3Com REMOTE ACCESS SYSTEM 1500, Management Manual

Page: 262 / 300

260 C
HAPTER
16: U
SING
N
ETWORK
A
DDRESS
T
RANSLATION AND
P
ORT
A
DDRESS
T
RANSLATION
To list active PAT port mappings, use the following command:
list pat user <username> port
Case Studies
This section contains one case study for NAT and one for PAT.
NAT Case Study A private network with a RAS 1500 requires access to a public network.
This access is across a PPP link with “ascend” compression initiated by the
RAS1 500.
The user ID (“main”) and password (“ras”) have been agreed to by the
ISP. In the NAT user profile, the transmit_authentication setting must
match the user ID (“main”), and the send_password setting must match
the password (“ras”).
The public subnet allocated by the ISP for use by this private network is
202.55.55.40/29.
The RAS 1500 is assigned the address 202.55.55.41/29.
The private network has two servers that will be accessed by hosts from
the public network. The ISP access number is 3067.
The local area network (LAN) configuration of the RAS 1500 is the same
as it would be without a NAT user added.
A NAT user is a normal user with some configuration differences. The
differences are the following:
■
IP address assignment for the wide area network (WAN) link
■
Routing behavior over the WAN link
■
Addition of static NAT mappings
■
Addition of a public IP pool for dynamic NAT mappings
Private networks should not be advertised to the public network, hence
the ip_routing parameter is set to “listen.”