User's Manual

397
Users Manual of CS-6306R
available, the software cannot distribute an address and NAT will drop the message and returns an ICMP
message indicating the host cannot be reached.
The switch with NAT configured should not publish the local network. However, the routing information that
NAT receives from the outside can be published in the single-connection domain.
43.2.1.3 NAT Terms
As said above, the term “inside” means those networks which are possessed by organizations and have to be
transformed. In this domain, the host has an address in one address space. At the outside, the host will
possess an address in another address space when the NAT is configured. The first address space means
the local address space, while the second address space means the global address space.
Similarly, the term “outside” means the network that the single network connects, generally out of control of an
organization. The addresses of the hosts in the outside network need to translate a certain address and may
be classified into two types of addresses: local address and global address.
NAT uses the following definitions:
 Inside local address: IP address that is allocated to a host in the inside network. The address may not
be the legal IP address distributed by Network Information Center (NIC) or service provider (SP).
 Inside global address: legal IP address distributed by NIC or SP, describing one or multiple IP
addresses for the outside network.
 Outside local address: IP address of the outside host that appears in the inside network. It may be
illegal. It can be distributed through the routable address space in the inside network.
 Outside global address: IP address that the owner of the host distributes to the host in the outside
network, which can be distributed from the global address space or the network space.
43.2.1.4 NAT Regulation Matching Order
When NAT translates message, the configured NAT regulations must first be matched. There are three
classes of NAT regulations: inside source address mapping, outside source address mapping and inside
destination address mapping. Each class has its own subclasses. The following case takes the inside source
address mapping as an example to introduce the subclass order of the NAT matching regulations:
 Static TCP/UDP port mapping regulation
 Static single address mapping regulations
 Static network segment mapping regulations
 Dynamic POOL address mapping regulations
 PAT mapping regulations
The regulations in the same subclass in the same class and the three classes are matched according the
sequence they are being added. When you run the show running command, the order to display the NAT
regulations is the same as the actual matching order.
43.2.2 NAT Configuration Task List
Before configuring any NAT, you must know the range of the inside local address and inside global address.
The NAT configuration task list is shown as follows: