DOD - - - - DOD / \ RRAS-A RRAS-B --- LAN 188.8.131.52 \ / LAN - - - - - - - - - - - - LAN 10.10.10.1 10.10.10.10In this scenario, it may be expected that if the local-area network (LAN) connection does not work for some reason, the Dial-On-Demand (DOD) connection will start. This is based on the idea that DGD should start once the first default gateway does not work. There are 2 static routes on RRAS-A:
destination net mask gateway interface metric 0.0.0.0 0.0.0.0 184.108.40.206 dod-test 220.127.116.11 0.0.0.0 10.10.10.10 NIC 2If a program on RRAS-A is running and is accessing 18.104.22.168, the path it takes is across 10.10.10.10 over the local area network (LAN) connection. With the preceding static routes, there is no problem as long as the LAN connection exists. However, if the LAN connection does not work, any further communication also does not work. Because of this, DGD is not activated and the DOD connection never dials.
DOD - - - - - RAS / \ LAN - - - RRAS/Proxy ISP - - Internet non-valid \ / IP address LAN - - -T1/other - - - LANIn this scenario, it may be expected that if the dedicated Internet Service Provider (ISP) connection for some reason does not work on the external side of the proxy server, the DOD connection starts. This is also based on the idea that DGD should start once the first default gateway does not work. The static routes that might be attempted may look like the following table:
destination net mask gateway interface metric 0.0.0.0 0.0.0.0 22.214.171.124 dod-isp 126.96.36.199 0.0.0.0 188.8.131.52 NIC 2When multiple default gateways are specified on the external side of a Microsoft Proxy 2.0-based server, it might be expected to provide redundant connections to the Internet through the dialup device or devices. But if the LAN based ISP connection does not work, any further communication also does not work. Because of this, DGD is not activated and the DOD never dials.
DOD - - - - - RAS / \ LAN - - - RRAS ISP - - Internet valid \ / IP address LAN - - -T1/other - - - LANThis scenario is very similar to scenario 2, but it does not work for a different reason. In this scenario, the LAN behind the RRAS server is using Internet-valid IP addresses. When clients are trying to pass outward through the RRAS server, if the LAN-based ISP connection does not work, the RRAS server never activates DGD and does not dial the DOD connection to the ISP. Note that this occurs even with the static routes in the following table:
destination net mask gateway interface metric0.0.0.0 0.0.0.0 184.108.40.206 dod-isp b 220.127.116.11 0.0.0.0 18.104.22.168 NIC 2The reason for this inability to fail-over is that DGD relies on TCP transmission in order to activate it. When an RRAS server is behaving as a router, as it is in this case, it never parses the IP packet beyond the IP layer. Instead, it determines if the packet should be routed, and then either routes the packet or drops the packet.
Article ID: 205027 - Last Review: 12/05/2015 10:41:36 - Revision: 3.0