Black Box iPATH ACR1000A-CTL-24 User Manual page 99

The Length B value is the total byte count of the hex IP Addresses. In the example below, there are 2x IP hex addresses. Each IP
hex address is 4-bytes, therefore Length B is 8-bytes in total which equates to 08 in hex.
Length B
0000621f0a01080a0014050a001406
Length A includes Sub-option 1 (1-byte) and the Length B value (1-byte) plus the total of Length B (8-bytes). This makes the total
10-bytes which equates to 0a in hex.
Length A
0000621f0a01080a0014050a001406
2 bytes
Example
In the following example an additional IP address will be added to the existing DHCP option 125 hex code shown previously. It
will be a Satellite iPATH whose IP address is 10.0.30.1 which is on a different subnet.
Step 1: Convert IP Address 10.0.30.1 into hex, which is 0a001e01. Add it to the end of the hex code:
0000621f..01..0a0014050a0014060a001e01
Step 2: Calculate Length B. Since we now have 3x IP addresses and each hex address is 4-bytes, the total length is 12-bytes
which equates to 0c in hex:
0000621f..010c0a0014050a0014060a001e01
Step 3: Calculate Length A. This is the total of Length B plus the byte count for Sub-option 1 and the Length B value. The Sub-
option 1 and Length B values are 1-byte each, the Length B total is 12-bytes. This makes the total of Length A to be 14-bytes
which equates to 0e in hex:
0000621f0e010c0a0014050a0014060a001e01
4 bytes 4 bytes (Total 8 bytes)
4 bytes 4 bytes (Total 10 bytes)
1.877.877.2269 BLACKBOX.COM
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