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“Top 10 RAS Problems Solved” is a historical troubleshooting article about Microsoft Remote Access Service (RAS)—the dial-up networking technology used with Windows NT 3.5/3.51 and related 1990s clients. Published by ITPro Today on December 31, 1995, it covers ten problems ranging from routing and remote-share access to modem compatibility. Its procedures are useful for understanding legacy systems, not as instructions for Windows 10 or 11, current Windows Server, or modern VPNs.
Read the original article at ITPro Today. The bylines and date are also reflected in the authors’ archive listings for Roy Seabourne and Thomas Ollerenshaw.
The ten problems at a glance
| # | Symptom | Main issue | Historical context |
|---|---|---|---|
| 1 | LAN clients cannot reach the Internet through an NT dial-up machine | Routing and addressing | Two interfaces, separate subnets, and a return route were required. |
| 2 | TCP/IP stops working after an NT 3.51 upgrade | Duplicate addressing | The article identifies the same IP address on the NIC and RAS link as the cause. |
| 3 | Traffic leaves through the wrong interface | Route selection | A RAS PhoneBook default-gateway setting altered which path was used. |
| 4 | Manual login is needed for a third-party PPP or SLIP service | Login scripting | NT RAS could use a SWITCH.INF script to respond to prompts. |
| 5 | A dial-up connection works, but remote shares say “Access Denied” | Authentication and authorization | Dial-in credentials did not automatically grant file-share access. |
| 6 | Remote servers do not appear in the browser | Discovery and naming | Browsing could fail even when a direct share connection was possible. |
| 7 | Windows for Workgroups 3.11 reports RAS Error 640 | Memory, drivers, or modem setup | Low conventional memory was identified as a common cause. |
| 8 | Local NetWare servers disappear after connecting over IPX | Legacy NetWare discovery | The redirector could switch between separate bindery environments. |
| 9 | RAS software compression does not interoperate | Client/server version compatibility | Some combinations required specific service packs or system files. |
| 10 | An unlisted modem will not connect reliably | Hardware and driver compatibility | Emulation, a manufacturer script, or a custom modem entry might help. |
The original article is a useful snapshot of 1990s networking and support practice. Its file names, registry settings, modem workflows, and commands are specific to old operating systems; do not transplant them into a current Windows installation.
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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minute1. Routing LAN traffic through an NT RAS client
Symptom: An NT computer connects to an Internet provider by dial-up, but other computers on its local network cannot use that connection.
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The setup described has two interfaces: a network card on the LAN and a PPP or SLIP dial-up link. The article says each interface needs its own address and the LAN and dial-up networks must be distinct, non-overlapping subnets. LAN clients must use the NT machine’s LAN-interface address as their gateway. That alone is not enough: the far-end PPP/SLIP server also needs a route back to the LAN, or replies cannot find their way home.
For its NT 3.5x scenario, the article lists enabling routing with IPEnableRouter=1, setting DisableOtherSrcPackets=0, and leaving the LAN card without a default gateway. These are historical registry settings, not current Windows guidance. Its important enduring point is that forwarding requires correct addressing, a forward path, and a return path—not simply a successful dial-up connection.
Security context: The original warns that services and shares on LAN machines could become reachable through an Internet-connected RAS gateway. A gateway changes exposure, so services need deliberate access controls. The article’s recommendation to stop services is specific to its period; modern systems should be secured using current network and service controls.
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The article attributes this problem to assigning the same IP address to the LAN network card and the RAS PPP connection. It describes that as invalid TCP/IP configuration and says an earlier NT 3.5 RAS bug had allowed the arrangement to appear to work; NT 3.51 exposed it. That explanation is the article’s account of the period, not a general diagnosis for modern upgrade failures.
The historical correction was to give the interfaces distinct addresses, or, where appropriate, disable TCP/IP binding to the NIC. The RAS PhoneBook option Use default gateway on remote network could also matter to the desired route. The broader lesson is to check for duplicate addresses and unintended routes whenever a multi-interface machine behaves differently after a software change.
3. Traffic uses the wrong interface
On the NT RAS client described, the PhoneBook option Use default gateway on remote network affected where non-local traffic went. With it enabled, traffic for the local subnet stayed on the LAN while traffic for other networks used the remote gateway. With it disabled, destinations not on the RAS link could be sent through the local network card instead.
Where a remote connection needed to reach another local subnet, the original gives this NT 3.51 example:
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsRoute ADD 199.199.40.0 MASK 255.255.255.0 199.199.41.1 /PHere /P made the route persistent in that version. Treat this as an archival example only: the addresses are illustrative, and the command and behavior belong to old Windows NT. Before changing a route on any system, identify the destination network, next hop, and intended default gateway.
4. Automating a third-party PPP or SLIP login
Some dial-up servers expected a sequence of prompts before starting PPP or SLIP. NT RAS could automate that exchange with a script stored in SWITCH.INF, selected in the RAS PhoneBook security settings under After Dialing. The script could wait for a username prompt, send a username, wait for a password prompt, and choose the protocol.
A redacted illustration of the old pattern is:
COMMAND=
OK="UserName:"
COMMAND=<username>
OK="Password:"
COMMAND=<password>
OK="PPP or SLIP:"
COMMAND=PPPThis is not a current Windows component or recommended login method. In particular, scripts that store passwords in readable text expose credentials. The sample is schematic; prompt spelling and script syntax depended on the server and the legacy RAS implementation.
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5. “Access Denied” despite a successful dial-up connection
A successful RAS login established permission to connect to the remote-access service; it did not necessarily grant permission to open a file share. The article distinguishes credentials used for dial-in from the account used to access network resources. Share permissions and the identity presented to the remote server still applied.
Its period-specific options included logging on with the remote-network credentials while leaving the RAS link active, creating a local account with matching credentials, or specifying an account explicitly when connecting to a share. One historical command example is:
net use * \srcsvrspec /u:MyDomainMyNameThe durable diagnostic distinction is between connectivity, remote-access authentication, and authorization to a particular resource. A working connection does not prove the user has share permissions. The command syntax and account behavior above are from the NT-era article, not a complete current Windows sign-in guide.
6. Remote servers are missing from network browsing
The article says that browsing remote servers through File Manager depended on membership in a valid remote workgroup or domain; joining a domain also required a machine account there. Yet failure to browse did not necessarily mean the server was unreachable. A user could try a direct UNC path in the form \ServerNameShareName, with a domain-qualified account if required.
This distinction remains useful when interpreting the old case: discovery and direct access are separate. In the article’s environment, legacy browsing depended on network and domain mechanisms that are not a template for modern discovery or identity systems.
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7. RAS Error 640 on Windows for Workgroups 3.11
For this specific 16-bit Windows environment, the article identifies insufficient conventional memory as the most common cause of Error 640. Its advice was to reduce memory-consuming drivers and terminate-and-stay-resident programs, and to move suitable components into upper memory. It also lists other possibilities: a modem selected incorrectly, a cable missing required pin connections, a connection speed too high for line quality, software-compression problems, or a conflicting virtual communications driver.
The source mentions editing CONFIG.SYS and AUTOEXEC.BAT, changing the [386Enh] section of SYSTEM.INI, and using DEVICE=*VCD in one driver-related workaround. These are strictly historical troubleshooting details. Error numbers and remedies vary by product and version; none of these edits should be treated as a fix for a current Windows error. The article also notes a possible interaction between logging on to a target domain over a NIC and then connecting to it through RAS.
8. Local NetWare access disappears after an IPX RAS connection
In the article’s NetWare scenario, the IPX connection could cause the redirector to use a remote server bindery for name-to-address resolution, disrupting access to local NetWare servers. The historical workaround was to reach NetWare through Gateway Services for NetWare on an NT machine, or to use NetBEUI for the RAS client rather than IPX.
IPX, NetBEUI, bindery-based discovery, and Gateway Services for NetWare are obsolete technologies. This case is valuable for understanding why a client could lose access when its network context changed, not as a modern network configuration recommendation.
9. Software-compression compatibility between RAS versions
The article describes RAS software compression across NT 3.5x and clients including Windows for Workgroups 3.11, NT 3.1, and Windows 95. Compatibility depended on the exact server and client combination. It says an NT 3.5 RAS server needed Service Pack 2 for the described scenario, while NT 3.51 did not need that additional server update. It also names client components—RASMAC.386 for Windows for Workgroups 3.11 and ASYNCMAC.SYS for NT 3.1—and says Windows 95 Dial-Up Networking used the same scheme without an extra step in that case.
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Those names identify historical components, not files to download and install today. Replacing system files from an unverified source can create security and stability risks; the article’s version-specific compatibility notes should be used only to interpret an appropriately preserved legacy system.
10. A modem is missing from the NT Hardware Compatibility List
An unlisted modem might still work, but the article makes no guarantee. Its suggestions were to select a supported model the modem emulated, try the generic Hayes Compatible 9600 entry, use a manufacturer-provided RAS script, or add a section to MODEM.INF based on an existing entry after backing up the file.
Emulation could be a compromise: a generic driver might connect while failing to expose a device’s full speed, error correction, or compression features. These were NT-era modem configuration paths; they are not instructions for configuring modern broadband, cellular connections, or current Windows dial-up stacks.
What remains useful in the article
The ten cases cover more than a faulty modem. They illustrate a practical way to classify connectivity failures:
- Addressing: Look for duplicate IP addresses and overlapping subnets.
- Routing: Check the selected gateway, specific routes, and whether replies have a return path.
- Authentication and authorization: Separate permission to connect from permission to use a share or other resource.
- Naming and discovery: A missing browser listing does not by itself prove that direct access is impossible.
- Compatibility: Protocol negotiation, drivers, modems, cables, line quality, and client/server versions can all matter.
- Resources: On older systems, memory limits could prevent networking from working at all.
- Security: Connecting a gateway to an external network can expose services that were previously reachable only locally.
What not to copy into a modern setup
Do not apply the article’s NT 3.5x registry values, persistent-route syntax, SWITCH.INF or MODEM.INF edits, DEVICE=*VCD setting, IPX/NetBEUI recommendations, service-pack assumptions, or legacy system-file replacements to a modern machine without authoritative, version-specific documentation. The article predates current Windows releases, contemporary VPN architectures, and modern security practices. It is best read as an archival account of how Microsoft RAS troubleshooting worked in its time.
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