cisco ccna 4 chapter 8 exam answers

cisco ccna 4 chapter 8 exam answers.PAT ExampleTake a look at an example of PAT usage, as shown in Figure 22.2. In this example, both PCs Telnet to 199.199.199.1, and both connections use a source port number of 50000 o When these connections reach the address translation device, the address translation device performs a PAT o For the first connection (assuming it was initiated by PC-A), the source IP address (internal local IP address) is changed to 200.200. 200.7 (the internal global IP address). Since this is the first connection and its source port number is not found in the translation table, retain that source port number. When PC-B establishes a Telnet connection to the remote device, it uses a source port number (50000) that is already in the translation table-used by another connection to the Telnet server, so the address translation device changes the source port number 50000 to a port number not found in the translation table, such as 50001 o In this way, when the Telnet server sends traffic to the internal When the Telnet server sends traffic to the internal PC, the address translation device can distinguish between the two connections based on the destination IP address and port number in the reply packet and convert them correctly: for the reply packet with a destination port number of 50000, redirect it to PC-A; for the reply packet with a destination port number of 50001, change the destination port number to 50000 and redirect it to PC-BO address translation The device also converts the destination IP address to the internal local address of the device to which the packet is to be forwarded.Conversion TableInternal Local IP Address Internal Global IP Address Internal Local Port Number Internal Global Port Number 192.168.1.10 200.200.200.7 50,000 50,000 192.168.1.11 200.200.200.7 50,000 50,001Internal network E0 InternetPC-A 192.168.1.10PC-B 192.168.1.11Telnet server 199.199.199.1Figure 22.2 PAT ExampleThe port numbers in TCP and UDP headers are 16 bits long, so theoretically 65536 internal connections can be represented using a single public IP address, but in practice 4000-16000, since many port numbers are reserved or private. Note that it is not necessary to stick to one address translation; for example, for internal-to-external connections, PAT can be used, while for external-to-internal connections, NAT(>) can be used.