Exam 350-401 topic 1 question 449 discussion

D is correct

The answer is D What is Option 43 hex? This hex value is used in something called DHCP Option 43 by the Cisco APs to discover a WLC if they haven't already found one through other means such as Layer 2/3 broadcasts, local WLC lists in their NVRAM and even a DNS discovery

The Answer is D This Article straight from Cisco White Papers mentions it again and again and again, just do a CTRL F and search the word Hex and you will see all the mentions of Hex, it doesn't say it is required but it doesn't have to, just by simply reading the article you can make that conclusion that it is.

When DHCP servers are programmed to offer WLAN Controller IP addresses as Option 43 for Cisco Aironet LAPs, the sub-option TLV block is defined in this way: Type - 0xf1 (decimal 241). Length - Number of controller IP addresses * 4. Value - List of the WLC management interfaces, typically translated to hexadecimal values. The semantics of DHCP server configuration vary based on the DHCP server vendor. This document contains specific instructions on the Microsoft DHCP server, Cisco IOS DHCP server, Linux ISC DHCP Server, Cisco Network Registrar DHCP server, and Lucent QIP DHCP Server. For other DHCP server products, consult the vendor documentation for instructions on vendor specific options. (Source: https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/97066-dhcp-option-43-00.html)

the answer is C ASCII (American Standard Code for Information Interchange) is the most common character encoding format for text data in computers and on the internet. In standard ASCII-encoded data, there are unique values for 128 alphabetic, numeric or special additional characters and control codes. Hex is not a character formatting is a number system.

Add the Option 43 line with this syntax: option 43 hex <hexadecimal string> The hexadecimal string in step 3 is assembled as a sequence of the TLV values for the Option 43 suboption: Type + Length + Value. Type is always the suboption code 0xf1. Length is the number of controller management IP addresses times 4 in hex. Value is the IP address of the controller listed sequentially in hex. For example, suppose there are two controllers with management interface IP addresses, 192.168.10.5 and 192.168.10.20. The type is 0xf1. The length is 2 * 4 = 8 = 0x08. The IP addresses translate to c0a80a05 (192.168.10.5) and c0a80a14 (192.168.10.20). When the string is assembled, it yields f108c0a80a05c0a80a14. The Cisco IOS command that is added to the DHCP scope is: option 43 hex f108c0a80a05c0a80a14

100% D

Agreed with Dougj here, When DHCP servers are programmed to offer WLAN Controller IP addresses as Option 43 for Cisco 1000 Series APs the sub-option TLV block is defined in this way: Type - 0x66 (decimal 102). Length: - A count of the characters of the ASCII string in the Value field. Length must include the commas if there is more than one controller specified, but not a zero-terminator. Value: - A non-zero terminated ASCII string that is a comma-separated list of controllers. No spaces must be embedded in the list. When DHCP servers are programmed to offer WLAN Controller IP addresses as Option 43 for other Cisco Aironet LAPs, the sub-option TLV block is defined in this way: Type - 0xf1 (decimal 241). Length - Number of controller IP addresses * 4. Value - List of the WLC management interfaces, typically translated to hexadecimal values.

ASCII was only used for the old Cisco 1000 series access points

Answer: D

https://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/97066-dhcp-option-43-00.html

Answer C applies when using Cisco DNAC / fabric, option 43 would also point to the DNAC VIP IP, Answer D is correct.

Why not C ?

It is HEX.