Setting up a user for PPTP

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5.4.2 Configuring PPTP on an Ascend MAX 4004

On the Ascend MAX 4000 line, PPTP was first released on the firmware revision 4.6Bi12. The typical Ascend MAX 4004 configuration supports four T1 or PRI lines and 48 digital modems. Unlike the U.S. Robotics switch, the only way to specify PPTP servers is on a per- line basis, where each line is a WAN interface. On a MAX 1800, these will be BRI ISDN lines, while on a MAX 4004, theyll be T1 or PRI lines. This can be a serious limitation for ISPs that want to provide PPTP services to clients from various companies, all of whom will have different RAS servers. We expect Ascend to change this in the future to support these ISPs. For a company providing dial-up services to a single NT domain, however, this should pose no problem. Note that the MAX forwards all authentication on a PPTP-configured line to the RAS server, so a PPTP user wont have to be entered in a configuration profile or RADIUS profile on a MAX. Here are the steps for configuring PPTP on the Ascend MAX 4004: 1. From the main Edit menu, select Ethernet Mod Config PPTP options. 2. Under the PPTP options menu, turn PPTP on by changing the PPTP Enable option to Yes with the Enter key. Enter a PPTP host for at least one of the Route line parameters. If you only want a certain line to handle PPTP calls, just enter an IP address for that line. The other lines, left as the default of 0.0.0.0, will handle calls normally. However, if you enable PPTP and leave all lines at 0.0.0.0, the MAX will treat all calls as PPTP calls and the MAX will no longer accept any incoming calls—it will stop routing and be functionally disabled. For our example, all four of our PRI lines will use the same PPTP host of 1.1.1.60 see Figure 5-11 . Figure 5-11. The PPTP line configuration screen on an Ascend MAX 4004 3. Press the Escape key and select to accept the changes and exit in order to save the new PPTP information to the MAXs nonvolatile RAM.

5.5 Making the Calls

When calling into an ISP that supports PPTP, all of the VPN work is done for you by the ISP on their remote access switch. You just have to configure your client as if youre dialing directly into your RAS server; the ISPs switch will pass all the authentication information to that RAS server. 84 When dialing into an ISP that doesnt support PPTP, youll need to initiate a PPP call to the ISP using the Dial-Up Networking dialog box. Once the call has been connected, leave your PPP session up, select the PPTP entry you made in our case, its called Central Office VPN, and click the Dial button. This will initiate the PPTP call to the corporate RAS server over your PPP Internet connection.

5.6 Troubleshooting Problems

What do you do if your system doesnt connect? Is the trouble with your remote users ISP, the Central Offices ISP, with the Internet itself, or with the configuration on the RAS client or server? Because of all the factors involved, problems with VPN connections are some of the most difficult to track down.

5.6.1 Login problems

For dial-up RAS users, the most common problem in getting connected is working with the modem. In that case, all troubleshooting can be done on the client side. Authentication problems bad usernames or passwords, or incorrect authentication type follow shortly thereafter, and often require that someone look through the logs or watch the connection attempt at the destination RAS server. Windows NTs Event Viewer and Dial-Up Networking Monitor help you isolate such login problems.

5.6.1.1 The Event Viewer

The Event Viewer is the common logging system on all Windows NT machines. It can be found from the Start menu under Programs Administrative Tools. Lets say that Sara N. is having trouble dialing in—she seems to be having negotiation problems and isnt sure why. When you bring up the Event Viewer, look at the Source column for any RemoteAccess messages that occurred at the approximate time she was attempting to dial in. In the left-hand column, there are icons that distinguish informational messages an i encircled in blue, from warning messages an exclamation mark encircled in yellow, and from error messages a red STOP sign. You see a red STOP sign with the Source of RemoteAccess at the time Sara N. was attempting to dial in. Double-clicking on it will reveal the full error message see Figure 5-12 . The error appears to stem from a DHCP negotiation problem. The next logical step would be to make sure Sara N. is set up to obtain an IP address using DHCP, and to ensure that your DHCP server is configured correctly.