Draytek 2800 Series User Guide

Page of 197
 
Vigor2800 Series User’s Guide 
77
two IP addresses of 192.168.1.200 and 192.168.1.201 are 
reserved for ISDN remote dial-in user. 
3
3
.
.
7
7
.
.
3
3
 
 
I
I
P
P
S
S
e
e
c
c
 
 
G
G
e
e
n
n
e
e
r
r
a
a
l
l
 
 
S
S
e
e
t
t
u
u
p
p
 
 
In IPSec General Setup, there are two major parts of configuration.   
There are two phases of IPSec.   
¾ 
Phase 1: negotiation of IKE parameters including encryption, hash, Diffie-Hellman 
parameter values, and lifetime to protect the following IKE exchange, authentication of 
both peers using either a Pre-Shared Key or Digital Signature (x.509). The peer that 
starts the negotiation proposes all its policies to the remote peer and then remote peer 
tries to find a highest-priority match with its policies. Eventually to set up a secure 
tunnel for IKE Phase 2. 
¾ 
Phase 2: negotiation IPSec security methods including Authentication Header (AH) or 
Encapsulating Security Payload (ESP) for the following IKE exchange and mutual 
examination of the secure tunnel establishment. 
There are two encapsulation methods used in IPSec, Transport and Tunnel. The Transport 
mode will add the AH/ESP payload and use original IP header to encapsulate the data 
payload only. It can just apply to local packet, e.g., L2TP over IPSec. The Tunnel mode will 
not only add the AH/ESP payload but also use a new IP header (Tunneled IP header) to 
encapsulate the whole original IP packet. 
Authentication Header (AH) provides data authentication and integrity for IP packets passed 
between VPN peers. This is achieved by a keyed one-way hash function to the packet to 
create a message digest. This digest will be put in the AH and transmitted along with packets. 
On the receiving side, the peer will perform the same one-way hash on the packet and 
compare the value with the one in the AH it receives. 
Encapsulating Security Payload (ESP) is a security protocol that provides data 
confidentiality and protection with optional authentication and replay detection service.   
 
IKE Authentication Method   This usually applies to those are remote dial-in user or node 
(LAN-to-LAN) which uses dynamic IP address and 
IPSec-related VPN connections such as L2TP over IPSec 
and IPSec tunnel.   
Pre-Shared Key -Currently only support Pre-Shared Key 
authentication. 
Pre-Shared Key- Specify a key for IKE authentication 
Re-type Pre-Shared Key-Confirm the pre-shared key.