Wrong route?

[Schellevis]

Hi,

A strange problem:

A test-pc has IP 192.168.10.101 subnetmask 255.255.255.0 it makes a VPN connection to network 192.168.0.x subnet 255.255.255.0 via ADSL. The local gateway (an ADSL router) has IP 192.168.10.1. So far everything is ok, I can ping a server (192.168.0.7) on the other end, I even can access the server via Windows Explorer. The routing table (ROUTE PRINT) looks ok, no references whatsoever to 192.168.0.x.

But .....

When I start Filemaker-client on the test-pc, I connect to the Filemaker-server 192.168.0.7, I see all the available databases, but after opening and after a while (say after 5 openened databases) Filemaker says "Network Error"! Trying to open the databases again fails, I can't even see them anymore.

I found out that someone (?) has added a wrong route-statement in the table (host 192.168.0.7 subnet 255.255.255.255 via router 192.168.10.1). I can get it working again by deleting (ROUTE DEL) the wrong line, disconnecting and then reconnect the VPN.

I tried to run the 'ROUTE DEL 192.168.0.7'-command in a loop, just as a test, and 3 out of 4 times it worked, very slow, but it works.

What is going on?

Thanx, Bas.

[adrien]

normally when routes appear like this, they are caused by ICMP redirects, or ICMP error messages caused by sending full-sized packets over a reduced-MTU link. the MTU (Max Transmission Unit) is the biggest size packet that will go over an interface.

Because of the encryption in WinGate VPN packets, we must reduce the MTU for a VPN tunnel down from 1500 to about 1440. To get around this we use ICMP error packets to tell client and server software (where they are set to use Path MTU discovery) how big packets they can send.

The OS on Win2k and later remembers this by creating a route.

You aren't running 5.0.8 or 5.0.9 are you? I thought I fixed this in 5.0.10

Adrien

[Schellevis]

normally when routes appear like this, they are caused by ICMP redirects, or ICMP error messages caused by sending full-sized packets over a reduced-MTU link. the MTU (Max Transmission Unit) is the biggest size packet that will go over an interface.

Because of the encryption in WinGate VPN packets, we must reduce the MTU for a VPN tunnel down from 1500 to about 1440. To get around this we use ICMP error packets to tell client and server software (where they are set to use Path MTU discovery) how big packets they can send.

The OS on Win2k and later remembers this by creating a route.

You aren't running 5.0.8 or 5.0.9 are you? I thought I fixed this in 5.0.10

Adrien

You hit the jackpot, Adrien!

I tried to set the MTU to 1400 and it works! It's pretty slow over our 512/1500 ADSL-line with (much slower in comparison with an direct 64K ISDN-line), but I'll guess a bit of twaeking and tuning will do the trick.

Any tips on this?

The client is running x.10, but the server-side is definitly older.

Thanks, Bas.