This article explains the tools and tasks in troubleshooting the IPv6 connectivity in Windows.
The major steps involved in the troubleshooting are:
- Verifying IPv6 connectivity.
- Verifying the reachability
- Verifying router reliability and managing the IPv6 routing table.
- Verifying Windows IPv6 based TCP connections.
To verify the current Windows IPv6 settings for an appropriate address configuration, we can use ipconfig /all in the command prompt of windows. It displays the IPv6 addresses, DNS servers and default routers for all the interfaces.
We can also use the Netstat tool. It displays active TCP connections, Ethernet statistics, the Ports on which a node is listening, the IPv6 routing table and IPv6 statistics (ICMPv6, TCP over IPv6, and UDP over IPv6 protocols).
The following figure shows the display of the Netstat tool on a computer running Windows Server 2008 / Vista:
In order to verify the reachability with a local or remote destination, we need to check and flush the neighbor cache. The recently resolved link-layer addresses are stored in the neighbor cache. We use the netsh interface ipv6 show neighbors command to view the contents of neighbor cache. The figure below displays the contents:
In case of missing or incorrect routes in the IPv6 routing table, it is not possible to reach the local or remote destination. We need to ensure that we have a route corresponding to the local subnet. If it is automatically configured with a default router then we have a default route. The netsh interface ipv6 add route command should be used to add a route to IPv6 routing table and netsh interface ipv6 set route command is used to modify an existing route. To view the routing table of IPv6, we use the netstat r, or netsh interface ipv6 show route command.
In case of router performance issues, we use pathping d IPv6Address command. This command traces the path to the destination and displays the information regarding the packet losses of all the routers.
The netsh interface ipv6 show route command displays the list of routes in the routing table. The figure below displays the contents:
To check whether a TCP connection could be established using the destination TCP port number of the application, we generally use the telnet IPv6Address TCPPort command.
Thus, the article illustrates the troubleshooting of IPv6 connectivity with the relevant snapshots.
