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by FujiApple
548 days ago
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You can, with several caveats, detect which hop(s) on the path perform NAT by using some trickery [1]: > NAT devices are detected by observing a difference in the expected and actual checksum of the UDP packet that is returned as the part of the Original Datagram in the ICMP Time Exceeded message. If they differ then it indicates that a NAT device has modified the packet. This happens because the NAT device must recalculate the UDP checksum after modifying the packet (i.e. translating the source port) and so the checksum in the UDP packet that is nested in the ICMP error may not, depending on the device, match the original checksum. [1] https://github.com/fujiapple852/trippy/releases/tag/0.11.0 |
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