Getting at a machine behind a ISDN router

[Carlos Sousa]

I'm trying to connect 2 machines:

1) "server": my home machine, has a public IP, firewalled with iptables

2) "client": machine at the school I work at as sysadmin, private IP,
behind a ISDN router connected to the Internet through their ISP.

Since there is no way I can access the school machine from the home one,
I thought a vpn between the two could enable me to do that.

I installed and configured tinc on both machines, but I cannot ping from
any side. When I try to connect from "client" to "server", the tinc logs
at "server" show:

   Received UDP packet from unknown source 194.210.6.254 port 756

This address seems to be the dynamic IP of the ISDN router. It seems that
the firewall / masquerading on the router is confusing tinc. Is that right?

Is there anything I can do on either machine to get the vpn going,
without having to change anything on the router or on the school's ISP
side?

And another question: the "client" machine host file cannot have an
Address= option, since it has no public IP assigned. Is this OK with tinc?

Thanks for any help.

-- 
Carlos Sousa
http://vbc.dyndns.org/

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