256 CHAPTER 16: USING NETWORK ADDRESS T RANSLATION AND PORT A DDRESS T RANSLATIONPAT is either “dynamic” or “static.” The preceding example is dynamicand is depicted in the following diagram. (Figure 21 shows feweraddresses in the pool than in the preceding example.)Figure 21 Dynamic PATFigure 22 depicts static PAT.Figure 22 Static PATPublic192.168.111.1, 4444Private200.1.1.1, 5001200.1.1.1, 5003200.1.1.1, 5002When no users are attempting toaccess the public network, noaddresses or ports are assigned.When a user attempts to access the publicnetwork, the private address and port of theuser are assigned the first available IP addressand port in the public IP address pool.When another user attempts to access thepublic network, the private address and port ofthe user are assigned the next available IPaddress and port in the public IP address pool.When a connection ends,the public IP address andport of that connectionagain become available.Public192.168.111.1, 4444Private200.1.1.1, 5001200.1.1.1, 5003200.1.1.1, 5002192.168.111.3, 4444PublicPrivate200.1.1.1, 5001200.1.1.1, 5003200.1.1.1, 5002192.168.111.3, 4444PublicPrivate200.1.1.1, 5001200.1.1.1, 5003200.1.1.1, 5002P u b l i c1 9 2 . 1 6 8 . 1 1 1 . 1 , 4 4 4 4P r i v a t e2 0 0 . 1 . 1 . 1 , 5 0 0 11 9 2 . 1 6 8 . 1 1 1 . 4 , 4 4 4 41 9 2 . 1 6 8 . 1 1 1 . 3 , 4 4 4 41 9 2 . 1 6 8 . 1 1 1 . 2 , 4 4 4 42 0 0 . 1 . 1 . 1 , 5 0 0 42 0 0 . 1 . 1 . 1 , 5 0 0 32 0 0 . 1 . 1 . 1 , 5 0 0 2W h e n a u s e r a t t e m p t s t o a c c e s s t h e p u b l i cnetwork, the private address and port ofthe user are assigned the public IPaddress and port defined in the table.
