Most Microsoft exams expect you to have some troubleshooting knowledge and exam 70-291 is not exception. You need to be able to troubleshoot TCP/IP addressing problems as well as DHCP issues. So let’s take a look at some of the common problems that you can expect to be tested on.

When it comes to troubleshooting IP addressing, you need to know the different utilities that are available. Know that the ipconfig command can be used to view IP configuration information. There are a number of different parameters that can be used with the command as listed below.

• /all Displays detailed IP configuration information
• /release Releases the IP address for the specified adapter
• /renew Renews the IP address for the specified adapter
• /flushDNS Purges the entries in the DNS cache
• /registerDNS Refreshes all leased IP addresses and re-registers DNS names
• /displayDNS Displays the contents of the DNS cache

Another utility that is useful in troubleshooting IP addressing problems is ping. You need to know the process that you go through with the ping command to diagnose IP communication problems.

1. Ping the loopback address of 127.0.0.1 to ensure TCP/IP is initialized on the local computer.
2. If successful, ping the IP address assigned to the local computer.
3. Next ping the IP address of the default gateway. If this fails verify that the IP address of the default gateway is correct and that the gateway is operational.
4. Next ping the IP address of a host on a remote network. If this is unsuccessful, verify that the remote host is operational, verify the IP address of the remote host, and verify that all routers and gateways between the local computer and remote computer are operational.

As I discussed in a previous article, authorizing a DHCP server is an extremely important topic. If the DHCP service in a server will not start, one of the first things you should check is that the server has been authorized. Also, if you are unable to authorize a DHCP server, make sure that you are a member of the Enterprise Admins group.

Multiple DHCP servers can exist on a network. However you may encounter problems if you have a DHCP server configured as a standalone server and a DHCP server configured as a member server on the same subnet. Once the stand-alone server detects the second DHCP server it will attempt to verify with a domain controller that it is authorized. Since the stand-alone server is not a member of the domain, it will fail to contact a domain controller and stop servicing DHCP client requests. To resolve the problem, the authorized DHCP server must be removed from the subnet.

Scope problems can also occur. Remember that scope options can be configured at different levels. If you configure the 004 router option at the server level and there are multiple subnets, some clients may not be able to communicate outside of their local subnet. So always verify that scope options are correctly configured.

Remember when troubleshooting DHCP that you can also use the System log in Event Viewer and the DHCP Server audit log to diagnose and resolve issues.