Appendix H - Using Dhcp Option 125 - Black Box iPATH ACR1000A-CTL-24 User Manual

APPENDIX H - USING DHCP OPTION 125

DHCP Option 125 is a vendor-specific feature that provides additional information to the Agility Remotes and Locals when
requesting an IP Address. The option gives the endpoints the IP Address of the Primary and any other Backup or Satellite iPATH
Servers that reside on the network.
The information is provided in a hex code which can be formatted slightly differently depending on the DHCP Server, but will
typically look like:-
0000621f0a01080a0014050a001406
The Hex code is broken down to the following elements:
0000621f Enterprise number (25119)
0a Length A
01 Sub-option 1
08 Length B
0a001405 10.0.20.5 (Primary iPATH)
0a001406 10.0.20.6 (Backup iPATH)
The Enterprise element of hex code is fixed and does not change, however the IP Address and lengths A & B hex values will
change depending on the Agility configuration.
The first IP address in the list must always be the Primary iPATH Server, followed by the Backup then Satellite iPATH's.
There are a number of online websites that help you convert an IP Address into a hex number. Alternatively, you could use a
Calculator with a Hex and Dec function which you may find is built into your computers operating system.
An IP Address hex code can be calculated by converting each of the four octet decimals individually into hex.
Decimal Hex
10 0a
0 00
20 14
5 05
10.0.20.5 = 0a001405
Each hex IP Address is 4-bytes in length:
0a 00 14
1 1 1
The Lengths A and B values will change depending on the number of IP Addresses that are included.
98
05
1 (Total 4 bytes)
1.877.877.2269 BLACKBOX.COM
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