mlse
09-22-2006, 12:27 PM
Hi,
As far as I understand, port numbers are unsigned 2-byte entities with certain ranges being reserved for protocol purposes.
When a router performs network-address translation (and so aliases the local ports to remote values during the translation itself), are there any hard and fast rules as to the way that port numbers are mapped between different machines?
I have heard anecdotal evidence that the MSB and the following three bits of the upper byte of a translated (i.e. uplink side) port number are unique to a given local machine (for example if local machine A was mapped to router port numbers in the range 0xD000-0xDFFF then local machine B could not be mapped to any port numbers in this range).
If this was true it would be convenient for my purposes!
Any thoughts?
TIA,
Mike.
As far as I understand, port numbers are unsigned 2-byte entities with certain ranges being reserved for protocol purposes.
When a router performs network-address translation (and so aliases the local ports to remote values during the translation itself), are there any hard and fast rules as to the way that port numbers are mapped between different machines?
I have heard anecdotal evidence that the MSB and the following three bits of the upper byte of a translated (i.e. uplink side) port number are unique to a given local machine (for example if local machine A was mapped to router port numbers in the range 0xD000-0xDFFF then local machine B could not be mapped to any port numbers in this range).
If this was true it would be convenient for my purposes!
Any thoughts?
TIA,
Mike.