[pptp-server] Metrics don't seem to work on NT 4.0?

Mason, Doug dmason at littler.com
Mon Nov 27 20:26:39 CST 2000


Without boring the list to death:

Goal: Have users in remote office use PPTP to connect to home office but use
a metric (or anything else?) to "fail over" to an existing frame connection
in the same office.

Environment: Remote office has an existing (slow) frame connection back to
the home office.  Remote office also has DSL connection.

PPTP is set up between the remote office and the home office via DSL and can
route traffic in between these two sites.

All users in remote office are set to have the default gateway be the PPTP
server.  Everything works well, the frame connection is never touched.

However, I thought I could just use a Metric in NT 4.0 and set it so that if
the VPN connection was unavailable it would bounce traffic back over to the
frame connection (which is a router).

10.65.1.1	Router on the frame connection
10.65.1.2	PPTP server via DSL to home office (255.255.0.0)
10.7.1.65	Address of remote office connection on the home office PPTP
server
10.7.1.1		Main router in home office

Sooo....

0.0.0.0		0.0.0.0	10.7.1.1		VPN_INTERFACE	10 (metric)
0.0.0.0		0.0.0.0	10.7.1.1		10.65.1.1		20

....what I would THINK this would do is that traffic would normally all go
via the VPN interface.  If the VPN interface is unavailable (ie: DSL dies)
the higher cost metric would become active and it would forward all the
traffic to the 10.65.1.1 router.

In actual testing, however, this doesn't seem to work.  It seems like NT
will keep the original route around and never bring up the second route.  If
I switch the matrix numbers around it will start moving via the Frame
instead of the DSL, but I can't get one to fail over to the other.  Printing
out the route table shows everything correctly and lists both routes with
the correct metric.

Am I using metrics in the wrong way or is it just not supported?

Surely other people are set up a VPN connection with a backup route in case
it goes down....?

Help!

--Doug Mason (dmason at littler.com)



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