ZyXEL Communications ZyWALL 2 Plus - Manual (Page 288)

Chapter 14 IPSec VPN
ZyWALL 2 Plus User’s Guide
288
Figure 189 SECURITY > VPN > Global Setting
The following table describes the labels in this screen.
Table 74 SECURITY > VPN > Global Setting
LABEL DESCRIPTION
Output Idle Timer The ZyWALL disconnects a VPN tunnel if the remote IPSec router does not
reply for this number of seconds.
Input Idle Timer When no traffic is received from a remote IPSec router after the specified
time period, the ZyWALL disconnects the VPN tunnel. 0 disables the check
(this is the default setting).
The output idle timer never takes effect if you set this timer to a shorter
period.
Gateway Domain
Name Update Timer
This field is applicable when you enter a domain name to identify the
ZyWALL and/or the remote secure gateway.
Enter the time period (between 2 and 60 minutes) to wait before the ZyWALL
updates the domain name and IP address mapping through a DNS server.
The ZyWALL rebuilds the VPN tunnel if it finds that the domain name is now
using a different IP address (any users of the VPN tunnel will be temporarily
disconnected).
Enter 0 to disable this feature.
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.