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How to Configure Option 43 When Huawei APs Are Connected to DHCP Servers of Different Vendors

This document describes how to configure Option 43 when Huawei APs are connected to DHCP servers of different vendors.

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How to Configure Option 43 When Huawei APs Are Connected to DHCP Servers of Different Vendors

How to Configure Option 43 When Huawei APs Are Connected to DHCP Servers of Different Vendors

What Is Option 43 in DHCP?

DHCP Overview

The Dynamic Host Configuration Protocol (DHCP) dynamically configures and uniformly manages IP addresses of hosts. DHCP is defined in RFC 2131 and uses the client/server communication model. A DHCP client requests configuration information from a DHCP server, and the DHCP server returns the configuration information allocated to the DHCP client.

A DHCP server communicates with DHCP clients by exchanging DHCP messages. Figure 1-1 shows the DHCP message format. Digits in the parentheses indicate the field length, in octets.

Figure 1-1 DHCP message format

DHCP Option Field

A variable options field in a DHCP message is used to store control information and parameters allocated to the DHCP client. As shown in Figure 1-2, the options field consists of three parts: Type, Length, and Value. Table 1-1 describes the three parts.

Figure 1-2 Format of the options field

Table 1-1 Description of the options field

Field

Length

Description

Type

1 octet

Information type

Length

1 octet

Length of the information content

Value

Depending on the Length option

Information content

The value of the DHCP options field ranges from 1 to 255. DHCP options include predefined and user-defined options.

Option 43

Option 43 is a user-defined option, indicating vendor-specific information. A device that supports Option 43 is used to connect to different terminals such as IP phones and APs.

Figure 1-3 shows the format of Option 43.

Figure 1-3 Format of Option 43

DHCP servers and clients use Option 43 to exchange vendor-specific information. When a DHCP server receives a DHCP request message with parameter 43 encapsulated in Option 55, it encapsulates Option 43 in a reply message and sends the message to the DHCP client.

Option 43 supports suboptions, as shown in Figure 1-3.

  • Sub-option type: type of the suboption
  • Sub-option length: length of the suboption
  • Sub-option value: value of the suboption

Relationship Between Option 43 and Huawei APs

APs in Fit mode can go online without configurations, and a WAC will manage the APs and deliver configurations to them. To go online on the WAC, the APs need to obtain IP addresses to access the network and then discover the WAC to set up connections.

In most cases, APs obtain IP addresses through DHCP. An AP functions as a DHCP client and requests an IP address from a DHCP server on the network.

The WAC discovery process varies according to the networking mode.

  • Layer 2 network between the WAC and APs: APs can discover the WAC in broadcast mode.
  • Layer 3 network between the WAC and APs: APs cannot discover the WAC in broadcast mode. Instead, a DHCP server uses the Option 43 field to carry WAC information and sends the information to APs. After resolving the WAC's IP address, the APs set up connections with the WAC in unicast mode.

On a Layer 2 network, the DHCP Option 43 field can also be used to send WAC information to APs. This mode takes precedence over the broadcast mode.

Therefore, when APs are connected to a DHCP server, the Option 43 field is used to specify the WAC's IP address so that the APs can set up connections with the WAC. For details about the connection process between an AP and a WAC, see How an AP Joins an AC and Troubleshooting Any Join Failures.

Option 43 Formats Supported by Huawei APs

Identifying the Option 43 Format of a Single WAC

When a single WAC is specified for a Huawei AP, the AP can identify suboptions 1, 2, and 3 of Option 43. Assuming that the IP address of a WAC is 192.168.100.1 and a Huawei switch is used as a DHCP server, any of the following configurations can be used to configure the suboptions of Option 43:

  • Suboption 1 (Hexadecimal)
    dhcp server option 43 sub-option 1 hex c0a86401

    c0, a8, 64, and 01 are the hexadecimal (hex) numbers converted from 192, 168, 100, and 1 in the IP address, respectively.

    You can also configure suboptions in hex, which is equivalent to the preceding configuration. The two configurations can overwrite each other.

    dhcp server option 43 hex 0104c0a86401

    01: suboption type 1.

    04: suboption length, indicating the number of octets in an IP address. Each IP address occupies 4 octets. Therefore, the suboption length is the number of IP addresses times 4 in hex.

    c0 a8 64 01: IP address 192 168 100 1 in hex.

  • Suboption 2 (Decimal)
    dhcp server option 43 sub-option 2 ip-address 192.168.100.1

    You can also configure suboptions in hex, which is equivalent to the preceding configuration. The two configurations can overwrite each other.

    dhcp server option 43 hex 0204c0a86401

    02: suboption type 2.

    04: suboption length, indicating the number of octets in an IP address. Each IP address occupies 4 octets. Therefore, the suboption length is the number of IP addresses times 4 in hex.

    c0 a8 64 01: IP address 192 168 100 1 in hex.

  • Suboption 3 (ASCII Code)
    dhcp server option 43 sub-option 3 ascii 192.168.100.1

    You can also configure suboptions in hex, which is equivalent to the preceding configuration. The two configurations can overwrite each other.

    dhcp server option 43 hex 030d3139322e3136382e3130302e31

    03: suboption type 3.

    0d: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character string 192.168.100.1.

    31 39 32 2e 31 36 38 2e 31 30 30 2e 31: ASCII code of the character string 192.168.100.1. Numbers 0 to 9 correspond to 30 to 39 in ASCII format, and the period (.) corresponds to 2e.

Identifying the Option 43 Format of Multiple WACs

When multiple WACs are specified for a Huawei AP, the AP can identify suboptions 2 and 3 of Option 43. Assuming that the IP addresses of two WACs are 192.168.100.1 and 192.168.100.2, any of the following configurations can be used to configure the suboptions of Option 43: The AP sends connection requests to all WACs according to the sequence in which their IP addresses are specified. An AP supports a maximum of eight WAC IP addresses.
  • Suboption 2 (Decimal)
    dhcp server option 43 sub-option 2 ip-address 192.168.100.1 192.168.100.2

    You can also configure suboptions in hex, which is equivalent to the preceding configuration. The two configurations can overwrite each other.

    dhcp server option 43 hex 0208c0a86401c0a86402

    02: suboption type 2.

    08: suboption length, indicating the number of octets in an IP address. Each IP address occupies 4 octets. Therefore, the suboption length is the number of IP addresses times 4 in hex.

    c0 a8 64 01: IP address 192 168 100 1 in hex.

    c0 a8 64 02: IP address 192 168 100 2 in hex.

  • Suboption 3 (ASCII Code)
    dhcp server option 43 sub-option 3 ascii 192.168.100.1,192.168.100.2

    The IP addresses are separated by commas (,) without spaces.

    You can also configure suboptions in hex, which is equivalent to the preceding configuration. The two configurations can overwrite each other.

    dhcp server option 43 hex 031b3139322e3136382e3130302e312c3139322e3136382e3130302e32

    03: suboption type 3.

    1b: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character strings 192.168.100.1 and 192.168.100.2.

    31 39 32 2e 31 36 38 2e 31 30 30 2e 31: ASCII code of the character string 192.168.100.1.

    2c: ASCII code for the comma (,) as a character string.

    31 39 32 2e 31 36 38 2e 31 30 30 2e 32: ASCII code of the character string 192.168.100.2.

    Numbers 0 to 9 correspond to 30 to 39 in ASCII format, the period (.) corresponds to 2e, and the comma (,) corresponds to 2c.

Option 43 Formats Supported by DHCP Servers of Different Vendors

APs can identify three types of Option 43 formats, but Option 43 formats that can be identified by DHCP servers vary according to vendors.

The following table lists Option 43 formats that can be identified by DHCP servers of only some vendors. For details about the supported DHCP server models and configuration methods, see the corresponding product documents.

Table 1-2 Option 43 formats supported by DHCP servers of different vendors

Vendor

Suboption 1 (Hex)

Suboption 2 (Decimal)

Suboption 3 (ASCII Code)

Huawei

Supported1

Supported

Supported2

Cisco

Not supported

Not supported

Supported

Juniper

Not supported

Not supported

Supported

Linux ISC

Not supported

Supported

Not supported

Windows

Not supported

Not supported

Supported

Infoblox

Not supported

Not supported

Supported

1. This suboption supports the configuration of only a single WAC but not multiple WACs.

2. During the configuration, you can directly enter a character string without converting the character string into ASCII code, which is simpler.

Configuring Option 43 on a Huawei DHCP Server

Supported Formats

Suboptions 1, 2, and 3

Configuration Method

This example uses a Huawei WAC with the IP address of 192.168.100.1 as the DHCP server to describe how to configure Option 43.

You can use any of the following configurations:

dhcp server option 43 sub-option 1 hex c0a86401
dhcp server option 43 sub-option 2 ip-address 192.168.100.1
dhcp server option 43 sub-option 3 ascii 192.168.100.1

Related Information

https://support.huawei.com/hedex/hdx.do?docid=EDOC1100192518&id=EN-US_CONCEPT_0176917721&lang=en

Configuring Option 43 on a Cisco DHCP Server

Supported Formats

Suboption 3

Configuration Method

This example uses a Cisco switch as the DHCP server to describe how to configure Option 43 to carry the WAC's IP address of 192.168.100.1.
#
ip dhcp pool test
 network 192.168.100.1 255.255.255.0
 default-router 192.168.100.1
 option 43 hex 030d3139322e3136382e3130302e31 
#

03: suboption type 3.

0d: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character string 192.168.100.1.

31 39 32 2e 31 36 38 2e 31 30 30 2e 31: ASCII code of the character string 192.168.100.1.

Numbers 0 to 9 correspond to 30 to 39 in ASCII format, and the period (.) corresponds to 2e.

Related Information

http://www.cisco.com/c/en/us/td/docs/wireless/access_point/1550/installation/guide/1550hig/1550_axf.html

Configuring Option 43 on a Juniper DHCP Server

Supported Formats

Suboption 3

Configuration Method

This example uses a Juniper switch as the DHCP server to describe how to configure Option 43 to carry the WAC's IP address of 192.168.100.1.

#
set system services dhcp option 43 byte-stream "0x03 0x0D 0x31 0x39 0x32 0x2E 0x31 0x36 0x38 0x2E 0x31 0x30 0x30 0x2E 0x31" 
#

0x03: suboption type 3.

0x0D: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character string 192.168.100.1.

0x31 0x39 0x32 0x2E 0x31 0x36 0x38 0x2E 0x31 0x30 0x30 0x2E 0x31: ASCII code of the character string 192.168.100.1.

Numbers 0 to 9 correspond to 30 to 39 in ASCII format, and the period (.) corresponds to 2E.

Related Information

http://kb.juniper.net/InfoCenter/index?page=content&id=KB23834&actp=search

http://kb.juniper.net/InfoCenter/index?page=content&id=KB4243&actp=search

http://kb.juniper.net/InfoCenter/index?page=content&id=KB24005&actp=search

Configuring Option 43 on a Linux ISC DHCP Server

Supported Formats

Suboption 2

Configuration Method

The following uses a Linux ISC DHCP server as an example to describe how to configure Option 43.
  • Configuration file path

    /etc/dhcp/dhcpd.conf

  • Configuration file example

    The DHCP server obtains vendor information based on the Option 60 field carried in the packet received from the client, specifies the WAC address for the client based on the vendor information, and sends the WAC address to the client through Option 43. For example, specify the WAC address of 192.168.247.5 for Cisco APs and 192.168.247.55 for Huawei APs.

    #
ddns-update-style interim;
option space Cisco_LWAPP_AP;
 option Cisco_LWAPP_AP.server-address code 241 = array of ip-address;
 option space Huawei-AP6050DN;
 option Huawei-AP6050DN.server-address code 1 = array of ip-address;

 subnet 192.3.1.0 netmask 255.255.255.0 {
 authoritative;
 range 192.3.1.100 192.3.1.254;
 option subnet-mask 255.255.255.0;
 option broadcast-address 192.3.1.255;
 option routers 192.3.1.1;
 option domain-name "huawei.com";
 option domain-name-servers 192.168.247.2, 192.168.247.3;
 default-lease-time 300;

 class "Cisco-AP-c1700" {
 match if option vendor-class-identifier = "Cisco-AP-c1700";
 option vendor-class-identifier "Cisco-AP-c1700";
 vendor-option-space Cisco_LWAPP_AP;
 option Cisco_LWAPP_AP.server-address 192.168.247.5; }

 class "huawei AP" {
 match if option vendor-class-identifier = "huawei AP";
 option vendor-class-identifier "huawei AP";
 vendor-option-space Huawei-AP6050DN;
 option Huawei-AP6050DN.server-address 192.168.247.55; }

 subnet 192.168.1.0 netmask 255.255.255.0 {
 }
#

Related Information

None

Configuring Option 43 on a Windows DHCP Server

Supported Formats

Suboption 3

Configuration Method

This example uses a Windows DHCP server as an example to describe how to configure Option 43 to carry the WAC's IP address 192.168.22.1.
  • Enter the window for configuring the Window DHCP server, as shown in Figure 1-4.
    Figure 1-4 Window DHCP server configuration
  • Enter a hex number under Binary, as shown in Figure 1-5.
    Figure 1-5 Option 43 configuration

    03: suboption type 3.

    0C: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character string 192.168.22.1.

    31 39 32 2E 31 36 38 2E 32 32 2E 31: ASCII code of the character string 192.168.22.1.

    Numbers 0 to 9 correspond to 30 to 39 in ASCII format, and the period (.) corresponds to 2E.

    You do not need to enter ASCII. After digits are entered in Binary, ASCII is automatically filled.

Related Information

None

Configuring Option 43 on an Infoblox DHCP Server

Supported Formats

Suboption 3

Configuration Method

This example uses an Infoblox server as the DHCP server to describe how to configure Option 43 to carry the WAC's IP address of 10.6.2.1.

On the Infoblox server, enter the IP address 10.6.2.1 in the format of 03:08:31:30:2e:36:2e:32:2e:31. Separate every two characters with a semicolon (:), as shown in Figure 1-6.

Figure 1-6 Configuring Option 43 on the Infoblox server

03: suboption type 3.

08: suboption length. The IP address and symbols are expressed as characters. Therefore, the suboption length is the hex string converted from the number of characters in the character string 10.6.2.1.

31:30:2e:36:2e:32:2e:31: ASCII code of the character string 10.6.2.1, separated by semicolons (:).

Numbers 0 to 9 correspond to 30 to 39 in ASCII format, and the period (.) corresponds to 2e.

Related Information

None

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Updated: 2022-07-01

Document ID: EDOC1100202779

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