Windows 2000 DHCP option 003 two router IP's

Posted on 2006-04-06
Medium Priority
Last Modified: 2010-04-13
We have two T1's in different buildings. We are going to connect the two buildings with fiber optic cable, but I would still like to make use of the T1 in the other building. I noticed you can add multiple routers in the 003 DHCP option. Are there any performance issues with doing this, or is there a way to add a metric in the DHCP options. I am thinking about changes my scope to include the both the and 103.1 subnets. Exclude the 103.1 from the scope, and using this as a redundant gateway in the event our primary T1 fails. Has anyone done this, and knows that it will work? Are there any known performance issues with doing this?
Question by:Rodney Barnhardt
LVL 71

Accepted Solution

Chris Dent earned 500 total points
ID: 16393065

You can have multiple default Gateways on Windows machines and it will act as a failover in the event of the first gateway going down.

For the implementation I've done of this we had one gateway with a higher metric so the second connection would only ever be used in the event of the first failing. The changover itself is surprising neat and it normally takes a couple of minutes at the most for client machines to realise, if the first gateway becomes available again clients will simply switch back automatically.

Remember that whatever you do the Default Gateway has to be on a directly attached network for it to work.

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Author Comment

by:Rodney Barnhardt
ID: 16393727
Now we have two seperate routers and two seperate firewalls. Is there a way to set the metric in the DHCP server options? I realize if both T1 came to the same location I could set the metric on the router or the firewall. I did not notice a setting in the DHCP options to set a metric.
LVL 78

Expert Comment

by:Rob Williams
ID: 16414631
If stuck, you could use a batch file or add to logon script something similar to the following, to set the metric:

netsh interface ip set address name = "Local Area Connection" gateway = gwmetric = 1

I would assume this would work, as the logon script would run after DHCP has assigned the IP and gateway, and this would simply update the TCP/IP configuration. However, I don't know if it would retain the metric if the user were to stay logged in longer than the DHCP lease time, and a new lease were issued.

Just food for thought.

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