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Chapter 15 IPSec VPN Screens
ZyWALL 2WG User’s Guide
324
15.7 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.
15.7.1 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.
Local and Remote IP
Address Conflict
Resolution
Select
The Local Network
to send packets destined for overlapping local
and remote IP addresses to the local network (you can access the local
devices but not the remote devices).
Select
The Remote Network (via VPN Tunnel)
to send packets destined for
overlapping local and remote IP addresses to the remote network (you can
access the remote devices but not the local devices.)
If the remote IPSec router also supports NAT over IPSec, it is recommended
that you use NAT over IPSec (see
Virtual Address Mapping on page 338
) if
the local and remote IP addresses overlap.
If a VPN rule’s local and remote network settings are both set to 0.0.0.0
(any), no traffic goes through the VPN tunnel if you select
The Local
Network
.
Apply
Click
Apply
to save your changes back to the ZyWALL.
Reset
Click
Reset
to begin configuring this screen afresh.
Table 92
SECURITY > VPN > Global Setting (continued)
LABEL
DESCRIPTION