Q197205: RRAS IPX VPNs Generate Event ID 20124
Article: Q197205
Product(s): Microsoft Windows NT
Version(s): WinNT:4.0
Operating System(s):
Keyword(s):
Last Modified: 12-JUL-2001
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The information in this article applies to:
- Microsoft Routing and Remote Access Service Update for Windows NT Server version 4.0
- Microsoft Windows NT Server version 4.0
- Microsoft Windows NT Server, Enterprise Edition version 4.0
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IMPORTANT: This article contains information about editing the registry.
Before you edit the registry, make sure you understand how to restore it if
a problem occurs. For information on how to do this, view the "Restoring
the Registry" online Help topic in Regedit.exe or the "Restoring a Registry
Key" online Help topic in Regedt32.exe.
SYMPTOMS
========
When your client computers try to access resources across a Routing and Remote
Access (RRAS) Point-to-Point Tunneling Protocol (PPTP) tunnel routing IPX, your
RRAS server will log the following error:
Event ID 20124
Source: IPXRIP logs with the following description:
Description: Another IPX router claims different network number for
interface <ipxvpn>.
Offending router IPX address is in the data.
RRAS will also stop forwarding IPX and SAP.
CAUSE
=====
The IPX stack sees that a packet from the clients LAN is trying to go over the
WAN adapter and it then uses this network number of the client as the autonet
value for the adapter. The network number is incorrect and will cause routing to
stop.
RESOLUTION
==========
If you receive event ID 20124, you will need to disable the ability of RRAS to
use unnumbered WAN connections.
You can make this change by editing the following registry entry.
WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee that
problems resulting from the incorrect use of Registry Editor can be solved. Use
Registry Editor at your own risk.
For information about how to edit the registry, view the "Changing Keys And
Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete
Information in the Registry" and "Edit Registry Data" Help topics in
Regedt32.exe. Note that you should back up the registry before you edit it. If
you are running Windows NT, you should also update your Emergency Repair Disk
(ERD).
1. Run Registry Editor (Regedt32.exe).
2. Go to the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RemoteAccess
\Parameters\Ipx
NOTE: The above registry key is one path; it has been wrapped for readability.
3. On the Edit menu, click Add Value and use the following entry (if the entry
already exists, just double-click it to edit the value):
Value Name: EnableUnnumberedWanLinks
Data Type: REG_DWORD
Value range: 0 - 0xFFFFFFFF
Default value: 1
By default, this value is 1. Change this value to 0.
MORE INFORMATION
================
Consider the following environment:
Lclient LRRAS ===== VPN ===== RRRAS Rclient
eeee ddcc ccbb aaaa
| ipx | | IP only | | ipx |
-----dddd----- -cccc-X-----X-cccc- -----bbbb-----
Both RRAS servers (LRRAS and RRRAS) have two network cards.
On LRRAS, one network card is configured with IPX only (net ID dddd) and the
other network card is configured with IPX (net ID cccc) and an IP address on the
10.0.0.0/8 network. The internal network ID is configured to be ddcc. The X in
the diagram represents IPX outbound filters (drop all) and IP outbound filters
(allow only PPTP).
On RRRAS, one network card is configured with IPX only (net ID bbbb) and the
other network card is configured with IPX (net ID cccc) and an IP address on the
10.0.0.0/8 network. The internal network id is configured to be ccbb. The X in
the diagram represents IPX outbound filters (drop all) and IP outbound filters
(allow only PPTP).
The filters assure that IPX traffic will only flow over the PPTP tunnel created
between the two RRAS servers.
Lclient and Rclient only have IPX bound to their NICs and have internal network
IDs defined as eeee and aaaa respectively.
On the RRAS servers, both RIP and SAP have been configured on the LAN and WAN
interfaces.
As soon as client eeee tries to view client aaaa, the VPN adapter on LRRAS
changes the net ID of the WAN interface from all zeroes (the default) to eeee,
which RRRAS cannot handle. It logs error 20124 and stops routing IPX packets.
Event ID 20124
Source: IPXRIP logs with the following description:
Description: Another IPX router claims different network number for
interface <ipxvpn>.
Offending router IPX address is in the data.
After the above error is logged, IPX routing is stopped and both RIP and SAP
timeout over the PPTP connection.
Additional query words: rras ipx 20124
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Keywords :
Technology : kbWinNTsearch kbWinNT400xsearch kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400 kbWinNTS400xsearch kbWinNTS400 kbAudDeveloper kbRRASNTSearch kbRRASNT400
Version : WinNT:4.0
Issue type : kbprb
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