ZyXEL Communications ZyXEL ZyWALL 2WG - Manual (Page 291)

Chapter 14 IPSec VPN
ZyWALL 2WG User’s Guide
291
14.17 Telecommuter VPN/IPSec Examples
The following examples show how multiple telecommuters can make VPN connections to a
single ZyWALL at headquarters. The telecommuters use IPSec routers with dynamic WAN IP
addresses. The ZyWALL at headquarters has a static public IP address.
14.17.1 Telecommuters Sharing One VPN Rule Example
See the following figure and table for an example configuration that allows multiple
telecommuters (A, B and C in the figure) to use one VPN rule to simultaneously access a
ZyWALL at headquarters (HQ in the figure). The telecommuters do not have domain names
mapped to the WAN IP addresses of their IPSec routers. The telecommuters must all use the
same IPSec parameters but the local IP addresses (or ranges of addresses) should not overlap.
Adjust TCP Maximum
Segment Size
The TCP packets are larger after the ZyWALL encrypts them for VPN. The
ZyWALL fragments packets that are larger than a connection’s MTU
(Maximum Transmit Unit).
In most cases you should leave this set to Auto. The ZyWALL automatically
sets the Maximum Segment Size (MSS) of the TCP packets that are to be
encrypted by VPN based on the encapsulation type.
Select Off to not adjust the MSS for the encrypted TCP packets.
If your network environment causes fragmentation issues that are affecting
your throughput performance, you can manually set a smaller MSS for the
TCP packets that are to be encrypted by VPN. Select User-Defined and
specify a size from 0~1460 bytes. 0 has the ZyWALL use the auto setting.
VPN rules skip
applying to the overlap
range of local and
remote IP addresses
When you configure a VPN rule, the ZyWALL checks to make sure that the
IP addresses in the local and remote networks do not overlap. Select this
check box to disable the check if you need to configure a VPN policy with
overlapping local and remote IP addresses.
Note: If a VPN policy’s local and remote IP addresses overlap,
you may not be able to access the device on your LAN
because the ZyWALL automatically triggers a VPN
tunnel to the remote device with the same IP address.
Apply Click Apply to save your changes back to the ZyWALL.
Reset Click Reset to begin configuring this screen afresh.
Table 90 SECURITY > VPN > Global Setting (continued)
LABEL DESCRIPTION