Two Gateways in Network Configuration - Backup gateway is always active
I have a customer who has two links to the Internet. One is a cable connection (Bright House Networks) and the other is a T1 (Megapath). A Windows 2003 server is doing DHCP. In the DHCP configuration the client computers get two gateways for failover. The primary gateway is the cable connection and the second/backup is the T1. This works great for all Windows XP machines. If the cable goes down, they all switch over to the T1 and then back again when the cable is back up and the IP address is renewed on the client. However, on the one Windows 7 Professional computer they are testing, the Internet connection is always the T1. When doing an IPCONFIG, the cable gateway shows first, but it doesn't make a difference. This is driving the customer crazy since he needs the speed of the cable for downloads. Yes, we could easily configure a static network setting, which would eliminate the T1, but then there goes the redundancy. Also, he wants to roll out Windows 7 to his network (50 computers) without changing anything and thereby retaining the redundancy. Anyone know what is going on here? Thanks, Tony
April 20th, 2010 12:09am

Hi Tony, This issue should be related to the multi-homed network configuration. Based on my research, I would like to share the following with you: Source IP address selection on a Multi-Homed Windows Computer Default Gateway Configuration for Multihomed Computers Hope this helps. Thanks. Nicholas Li - MSFT
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April 23rd, 2010 10:13am

Nicholas, Thank you for your reply. I was unaware you had answered my question until just recently. Your links for information on multi-homed computers were interesting but not relevant to the issue. I failed to point out in my original post that there is only one NIC in the computer. With the dual gateway configuration, we are attempting to use dead gateway detection to fail over to the second ISP connection. A link contained in the second article you cited lead me to knowledge base article 128978, which references dead gateway detection. I checked the registry setting to ensure dead gateway detection is enabled and it appears to be although it seems to use a different key title - DeadGWDetectDefault - instead of EnableDeadGWDetect, which is mentioned in the article. Are my assumptions correct or does a registry entry with a key title of EnableDeadGWDetect need to be added? Below is an IPCONFIG of the subject computer showing one NIC with two gateways. Windows IP Configuration Host Name . . . . . . . . . . . . : TUNAVAMPIRE Primary Dns Suffix . . . . . . . : dean.lcl Node Type . . . . . . . . . . . . : Hybrid IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No DNS Suffix Search List. . . . . . : dean.lcl Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : Description . . . . . . . . . . . : Intel(R) 82567LF-2 Gigabit Network Connection Physical Address. . . . . . . . . : 00-1C-C0-8F-E4-96 DHCP Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes Link-local IPv6 Address . . . . . : fe80::4962:459c:8736:4229%2(Preferred) IPv4 Address. . . . . . . . . . . : 192.168.1.87(Preferred) Subnet Mask . . . . . . . . . . . : 255.255.255.0 Lease Obtained. . . . . . . . . . : Monday, May 17, 2010 10:58:41 AM Lease Expires . . . . . . . . . . : Tuesday, May 25, 2010 10:58:34 AM Default Gateway . . . . . . . . . : 192.168.1.1 192.168.1.254 DHCP Server . . . . . . . . . . . : 192.168.1.205 DHCPv6 IAID . . . . . . . . . . . : 218111168 DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-11-35-D7-E1-00-1C-C0-8F-E4-96 DNS Servers . . . . . . . . . . . : 192.168.1.200 192.168.1.205 65.32.1.65 66.80.130.23 Primary WINS Server . . . . . . . : 192.168.1.205 NetBIOS over Tcpip. . . . . . . . : Enabled
May 24th, 2010 6:00pm

Even if you get this to work, it does not work as you expect. Yes, dead gateway detection should switch over if one connection fails. But there is no mechanism to switch back when the faster gateway becomes available again. It will only try to switch back if the gateway in use dies. To effectively manage two Intertnet connections you need a hardware device which can load balance two Internet connections. Bill
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May 25th, 2010 4:01am

Dead gateway detection actually works quite well at the client's location. All the Windows XP Professional workstations go out the cable connection until it goes down. When that happens, the computers switch to the T1. The network administrator automatically restarts every computer each night using a script I gave him. When the computers restart, they once again renew their IP addresses and then go out the cable connection as long as the cable ISP has fixed their network outage. The problem is, on the one Windows 7 Professional workstation, it will not use the cable connection (default gateway 192.168.1.1 om the IPCONFIG listing above) under any circumstances. It always goes out the the T! (192.168.1.254 gateway), and nobody seems to know why this happens or how to fix it. The issue is stalling a Windows 7 roll-out. It's hard to convince the client he needs new routers to support failover when the current system with Windows XP works exactly like he wants it to work. Tony
May 25th, 2010 4:16am

So, I guess no one has any idea on this post? Perhaps, someone might suggest another place to post. I would really like to find out why Windows 7 acts differently than Windows XP as it relates to dead gateway detection. Not only is this client not going to upgrade until this is resolved, but there is another client configured the same way who may face the same issue soon. Tony
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June 6th, 2010 8:11pm

Tony, were you able to figure this out? I am in the same situation. I have two internet connections, 10.0.0.1 & 10.0.0.2 and want to setup a server to use the .2 as failover when .1 goes down, then revert back when it is restored. Any info you found out would be appreciated. Thanks.
March 31st, 2011 1:36pm

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