[pptp-server] pptpd connection established - ping not working!

[Ron Cresswell]

Hi Folks, sorry about the length of this email but I figured it was 
preferable to have too much info than too little.

Two things (at least) not working on my connection at the moment. Doubt 
if they are related, but they might be.

Once the connection is established, I can't ping a machine behind the 
server, although I can ping the server quite happily (this is my current 
main concern)

Second, I am (for the moment) adding the routing tables by hand after 
the connection comes up, because the server end doesn't seem to be 
executing /etc/ppp/ip-up.local after the ppp link is established, even 
though that's what RedHat is supposed to do.

my connection is VPN-client (jabba) -> firewall (hades) -> internet -> 
firewall (cerberus) -> VPN-server (ghost). I am trying to ping from the 
VPN client to a machine in the subnet of the VPN server.

IP-forwarding is switched on on both VPN-client and VPN-Server, both of 
which are running a "server" install of RedHat 6.2. I am trying to 
connect two subnets (203.7.194.0/25 and 203.7.194.128/26) via the pptp link.

Now the routing tables look symmetric (see below), but if I try a 
traceroute from client machine to "machine in subnet of server" I get:

traceroute to zaphod.compumod.com.au (203.7.194.169), 30 hops max, 38 
byte packets
1  ghost-VPN.compumod.com.au (203.7.194.159)  451.431 ms  333.927 ms  
369.523 ms
2  * * *
3  * * *

Whereas, if I try a traceroute from the server machine to "machine in 
subnet of client" I get this:

traceroute to swami.compumod.com.au (203.7.194.30), 30 hops max, 38 byte 
packets
1  * * *

Does this make sense to anyone? It sounds as though the routing tables 
aren't right, but see below -

Once the link is up, my routing tables look like this:
On Jabba (the client):

Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
ghost-VPN.compu *               255.255.255.255 UH    0      0        0 ppp0
jabba           *               255.255.255.255 UH    0      0        0 eth0
ghost.compumod. hades.syd.compu 255.255.255.255 UGH   0      0        0 eth0
203.7.194.0     *               255.255.255.128 U     0      0        0 eth0
203.7.194.128   *               255.255.255.128 U     0      0        0 ppp0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         hades.syd.compu 0.0.0.0         UG    0      0        0 eth0

On Ghost (the server), the routing table looks like this:

Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
jabba.compumod. cerberus.compum 255.255.255.255 UGH   0      0        0 eth0
jabba-VPN.compu *               255.255.255.255 UH    0      0        0 ppp0
ghost.compumod. *               255.255.255.255 UH    0      0        0 eth0
203.7.194.0     *               255.255.255.128 U     0      0        0 ppp0
203.7.194.128   *               255.255.255.128 U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
default         cerberus.compum 0.0.0.0         UG    0      0        0 eth0

So my pptp IP addresses are on the local subnet (as recommended to get 
around the proxyarp problem, which I don't understand anyway so 
allocated ips on the local subnets) - jabba has an IP address of 
203.7.194.33 and its VPN ip address is 203.7.194.34. Simliar with ghost 
and ghost-VPN - 203.7.194.163 and 203.7.193.159.

an "ifconfig" on each box shows the following for the ppp0 connection:

on ghost

ppp0      Link encap:Point-to-Point Protocol 
         inet addr:203.7.194.159  P-t-P:203.7.194.34  Mask:255.255.255.255
         UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
         RX packets:114 errors:0 dropped:0 overruns:0 frame:0
         TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:10

on jabba:

ppp0      Link encap:Point-to-Point Protocol 
         inet addr:203.7.194.34  P-t-P:203.7.194.159  Mask:255.255.255.255
         UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
         RX packets:8 errors:0 dropped:0 overruns:0 frame:0
         TX packets:115 errors:0 dropped:0 overruns:0 carrier:0
         collisions:0 txqueuelen:10

I'm getting very close to abandoning pptp in favour of starting from 
scratch with another approach (although I don't really have time to do 
that either!). Any thoughts?

Ron