Nortel Networks NN46110-602 manual Why are subnet masks important?

Chapter 4 Troubleshooting 87

To specify a computer as the preferred master browser, set the parameter for IsDomainMasterBrowser to True or Yes in the following registry path:

\HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Browser\ Parameters

Unless the computer is configured as the preferred master browser, the parameter entry is always False or No. There is no user interface for making these changes; you must modify the registry.

Why are subnet masks important?

If a client does not have a WINS server or is unable to contact it, it must broadcast a query to try to locate a host. Unfortunately, Windows 95, Windows 98, and Windows NT clients do not always use the correct broadcast address when tunneling.

The following example helps explain this problem. Suppose that you are using a private net 10 address space. Assume further that you have a client with IP address

10.1.2.3and subnet mask 255.255.0.0. This means that the net 10 space is used like a class B address space, which is perfectly legal. The correct broadcast for this client is 10.1.255.255. However, Microsoft clients can broadcast to 10.255.255.255, using the natural class A for net 10, in spite of their configuration.

If all hosts that the client is trying to reach lie on the same physical segment, this probably will work. This is because every host on the physical network receives the all subnets broadcast and probably responds, if appropriate.

All hosts on the segment receive the broadcast to 10.255.255.255, even if they are on different subnets (10.1.x.x. and 10.2.x.x). However, in a routed environment the situation changes. In this case, a broadcast from 10.1.2.3 to 10.255.255.255 is not forwarded to the other 10.2 subnet.

In the extranet environment, make the remote client appear as much as possible to be on the local LAN. If the extranet host is assigned address 10.1.2.3, it should behave as if it is on the 10.1 LAN.

Nortel VPN Router Troubleshooting