题目

INTRO TO COMPUTER NETWORKS (CS_372_400_U2025) Module 5 & 6 Summary Exercises

多重下拉选择题

A private network uses a NAPT device at public IP address 197.196.100.80 The computers in the network use addresses of the form 10.0.0.x/22. Suppose that computer inside the NATed network sends a request with Source address: 10.0.1.10 Source port: 530 Destination address: 60.25.40.10 Destination port: 20 The next available port number on the NAPT device is 10123. PART 1: What source and destination information do the request packet headers contain when the request is sent out by the sending host? Source address: [ Select ] 10123 60.25.40.10 530 197.196.100.80 10.0.1.10 20 Source port : [ Select ] 10123 10.0.1.10 530 60.25.40.10 197.196.100.80 20 Destination address: 60.25.40.10 Destination port : [ Select ] 10.0.1.10 530 20 197.196.100.80 10123 60.25.40.10 PART 2: What source and destination information do the request packet headers contain when the request is sent out by the NAT box? Source address: [ Select ] 60.25.40.10 20 10.0.1.10 197.196.100.80 530 10123 Source port : [ Select ] 60.25.40.10 10123 10.0.1.10 197.196.100.80 20 530 Destination address: [ Select ] 197.196.100.80 530 60.25.40.10 10.0.1.10 10123 20 Destination port : [ Select ] 10.0.1.10 60.25.40.10 10123 20 530 197.196.100.80 PART 3: What source and destination information do the response packet headers contain when the response is received by the NAT box? Source address: [ Select ] 60.25.40.10 10.0.1.10 10123 197.196.100.80 20 530 Source port : [ Select ] 60.25.40.10 20 10123 530 10.0.1.10 197.196.100.80 Destination address: [ Select ] 60.25.40.10 197.196.100.80 530 20 10.0.1.10 10123 Destination port : [ Select ] 530 60.25.40.10 10123 20 10.0.1.10 197.196.100.80 PART 4: What source and destination information do the response packet headers contain when the response is received by the original sending host? Source address: [ Select ] 197.196.100.80 20 10.0.1.10 530 60.25.40.10 10123 Source port : [ Select ] 530 60.25.40.10 20 10123 197.196.100.80 10.0.1.10 Destination address: [ Select ] 197.196.100.80 60.25.40.10 10123 530 20 10.0.1.10 Destination port : 530

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思路分析

This question is about how a PAT/NAT device translates and forwards a packet from an internal host to an external destination, and how headers look at different stages. I will walk through each Part and analyze the involved header fields step by step. Part 1: What does the sending host's request headers look like when the host inside the NATed network sends the packet out? - Before translation, the inside host has source address 10.0.1.10 and source port 530, destination 60.25.40.10 port 20. The NAT device assigns the next available port 10123 to represent this flow on the public side. Therefore, the outer header (the one sent to the Internet) will show source IP 197.196.100.80 (the NAT’s public address) and source port 10123, with the destination IP 6......Login to view full explanation