ZyXEL Communications 200 Series User Manual

Chapter 49 Troubleshooting

ZyWALL USG 100/200 Series User’s Guide

• If you have the ZyWALL and remote IPSec router use certificates to authenticate each 

other, make sure they trust each other’s certificates. If the ZyWALL’s certificate is self-
signed, import it into the remote IPsec router. If it is signed by a CA, make sure the remote 
IPsec router trusts that CA. The ZyWALL uses one of its Trusted Certificates to 
authenticate the remote IPSec router’s certificate. The trusted certificate can be the remote 
IPSec router’s self-signed certificate or that of a trusted CA that signed the remote IPSec 
router’s certificate.

V

I cannot set up an L2TP VPN tunnel.

1 Make sure you have configured L2TP correctly on the remote user computers. See 

 for examples.

2 Make sure you configured an appropriate policy route on the ZyWALL.
3 Make sure there is not a firewall or NAT router between the ZyWALL and the remote 

users.

4 Make sure the remote users are using public IP addresses. 

V

The VPN connection is up but VPN traffic cannot be transmitted through the 
VPN tunnel.

Routing policies define how the ZyWALL forwards packets to their destinations. You must 
create a policy route for the ZyWALL to route VPN traffic through a VPN tunnel to the 
remote network. 

The VPN wizard automatically creates a corresponding policy route. If you use the VPN > 
IPSec VPN or VPN > L2TP VPN screens to set up a VPN tunnel, you need to manually 
configure a policy route for the VPN tunnel.

V

I cannot download the ZyWALL’s firmware package.

The ZyWALL’s firmware package cannot go through the ZyWALL when you enable the anti-
virus Destroy compressed files that could not be decompressed option. The ZyWALL 
classifies the firmware package as not being able to be decompressed and deletes it. 

You can upload the firmware package to the ZyWALL with the option enabled, so you only 
need to clear the Destroy compressed files that could not be decompressed option while 
you download the firmware package. See 

 for more on the anti-

virus Destroy compressed files that could not be decompressed option.