User Guide

Chapter 4. Configuring Special Features 81
5. When using NAT with a remote router, either the remote ISP
must
supply the IP address for NAT translation
or the user
must
configure the IP address for NAT translation locally.
6. Any number of PCs on the LAN may have a connection to the same or different remote routers at the same
time. In reality, the number of PCs on the LAN that can be supported is limited by the amount of memory
consumed by the router to maintain table information
and
by the number of connections the router “thinks”
are currently active. Theoretically, up to 64,000 active connections per protocol type—TCP/UDP—can be
concurrently running, if the table space is available.
Masquerading
With masquerading, multiple local (PC) IP addresses are mapped to a single global IP address. Many local (PCs)
IP addresses are therefore hidden behind a single global IP address. The advantage of this type of NAT is that
users only need one global IP address, but the entire local LAN can still access the Internet. This NAT technique
requires not only remapping IP addresses but also TCP and UDP ports.
Each PC on the LAN side has an IP address and a mask. When the router connects to an ISP, the router appears to
be a “host” with one IP address and mask. The IP address that the router uses to communicate with the ISP is
obtained dynamically (with PPP/IPCP or DHCP) or is statically configured. When the PC connects to the ISP, the
IP address and port used by the PC are remapped to the IP address assigned to the router. This remapping is done
dynamically.
Client Configuration
!
!!
!
Enable NAT
To enable NAT, use the commands:
remote setIpTranslate on <
remoteName
>
save
The
save
command makes the above changes persistent across boots; these changes turn NAT on when
you are connected to this remote router.
!
!!
!
Obtain an IP Address for NAT
The IP address (the IP address “known” by the remote ISP) used for this type of NAT can be assigned in
two ways.
The ISP dynamically assigns the IP address. Use the commands:
remote setSrcIpAddr
0.0.0.0 0.0.0.0 <
remoteName
>
save
The IP address is assigned locally. Use the commands:
remote setSrcIpAddr
ww.xx.yy.zz
255.255.255.255 <
remoteName
>
save
Note:
ww.xx.yy.zz
is the IP address that the user on the local LAN assigns.