How to use 2 Default Gateways

[ME]

I have two internet connections. One is a cable connection that guarantees
3mb down. The second is a dsl connect that guarantees 1.5 mb down. I want
the cable modem to act as the PRIMARY gateway with a metric 1. The dsl I
want as a backup for when the cable is down (comcast has some stability
issues...) So I want the dsl to be the SECONDARY gateway with a metric of
2. This works great on all my Windows 2000 Pro DHCP clients they
automatically switch as necessary.

The trouble is with my Windows 2000 DNS Server, which also acts as my RRAS
server and Domain Controller. I can not seem to get it to recognize that it
has 2 gateways, one with a metric of 1 and the other with a metric of 2.
Hence when the cable modem is down, DNS does not work, except for those
names that are already cached. In fact the entire server is completly off
the net when the cable modem goes down. I have tried manually adding the
routes at the command prompt, setting one as default in the TCP/IP
properties and the other as manual route in RRAS, and even tried leaving the
TCP/IP properties empty and setting the routes manually in RRAS. But to no
avail.

Does any one have any experience with this?

Thanks,

Matt

 

[Phillip Windell]

You can't have two Default Gateways. The Default Gateway is a "global
configuration" for the entire machine. By the very definition of the term
you can have only one.

157025 - Default Gateway Configuration for Multihomed Computers
http://support.microsoft.com/default.aspx?scid=kb;en-us;157025&Product=win2000

Using redundant routes is a feature of *real* routers where both "lines"
come into the same router. The router uses its own built in "fail over"
ability in combination with Routing Protocols to make this happen. All the
involved Routers on every end of every line must be configured to *work
together* to accomplish this.

Your network then uses the Router as the way out to the Net and is in no way
concerned with how "it happens" once the traffic hits the Router.

Now in the case of "Home User" links, which is what Cable Internet and DSL
*really* are designed for, I believe that there may be some SOHO Cable/DSL
routers that have inputs for two WAN links and can take care of the
"fail-over" within themselves. But you'll have to check on that
yourself,...I am not familiar with these types of devices.

 

[ME]

Phillip,

Thank you for the reply. Do have any explanation as why this would work on
the workstations then?

Thanks,

Matt

You can't have two Default Gateways. The Default Gateway is a "global
configuration" for the entire machine. By the very definition of the term
you can have only one.

157025 - Default Gateway Configuration for Multihomed Computers
http://support.microsoft.com/default.aspx?scid=kb;en-us;157025&Product=win2000

Using redundant routes is a feature of *real* routers where both "lines"
come into the same router. The router uses its own built in "fail over"
ability in combination with Routing Protocols to make this happen. All the
involved Routers on every end of every line must be configured to *work
together* to accomplish this.

Your network then uses the Router as the way out to the Net and is in no way
concerned with how "it happens" once the traffic hits the Router.

Now in the case of "Home User" links, which is what Cable Internet and DSL
*really* are designed for, I believe that there may be some SOHO Cable/DSL
routers that have inputs for two WAN links and can take care of the
"fail-over" within themselves. But you'll have to check on that
yourself,...I am not familiar with these types of devices.

--

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

I have two internet connections. One is a cable connection that guarantees
3mb down. The second is a dsl connect that guarantees 1.5 mb down. I want
the cable modem to act as the PRIMARY gateway with a metric 1. The dsl I
want as a backup for when the cable is down (comcast has some stability
issues...) So I want the dsl to be the SECONDARY gateway with a metric of
2. This works great on all my Windows 2000 Pro DHCP clients they
automatically switch as necessary.

The trouble is with my Windows 2000 DNS Server, which also acts as my RRAS
server and Domain Controller. I can not seem to get it to recognize

that

it
has 2 gateways, one with a metric of 1 and the other with a metric of 2.
Hence when the cable modem is down, DNS does not work, except for those
names that are already cached. In fact the entire server is completly off
the net when the cable modem goes down. I have tried manually adding the
routes at the command prompt, setting one as default in the TCP/IP
properties and the other as manual route in RRAS, and even tried leaving the
TCP/IP properties empty and setting the routes manually in RRAS. But to no
avail.

Does any one have any experience with this?

Thanks,

Matt

 

[Phillip Windell]

Thank you for the reply. Do have any explanation as why this would work on
the workstations then?

I suspect it isn't working the way you think it is, and what is really
happening isn't what you think. You have ginve me virtually no configuration
information for me to make a call on that.