[Vpn-help] Routing and IP address assignment questions

Marc Goldburg mgoldburg at assia-inc.com
Wed Oct 17 20:18:16 CDT 2007


I'm using the Shrewsoft v2.0.1 Windows client (on WinXP) to connect to a 
Linksys RV042 (v1.3.8.2) firmware.  The tunnel establishes reliably, but 
IP packet routing is not reliable.  Only certain hosts on the subnet 
behind the router are visible to the client (e.g., via ICMP ping) and 
only certain TCP/UDP protocols work well to those hosts (e.g., for one 
of the machines behind the RV042, SIP and telnet from the client work 
reliably, but not http).

I've looked at the routing tables on the router and at the netstat -r 
and ipconfig  outputs on the client to try to debug this, but I'm not 
sure what the "correct" output looks like.  Answers to the following 
would be greatly appreciated (apologies in advance for the long list).

- When the client is configured with "use an existing adapter and 
current address" for its address method, should the routing table on the 
router have an entry for the client's nominal IP address when the tunnel 
is up?  Or does the router do something similar to NAT/PAT for the IP 
address of the client on the interface to its LAN-side subnet, so that 
traffic between the client and machines on the router's LAN-side subnet 
has the IP address of the router's LAN-side interface rather than the 
client's?

- When the client is configured with "use a virtual adapter and assigned 
address" for its address method:

1) if the virtual client address is on the subnet on the LAN-side of the 
router, how do other machines on the subnet know how to send traffic 
destined for the client to the router?  Does the router do a proxy ARP 
for the virtual client IP address?

2) when the client is set to "obtain automatically" the assigned address 
for the virtual adapter (a) does it do this via DHCP and (b) can the 
DHCP server be a device on LAN-side subnet of the router other than the 
router itself?  Currently, when I bring the tunnel up with "use a 
virtual adapter ..." for the address method, ipconfig on the local 
machine shows the virtual hardware address (aa:aa:aa:aa:aa:00 if I 
recall correctly), but no assigned IP address.

Thanks.
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