Document ID: 15002
Contents
Introduction
Prerequisites
Requirements
Components Used
Background Information
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Introduction
This document discusses duplicate network addresses in IPX networks.
Prerequisites
Requirements
There are no specific requirements for this document.
Components Used
This document is not restricted to specific software and hardware versions.
Background Information
Quite a few of our product support calls for LAN²LAN concern duplicate network addresses. You cannot duplicate network addresses in an IPX network if you want it to work smoothly. If you do have duplicate network addresses, you expect to easily see the effects. However, this is not always the case.
When you connect previously separated networks using LAN²LAN, it is quite common for duplicate network addresses to show up at that time. This usually happens because the installer has taken care that real network addresses are not duplicated but has overlooked the server internal addresses.
NetWare v3.x Servers have an IPX internal address, and NetWare v2.x Servers can be configured as non-dedicated, in which case they are assigned a network address for the non-dedicated DOS partition.
If you have just joined two previously distinct Internets with LAN²LAN, and users on one side can log in across LAN²LAN but not vice versa, this is our suggested approach to diagnosing the problem. Enter a Display Networks command on each router and server in the Internet and copy down the results on a sheet of paper. Here is an example of such a list:
Table: Display Networks Sample Sheet --------------------------------------------------------------- Server_North <-- LAN²LAN --> Router_South Server_South =============================================================== 1 1/6 1 0/1 1 0/1 2 0/1 B01 0/5 B01 1/6 10 0/1 2 1/2 2 0/1 B01 0/1 10 1/2 10 2/3 ---------------------------------------------------------------
The first figure is the network number and the x/y figure is the hop/tick count to get there from here. Ignore the tick counts and concentrate on the hop counts. Note that a hop count of zero indicates a locally connected network. So Server_North has three locally connected networks, one of which, #2, is the internal IPX network. Router_South has two locally connected networks, all of which are external. Server_South has two locally connected networks one of which, #2, is internal for the non-dedicated DOS function.
When written down like this it is easy to see that network #2 is duplicated.
The effect of this is that workstations on the South network that try to attach or log in to Server_North are correctly told to go to net #2 to find Server_North, but anything they try to send to Net #2 is routed to Server_South, where it is misunderstood and rejected.
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| Updated: Oct 06, 2005 | Document ID: 15002 |