ZyXEL Communications Corporation VSG1435B101 Manual De Usuario

Chapter 21 IPSec

VSG1435-B101 Series User’s Guide

Finally, NAT is compatible with ESP in tunnel mode because integrity checks are 
performed over the combination of the "original header plus original payload," 
which is unchanged by a NAT device. The compatibility of AH and ESP with NAT in 
tunnel and transport modes is summarized in the following table.

Y* - This is supported in the ZyXEL Device if you enable NAT traversal.

With aggressive negotiation mode (see 

), the ZyXEL 

Device identifies incoming SAs by ID type and content since this identifying 
information is not encrypted. This enables the ZyXEL Device to distinguish 
between multiple rules for SAs that connect from remote IPSec routers that have 
dynamic WAN IP addresses.

Regardless of the ID type and content configuration, the ZyXEL Device does not 
allow you to save multiple active rules with overlapping local and remote IP 
addresses.

With main mode (see 

), the ID type and content are 

encrypted to provide identity protection. In this case the ZyXEL Device can only 
distinguish between up to 12 different incoming SAs that connect from remote 
IPSec routers that have dynamic WAN IP addresses. The ZyXEL Device can 
distinguish up to 48 incoming SAs because you can select between three 
encryption algorithms (DES, 3DES and AES), two authentication algorithms (MD5 
and SHA1) and eight key groups when you configure a VPN rule (see 

). The ID type and content act as an extra level of identification for 

incoming SAs.

The type of ID can be a domain name, an IP address or an e-mail address. The 
content is the IP address, domain name, or e-mail address. 

Table 90   VPN and NAT

AH

Transport

N

AH

Tunnel

N

ESP

Transport

Y*

ESP

Tunnel

Y

Table 91   Local ID Type and Content Fields

IP

Type the IP address of your computer.

DNS

Type a domain name (up to 31 characters) by which to identify this 
ZyXEL Device.