barbary Posted November 30, 2006 Share Posted November 30, 2006 I have two gateways lets call them A and B. If I define both as default gateways and give A a metric of 1 and B a metric of 2. Then create EnableDeadGWDetect in the registry and set it to 1. (Amazing that none of the technotes that talk about dead gateway tell you it isn't on by default. Even though there is a technote to discribe how to switch it on in the registry) I then unplug A from the wall and try and surf to a web page. It Fails over and uses Gateway B a tracert confirms it. I then plug A back in and unplug B. It goes back to using Gateway A ONCE. After it has done this once the computer will never do it again. Any ideas why? Link to comment https://www.neowin.net/forum/topic/517332-dead-gateway-detection/ Share on other sites More sharing options...
+BudMan MVC Posted November 30, 2006 MVC Share Posted November 30, 2006 How long did you wait after it switch back to gateway A, before you killed it again? The system has had to have time to detect that gateway B was back online .. Even if it was back online, the machine will not switch back to it unless it has figured out that was working again. Link to comment https://www.neowin.net/forum/topic/517332-dead-gateway-detection/#findComment-588095618 Share on other sites More sharing options...
barbary Posted November 30, 2006 Author Share Posted November 30, 2006 BudMan said: How long did you wait after it switch back to gateway A, before you killed it again? The system has had to have time to detect that gateway B was back online .. Even if it was back online, the machine will not switch back to it unless it has figured out that was working again. Actualy your on to something there. Although I was at this for 3 hours this morning and even forced it to use the working Gateway B so it had plenty of oppertunity to see Gateway B as working. Now that I have returned from lunch which makes it more than 6 hours since the first test it did work again. This time I rebooted to send it back to Gateway A and it appears to stay working. Strange though because this still isn't correct behaviour and it happyly goes from B back to A when B goes out even though it has yet to see if A is working. Microsoft says it should just go to the next gateway in the list nothing about needing to see it work. Anyway although it seems like a great feature with Gateway A constantly dropping within 15 minutes of working we all end up using the much slower Gateway B and then there is nothing apart from a reboot that will send you back to Gateway A. A proper load baring dual router is needed for a real soloution I guess. Link to comment https://www.neowin.net/forum/topic/517332-dead-gateway-detection/#findComment-588095711 Share on other sites More sharing options...
+BudMan MVC Posted November 30, 2006 MVC Share Posted November 30, 2006 How exactly were creating a failed gateway test? According to this -- http://www.microsoft.com/technet/community...guy/cg1105.mspx Fail-back Support for Default Gateway Changes In TCP/IP for Windows Server 2003 and Windows XP, when dead gateway detection changes the default gateway, the new default gateway remains the primary gateway for default route traffic until dead gateway detection switches to the next one in the list (cycling through the list of default gateways) or until the computer is restarted. Therefore, dead gateway detection in TC/IP for Windows Server 2003 and Windows XP provides a fail-over function, but not a fail-back function. The lack of fail-back for default gateways can cause throughput problems on a subnet containing two routers: a high-capacity primary router and a lower-capacity backup router. The hosts on the subnet have the high-capacity router as their first default gateway and the backup router as their second default gateway. If the high-capacity router has a temporary failure, hosts on the subnet will switch over to the backup router. When the high-capacity router becomes available again, none of the hosts on the network use it because they have switched to the backup router. The Next Generation TCP/IP stack provides fail-back for default gateway changes by periodically attempting to send TCP traffic through the previous gateway. If the TCP traffic sent through the previous gateway is successful, the Next Generation TCP/IP stack switches the default gateway to the previous gateway. In our example with the high-capacity router and backup router, if the neighboring high-capacity router becomes unavailable, the hosts on the subnet use Neighbor Unreachability Detection to switch their default gateways to the backup router. The hosts then periodically attempt to send TCP traffic through the high-capacity router. When the high-capacity router becomes available and the hosts determine that TCP traffic sent through the high-capacity router is successful, the hosts switch their default gateway back to the high-capacity router. Support for fail-back to primary default gateways can provide faster throughput by sending traffic through the primary default gateway on the subnet. -- How you were creating the failure might have something to do with what you were seeing.. But yes I would agree with a proper load balancing router would be solution than using dead gateway detection. Link to comment https://www.neowin.net/forum/topic/517332-dead-gateway-detection/#findComment-588096181 Share on other sites More sharing options...
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