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DHCP Option 43 Vendor-Specific |
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Configuration Examples |
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Copyright © 2023 New H3C Technologies Co., Ltd. All rights reserved.
No part of this manual may be reproduced or transmitted in any form or by any means without prior written consent of New H3C Technologies Co., Ltd.
Except for the trademarks of New H3C Technologies Co., Ltd., any trademarks that may be mentioned in this document are the property of their respective owners.
The information in this document is subject to change without notice.
Contents
Option 43 sub-options supported by H3C APs
About PXE server address sub-option
About ACS parameter sub-option
Option 43 sub-options supported by different vendors
Option 43 configuration example for H3C DHCP servers
Option 43 configuration example for Huawei DHCP servers
Option 43 configuration example for Ruijie DHCP servers
Option 43 configuration example for Cisco DHCP servers
Option 43 configuration example for Ruckus DHCP servers
Option 43 configuration example for Extreme DHCP servers
Introduction
About DHCP options
The Dynamic Host Configuration Protocol (DHCP) adopts the client-server model to assign configuration information to network devices. Figure 1 shows the DHCP message format. The options field carries DHCP options. This field is variable in length and contains multiple optional parameters, including message type, lease duration, and domain name server IP address. DHCP uses the options field to carry information for dynamic address allocation and provide additional network configuration information for clients.
Figure 2 shows the DHCP option format. RFC 2132 offers standard definitions for many DHCP options, such as Option 3 and Option 6:
· Option 3—Router option. It specifies the gateway address to be assigned to the clients.
· Option 6—DNS server option. It specifies the DNS server IP address to be assigned to the clients.
Some options (such as Option 43) have no standard definitions in RFC 2132.
About Option 43
Option 43 is a vendor-specific option. If a DHCP client requests Option 43 information, the DHCP server will return a reply that carries Option 43. This option contains vendor-specific configuration information. In the fit AP+AC network architecture, an AP can use Option 43 to obtain the IP address of the AC, so the AP can associate with the AC.
As shown in Figure 3, the AP and the AC needs to establish a Layer 3 connection. However, the AP cannot obtain the IP address of the AC through broadcast, because they are in different VLANs. In this situation, the AP can request Option 43 information from the DHCP server. The DHCP server then returns a reply that contains the IP address of the AC in Option 43.
Figure 3 AP registration at Layer 3
As shown in Figure 4, the AP and the AC needs to establish a Layer 2 connection. Both the AP and the AC are in VLAN 100. The AP can obtain the IP address of the AC through broadcast or Option 43. The Option 43 method takes precedence over the broadcast method.
Figure 4 AP registration at Layer
Option 43 sub-options supported by H3C APs
The DHCP server supports configuring multiple Option 43 sub-options, including ACS parameter sub-option, service provider identifier sub-option, and PXE server address sub-option. Each sub-option supports both hexadecimal format and ASCII format. Figure 5 shows the format of Option 43.
H3C APs can recognize the PXE server address sub-option and the ACS parameter sub-option, but only when these sub-options are in hexadecimal format. The PXE server address sub-option and the ACS parameter sub-option are case-insensitive and have the same effect.
PXE server address sub-option
About PXE server address sub-option
This sub-option provides a DHCP client with PXE server address information, so the client can obtain the boot file or other control information from the PXE server.
Table 1 shows the fields of PXE server address sub-option.
Table 1 Fields of PXE server address sub-option
|
Field |
Length |
Remarks |
|
1 |
The value is fixed at 80, which represents PXE server address sub-option. |
|
|
1 |
This value specifies the length of the sub-option except for the Sub-option type field and the Sub-option length field, in bytes. |
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Sub-option value |
Variable length, which depends on the sub-option length. |
This value is in 0000 + Quantity of IPv4 AC addresses + Hexadecimal IPv4 AC addresses format. You can configure up to 16 IPv4 addresses in a row. Do not use any space to separate them. For example, 0000010a17c801 and 0000020a17c8010a17c802. |
Configuration examples
· To configure a PXE server address sub-option that contains IPv4 AC address 10.23.200.1, use the following settings:
¡ Sub-option type: 80.
¡ Sub-option length: 07. The length of 0000010a17c801 is 7 bytes.
¡ Sub-option value: 0000010a17c801. 0000 is a fixed part, 01 is the number of IPv4 AC addresses, 0a17c801 is AC address 10.23.200.1 in hexadecimal format.
When you configure the PXE server address sub-option in the DHCP address pool view of the DHCP server, the configuration is option 43 hex 80070000010a17c801.
· To configure a PXE server address sub-option that contains IPv4 AC addresses 10.23.200.1 and 10.23.200.2, use the following settings:
¡ Sub-option type: 80.
¡ Sub-option length: 0b. The length of 0000020a17c8010a17c802 is 11 bytes.
¡ Sub-option value: 0000020a17c8010a17c802. 0000 is a fixed part, 02 is the number of IPv4 AC addresses, 0a17c8010a17c802 is AC addresses 10.23.200.1 and 10.23.200.2 in hexadecimal format.
When you configure the PXE server address sub-option in the DHCP address pool view of the DHCP server, the configuration is option 43 hex 800b0000020a17c8010a17c802.
ACS parameter sub-option
About ACS parameter sub-option
This sub-option provides a DHCP client with ACS parameter information, including ACS URL, username, and password.
Table 2 shows the fields of ACS parameter sub-option
Table 2 Fields of ACS parameter sub-option
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Length |
Remarks |
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Sub-option type |
1 |
The value is fixed at 01, which represents ACS parameter sub-option. |
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Sub-option length |
1 |
This value specifies the length of the sub-option except for the Sub-option type field and the Sub-option length field, in bytes. |
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Sub-option value |
Variable length, which depends on the sub-option length. |
This value is in Hexadecimal IPv4 AC addresses format. You can configure up to 16 IPv4 addresses in a row. Do not use any space to separate them. For example, 0a17c801 and 0a17c8010a17c802. |
Configuration examples
· To configure an ACS parameter sub-option that contains IPv4 AC address 10.23.200.1, use the following settings:
¡ Sub-option type: 01.
¡ Sub-option length: 04. The length of 0a17c801 is 4 bytes.
¡ Sub-option value: 0a17c801, the AC address in hexadecimal format.
When you configure the ACS parameter sub-option in the DHCP address pool view of the DHCP server, the configuration is option 43 hex 01040a17c801.
· To configure an ACS parameter sub-option that contains IPv4 AC addresses 10.23.200.1 and 10.23.200.2, use the following settings:
¡ Sub-option type: 01.
¡ Sub-option length: 08. The length of 0a17c8010a17c802 is 8 bytes.
¡ Sub-option value: 0a17c8010a17c802, the AC addresses in hexadecimal format.
When you configure the ACS parameter sub-option in the DHCP address pool view of the DHCP server, the configuration is option 43 hex 01080a17c8010a17c802.
Option 43 sub-options supported by different vendors
When the DHCP server is attached to H3C APs, the support of the DHCP server for Option 43 sub-options varies by its vendor. This document only introduces the support of mainstream vendors for Option 43 sub-options. For the support of a third-party vendor for Option 43 and the configuration procedure, see the corresponding documents on the official website of that third-party vendor.
Table 3 Support for Option 43 sub-options
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Vendor |
PXE server address sub-option |
ACS parameter sub-option |
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H3C |
Supported |
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HUAWEI |
Supported |
Supported |
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Ruijie |
Supported |
Supported |
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Cisco |
Supported |
Supported |
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Juniper |
No supported |
No supported |
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Linux |
No supported |
No supported |
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Rukus |
Supported |
Supported |
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Extreme |
Supported |
Supported |
Option 43 configuration example for H3C DHCP servers
# Enter system view.
<Sysname> system-view
# Create address pool vlan100 and enter its view. This address pool is used for address assignment to APs.
[Sysname] dhcp server ip-pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
[Sysname-dhcp-pool-vlan100] option 43 hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
[Sysname-dhcp-pool-vlan100] option 43 hex 0104c0a86401
Option 43 configuration example for Huawei DHCP servers
# Enter system view.
<HUAWEI> system-view
# Create address pool vlan100 and enter its global view. This address pool is used for address assignment to APs.
[HUAWEI] ip pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
[HUAWEI-ip-pool-vlan100] dhcp server option 43 hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
[HUAWEI-ip-pool-vlan100] dhcp server option 43 hex 0104c0a86401
Option 43 configuration example for Ruijie DHCP servers
# Enter privileged EXEC mode.
# Enter global configuration mode.
Hostname# configure terminal
# Create address pool vlan100 and enter its view. This address pool is used for address assignment to APs.
Hostname(config)# ip dhcp pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
Hostname(dhcp-config)# option 43 hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
Hostname(dhcp-config)# option 43 hex 0104c0a86401
Option 43 configuration example for Cisco DHCP servers
# Create address pool vlan100 and enter its view. This address pool is used for address assignment to APs.
Device(config)# ip dhcp pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
Device(config-dhcp)# option 43 hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
Device(config-dhcp)# option 43 hex 0104c0a86401
Option 43 configuration example for Ruckus DHCP servers
# Enter global configuration mode.
device# configure terminal
# Create address pool vlan100 and enter its view. This address pool is used for address assignment to APs.
device(config)# ip dhcp-server pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
device(ip dhcp-server pool vlan100)# option vendor-encapsulated-options hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
device(ip dhcp-server pool vlan100)# option vendor-encapsulated-options hex 0104c0a86401
Option 43 configuration example for Extreme DHCP servers
# Create address pool vlan100 and enter its view. This address pool is used for address assignment to APs.
System(rw-config)-> ip dhcp pool vlan100
# Configure the PXE server address sub-option of Option 43. The AC IP address is 192.168.100.1.
System(rw-config-dhcp-pool)-> option 43 hex 8007000001c0a86401
# Configure the ACS parameter sub-option of Option 43. The AC IP address is 192.168.100.1.
System(rw-config-dhcp-pool)-> option 43 hex 0104c0a86401
