Nortel Networks NN46110-602 - Manual (Page 90)

90 Chapter 4 Troubleshooting
NN46110-602
You must create a connection definition for your initial Internet link through your
service provider. A separate connection definition is needed for creating the PPTP
tunnel. A common configuration problem experienced during initial PPTP setup is
the failure to select the PPTP VPN adapter (instead of the modem) on the PPTP
connection definition in Dialup Networking.
What DNS and WINS servers do I set for the dial-up
connection?
There is no need to set these servers statically on your dial-up client because
information is dynamically downloaded from the VPN Router for PPTP, IPsec,
and Layer 2 Forwarding (L2F) tunnels at connect time.
Why does DNS resolve hosts to different addresses when a
tunnel connection is active?
Cause: When a tunnel connection is activated, additional DNS servers are
downloaded from the extranet device to your client. In the case of Microsoft
Windows 95, Windows 98, and Windows NT operating systems, the new DNS
servers are added to the list of DNS servers that were assigned by your ISP. This
applies to PPTP as well as IPsec tunnels. In general, the DNS servers downloaded
by the extranet device provide host-name-to-address translation for hosts within a
private network while the ISP-based DNS servers translate public host names.
For Windows 95/98 and Windows NT, when a host name must be translated to an
IP address (for example to browse the Web or get e-mail), all DNS servers are
queried in a shotgun style. The first server to respond with an IP address wins.
This can produce some interesting behavior if a host name resolves to one address
on the private network and another on the public Internet. For example, host
mail.mycompany.com could internally resolve to 10.0.0.282 and externally to
146.113.64.231.
Action: To avoid problems when using a mixture of internal and external DNS
services, it is essential to avoid using names that resolve to different addresses. In
the preceding example, rename the host 10.0.0.282 to pop.mycompany.com. Then
users are informed to use the hostname pop.mycompany.com to retrieve electronic
mail, whether in the office or connected through a tunnel link.The original retail
release of Windows 95 requires the Winsock DNS Update (wsockupd) to properly
function with multiple DNS servers.