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The router performs the following process in overloading inside global addresses, as shown in Figure 2. Both host B and host C believe they are communicating with a single host at address 2.2.2.2. They are actually communicating with different hosts; the port number is the differentiator. In fact, many inside hosts could share the inside global IP address by using many port numbers.
1. The user at host 1.1.1.1 opens a connection to host B.
2. The first packet that the router receives from host 1.1.1.1 causes the router to check its NAT table:
–If no translation entry exists, the router determines that address 1.1.1.1 must be translated, and sets up a translation of inside local address 1.1.1.1 to a legal global address.
–If overloading is enabled, and another translation is active, the router reuses the global address from that translation and saves enough information to be able to translate back. This type of entry is called an extended entry.
3. The router replaces the inside local source address 1.1.1.1 with the selected global address and forwards the packet.
4. Host B receives the packet and responds to host 1.1.1.1 by using the inside global IP address 2.2.2.2.
5. When the router receives the packet with the inside global IP address, it performs a NAT table lookup, using the protocol, the inside global address and port, and the outside address and port as a key; translates the address to inside local address 1.1.1.1; and forwards the packet to host 1.1.1.1.
Host 1.1.1.1 receives the packet and continues the conversation. The router performs Steps 2 through 5 for each packet.
SUMMARY STEPS
1. enable
2. configure terminal
3. ip nat pool CLIENTS start-ip end-ip {netmask netmask| prefix-length prefix-length}
4. access-list access-list-number permit source [source-wildcard]
5. ip nat inside source list access-list-number pool name overload
6. interface type number
7. ip address ip-address mask
8. ip nat inside
9. exit
10. interface type number
11. ip address ip-address mask
12. ip nat outside
Bei Fragen nur schreiben, is vo der Cisco Seite über NAT.
mfg
onedread
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Cisco C3845 soll für 1:1 NAT eingerichtet werden
