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(BBN) X.25 DDN Dynamic Host Addressing

Is anyone familier with how hosts attached (via x.25) to the old BBN packet switches were able to obtain there addresses dynamicly ? They do it with the CALL REQUEST packet (utilizing an x.25 facility I believe). When they did this, it was the actual IP address of the packet switch port that they assumed as their own to communicate with other hosts.

I would like to find out if this can be done with the Cisco IOS (so I can replace a couple of old BBN packet switches) to support a couple of legacy hosts that do not allow for staticly assigning IP addresses. The software is proprietary so I am very limited as to what I can do with the host.


Re: (BBN) X.25 DDN Dynamic Host Addressing

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Thank you for posting.

Cisco Employee

I just noticed this question

I just noticed this question doing an unrelated search. Though my answer is 15 years late, I thought I'd add this note to the memory hole.

What you seem to have is DDN X.25. Cisco was a leader in this in the early 1990s. This was IP over X.25 with a static mapping of IP address to X.121 address. The method is described in and the command on the serial port is

encapsulation x25 ddn 

There is a lot of quirkiness to X.25 config. In the extemely unlikely event that this system is still running a decade and a half later, you have options!