is called StaticNAT (aka ReverseNAT)
and that has nothing to do with what you want to do with the two lines.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
-----------------------------------------------------

"Steve Martin" <(E-Mail Removed)> wrote in message
news:eU0%(E-Mail Removed)...
>I have a question. I thought I would be able to do this without any problems
>but apparently there is something stopping it from working.
>
> I have a T1 line whose router is configured with NAT. It is set as the default
> gateway for the network. IP - 192.168.x.1
> I also have a DSL modem configured with NAT. IP - 192.168.x.2
>
> I have connected both of these to the network as follows
>
> Router \
> > Switch < The rest of the internal network.
> DSL Modem /
>
> We have many outside computers which connect to our server via RDP to run a
> program. They all connect via the Router's (T1's) Public IP which has port
> forwarding through to the server's private IP.
>
> Occasionally, the T1 goes down and I need to have them connect via the backup
> DSL's public IP. I thought that I could have both router and DSL attached and
> the clients could use either IP to connect but, if the T1 is functional, only
> that interface works. If the T1 goes down, the DSL will begin working. Is
> there any way for them both to work simultaneously? Why won't the DSL modem
> forward the ports through when the T1 is up? I thought this would be pretty
> straight forward but there must be something which is blocking the DSL port
> forwarding when the T1 is functional. Any suggestions would be greatly
> appreciated.
>
> Thanks.
>

Thanks for the suggestion on the Cisco. I checked it out and it is a little
outside of the budget for this particular client. I purchased a D-link
DI-LB604 though which I am hoping will do the trick.

"Johan Engdahl" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> This you can easily accomplish by using Cisco ASA 5505 which is the
> smaller model and has an OK pricetag
>
> --
> ----------------------------------------------------------------------------------------------------------------------------
> Johan Engdahl
> CCSA, CCSE, CCA, MCP | johan AT firewall1 DOT nu | http://www.firewall1.nu
>
>
> "Steve Martin" <(E-Mail Removed)> wrote in message
> news:eU0%(E-Mail Removed)...
>>I have a question. I thought I would be able to do this without any
>>problems but apparently there is something stopping it from working.
>>
>> I have a T1 line whose router is configured with NAT. It is set as the
>> default gateway for the network. IP - 192.168.x.1
>> I also have a DSL modem configured with NAT. IP - 192.168.x.2
>>
>> I have connected both of these to the network as follows
>>
>> Router \
>> > Switch < The rest of the internal network.
>> DSL Modem /
>>
>> We have many outside computers which connect to our server via RDP to run
>> a program. They all connect via the Router's (T1's) Public IP which has
>> port forwarding through to the server's private IP.
>>
>> Occasionally, the T1 goes down and I need to have them connect via the
>> backup DSL's public IP. I thought that I could have both router and DSL
>> attached and the clients could use either IP to connect but, if the T1 is
>> functional, only that interface works. If the T1 goes down, the DSL will
>> begin working. Is there any way for them both to work simultaneously? Why
>> won't the DSL modem forward the ports through when the T1 is up? I
>> thought this would be pretty straight forward but there must be something
>> which is blocking the DSL port forwarding when the T1 is functional. Any
>> suggestions would be greatly appreciated.
>>
>> Thanks.
>>
>
>

I do appreciate the education. To me they are ports regardless of what layer
they are on. I may be naming them incorrectly, but at least you and others
understood what I meant. But again, I do appreciate the education. I have a
pretty good knowledge of how to get things working but when it comes to the
technical terms and the deeper workings, I don't know yet so your post helps
me get there a little more. As they say, you learn something new every day.
I guess now I can go to bed.

"Phillip Windell" <@.> wrote in message
news:OaQYl$(E-Mail Removed)...
> It won't happen. Both lines have to go into the same device as the other
> suggested. But a T1 and a DSL are two different Line Technologies and may
> not work together.
>
> There is no such thing as "port forwarding". That is a term invented by
> the SOHO market when selling Home Users their Broadband Devices that they
> call "routers" when they are not really routers either. The ports aren't
> doing anything and nothing is being done to them,..the action that happens
> is at Layer3 and the ports are at Layer4. The action is happening at the
> IP#s not the ports. Ports are just Layer4 Addresses just like IP#s are
> Layer3 Addresses,..ports identify the destination Application while the
> IP#s identify the destination Host.
>
> The term for what your T1 Router is doing is called StaticNAT (aka
> ReverseNAT) and that has nothing to do with what you want to do with the
> two lines.
>
> --
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
> The views expressed (as annoying as they are, and as stupid as they
> sound), are my own and not those of my employer, or Microsoft, or anyone
> else associated with me, including my cats.
> -----------------------------------------------------
>
> "Steve Martin" <(E-Mail Removed)> wrote in message
> news:eU0%(E-Mail Removed)...
>>I have a question. I thought I would be able to do this without any
>>problems but apparently there is something stopping it from working.
>>
>> I have a T1 line whose router is configured with NAT. It is set as the
>> default gateway for the network. IP - 192.168.x.1
>> I also have a DSL modem configured with NAT. IP - 192.168.x.2
>>
>> I have connected both of these to the network as follows
>>
>> Router \
>> > Switch < The rest of the internal network.
>> DSL Modem /
>>
>> We have many outside computers which connect to our server via RDP to run
>> a program. They all connect via the Router's (T1's) Public IP which has
>> port forwarding through to the server's private IP.
>>
>> Occasionally, the T1 goes down and I need to have them connect via the
>> backup DSL's public IP. I thought that I could have both router and DSL
>> attached and the clients could use either IP to connect but, if the T1 is
>> functional, only that interface works. If the T1 goes down, the DSL will
>> begin working. Is there any way for them both to work simultaneously? Why
>> won't the DSL modem forward the ports through when the T1 is up? I
>> thought this would be pretty straight forward but there must be something
>> which is blocking the DSL port forwarding when the T1 is functional. Any
>> suggestions would be greatly appreciated.
>>
>> Thanks.
>>
>
>

I am surprised by three things;
one that you have a modem talking directly to your network with no nat or
firewall protection and
two that nobody mentioned why this is a serious problem and
three you haven't been hacked or DoS attacked because of this setup.

"Stevie Wonder" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I do appreciate the education. To me they are ports regardless of what layer
>they are on. I may be naming them incorrectly, but at least you and others
>understood what I meant. But again, I do appreciate the education. I have a
>pretty good knowledge of how to get things working but when it comes to the
>technical terms and the deeper workings, I don't know yet so your post helps me
>get there a little more. As they say, you learn something new every day. I
>guess now I can go to bed.

Ok. Good luck with it.

Sometimes I am the "English Teacher from Hell",...but it is for good reason.
I also write my posts knowing that the one I am writing to isn't the only one
reading it. Without correct terminology all you have is chaos. Ever since the
explosion of the Home User market the industry has been in total chaos over
terminology because they let Marketing Departments who don't know what they are
talking about start using terms however they felt like it to try to get the
"uneducated" home user to buy their products.

Understanding the correct terminology, ...almost by itself, ...will teach you
how things work. That is why all the text books for technical stuff begin by
teach that first.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
-----------------------------------------------------

"Joshua Bolton" <(E-Mail Removed)> wrote in message
news:38C095D5-98C5-4B99-B0C0-(E-Mail Removed)...
>I am surprised by three things;
> one that you have a modem talking directly to your network with no nat or
> firewall protection and
> two that nobody mentioned why this is a serious problem and
> three you haven't been hacked or DoS attacked because of this setup.

I didn't mention it because that isn't what I belive is really there. He is just
misusing the terms. What he calls a DSL Modem is really a NAT
Device,...probably a broadband device with the modem built into the same "box".
On the T1, the router there would be a "real" router and it is configured to run
NAT as well. So he has, ...at least in a very basic sense,...a NAT-based
Firewall on each line.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed (as annoying as they are, and as stupid as they sound), are
my own and not those of my employer, or Microsoft, or anyone else associated
with me, including my cats.
-----------------------------------------------------

Yes, both devices are "NATing". The DSL modem is a modem/router/wireless
access point. I know I'm not the smartest in the world, but I'm not THAT
dumb. I can't wait for the DI-LB604 to arrive so I can get this all setup
and tested. In fact, with the price being so low, I am considering adding
another ISP for my home office and adding my own DI-LB604. We are purely on
VoIP here so it is a pain when our Internet goes down.

"Phillip Windell" <@.> wrote in message
news:(E-Mail Removed)...
> "Joshua Bolton" <(E-Mail Removed)> wrote in message
> news:38C095D5-98C5-4B99-B0C0-(E-Mail Removed)...
>>I am surprised by three things;
>> one that you have a modem talking directly to your network with no nat or
>> firewall protection and
>> two that nobody mentioned why this is a serious problem and
>> three you haven't been hacked or DoS attacked because of this setup.
>
> I didn't mention it because that isn't what I belive is really there. He
> is just misusing the terms. What he calls a DSL Modem is really a NAT
> Device,...probably a broadband device with the modem built into the same
> "box". On the T1, the router there would be a "real" router and it is
> configured to run NAT as well. So he has, ...at least in a very basic
> sense,...a NAT-based Firewall on each line.
>
> --
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
> The views expressed (as annoying as they are, and as stupid as they
> sound), are my own and not those of my employer, or Microsoft, or anyone
> else associated with me, including my cats.
> -----------------------------------------------------
>
>