Multiple Default Gateways for Failover Redundancy

hello,

we have two internet lines coming into our office from two different
providers.
i want to utilize both lines in order to create some form of failover
redundancy.
my idea was to use two routers with different LAN IPs (on the same subnet).
- ISP line 1 --> Router 1 --> 192.168.1.1 (LAN default gateway 1)
- ISP line 2 --> Router 2 --> 192.168.1.2 (LAN default gateway 2)
then give each computer two default gateways.
this way if one of the connections is down, the other one will be used:

is this a realistic approach?
I have read so many contradicting opinions I don't know what to believe!

our LAN has Win2003/2008 and WinXP
there is only one LAN, not multiple LANs or fancy routing etc.

thanks
christos

"Christos Kritikos" <(E-Mail Removed)> wrote in
message news351C632-7F0C-4904-96A4-(E-Mail Removed)...
> hello,
>
> we have two internet lines coming into our office from two different
> providers.
> i want to utilize both lines in order to create some form of failover
> redundancy.
> my idea was to use two routers with different LAN IPs (on the same
> subnet).
> - ISP line 1 --> Router 1 --> 192.168.1.1 (LAN default gateway 1)
> - ISP line 2 --> Router 2 --> 192.168.1.2 (LAN default gateway 2)
> then give each computer two default gateways.
> this way if one of the connections is down, the other one will be used:
>
> is this a realistic approach?
> I have read so many contradicting opinions I don't know what to believe!
>
> our LAN has Win2003/2008 and WinXP
> there is only one LAN, not multiple LANs or fancy routing etc.
>
> thanks
> christos
>

A better idea would be to buy a router which is capable of handling two
public connections. You can then use both ISP lines and share the load
across them. Using dead gateway detection to switch from an inactive line is
very limited (and it won't automatically switch back when the first line
recovers).

Hello Christos,

Do not assign multiple default gateways to a client. Use Dual port routers
for that.

http://support.microsoft.com/kb/159168

http://support.microsoft.com/kb/157025

Best regards

Meinolf Weber
Disclaimer: This posting is provided "AS IS" with no warranties, and confers
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> hello,
>
> we have two internet lines coming into our office from two different
> providers.
> i want to utilize both lines in order to create some form of failover
> redundancy.
> my idea was to use two routers with different LAN IPs (on the same
> subnet).
> - ISP line 1 --> Router 1 --> 192.168.1.1 (LAN default gateway 1)
> - ISP line 2 --> Router 2 --> 192.168.1.2 (LAN default gateway 2)
> then give each computer two default gateways.
> this way if one of the connections is down, the other one will be
> used:
> is this a realistic approach?
> I have read so many contradicting opinions I don't know what to
> believe!
> our LAN has Win2003/2008 and WinXP
> there is only one LAN, not multiple LANs or fancy routing etc.
> thanks
> christo

"Christos Kritikos" <(E-Mail Removed)> wrote in
message news351C632-7F0C-4904-96A4-(E-Mail Removed)...
> hello,
>
> we have two internet lines coming into our office from two different
> providers.
> i want to utilize both lines in order to create some form of failover
> redundancy.
> my idea was to use two routers with different LAN IPs (on the same
> subnet).
> - ISP line 1 --> Router 1 --> 192.168.1.1 (LAN default gateway 1)
> - ISP line 2 --> Router 2 --> 192.168.1.2 (LAN default gateway 2)
> then give each computer two default gateways.
> this way if one of the connections is down, the other one will be used:

Doesn't work worth a crap. Buy a firewall device with duel WAN ports that
is designed for this purpose.

Here is the DFG behavor:

128978 - Dead Gateway Detection in TCP/IP for Windows NT
http://support.microsoft.com/default...b;EN-US;128978

171564 - TCP/IP Dead Gateway Detection Algorithm Updated for Windows NT
http://support.microsoft.com/default...b;EN-US;171564

175767 - Expected Behavior of Multiple Adapters on Same Network
http://support.microsoft.com/default...b;EN-US;175767

159168 - Multiple Default Gateways Can Cause Connectivity Problems
http://support.microsoft.com/kb/159168/EN-US/

157025 - Default Gateway Configuration for Multihomed Computers
http://support.microsoft.com/default...roduct=win2000

Default gateways
http://www.microsoft.com/technet/pro...d3859f5b1.mspx

Default Gateway Behavior for Windows TCP/IP
http://www.microsoft.com/technet/com...uy/cg0903.mspx