(Optional) Configuring User-defined Options
Context
- Based on the options in DHCP Discovery messages
The device inserts an option configured using the dhcp server option (based on an interface address pool) or option (based on a global address pool) command into DHCP Reply messages to be sent to a client only when the client requests this option.
- By forcibly appending the option field
The device inserts an option configured using the dhcp server force insert option (based on an interface address pool) or force insert option (based on a global address pool) command into DHCP Reply messages to be sent to a client regardless of whether the client requests this option.
Procedure
- Configure user-defined options based on an interface address pool.
- Enter the interface or sub-interface view.
interface interface-type interface-number[.subinterface-number ]
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731S-H, S5731-S, S5731S-S, S6720-HI, S5732-H, S6730-H, S6730S-H, S6730-S, S6730S-S, S6720-EI, and S6720S-EI support sub-interfaces.
- (Optional) On an Ethernet interface, run undo portswitch
The interface is switched to Layer 3 mode.
By default, an Ethernet interface works in Layer 2 mode.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
- Configure user-defined options.
dhcp server option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }
By default, no user-defined option is configured.
If an option carries a password, the option code in ascii or hex type is insecure. Therefore, you are advised to set the option code type to cipher. For security purposes, use a password that is at least six characters long and contains at least two types of the following: lowercase letters, uppercase letters, digits, and special characters.
After an option is configured, the device inserts the option into DHCP Reply messages to be sent to clients only when the clients request this option.
Not all options can be configured using the preceding command. The following table lists the options and their commands.Table 1 Commands for configuring options Option
Configuration Command
Description
Option1
mask-length in the ip address ip-address { mask | mask-length } command
Subnet mask
Option3
ip-address in the ip address ip-address { mask | mask-length } command
Gateway address
Option6
dhcp server dns-list ip-address &<1-8>
DNS server IP address
Option15
dhcp server domain-name (interface view) domain-name
Domain name
Option44
dhcp server nbns-list ip-address &<1-8>
NetBIOS server IP address
Option46
dhcp server netbios-type { b-node | h-node | m-node | p-node }
NetBIOS node type
Option50
N/A
Requested IP address
Option51
dhcp server lease { day day [ hour hour [ minute minute ] ] | unlimited }
IP address lease
Option52
N/A
Additional option
Option53
N/A
DHCP message type
Option54
N/A
Server identifier
Option55
N/A
Parameter request list
Option57
N/A
Maximum length of a DHCP message
Option58
N/A
Lease renewal time (T1), which is 50% of the lease time
Option59
N/A
Lease renewal time (T2), which is 87.5% of the lease time
Option61
N/A
Client identifier
Option82
N/A
Relay agent information
Option120
dhcp server sip-server { ip-address ip-address &<1-2> | list domain-name &<1-2> }
SIP server IP address
Option121
dhcp server option121 ip-address { ip-address mask-length gateway-address } &<1-8>
A group of classless routes
Option184
dhcp server option184 { as-ip ip-address | fail-over ip-address dialer-string | ncp-ip ip-address | voice-vlan vlan-id }
Voice parameters
- Enter the interface or sub-interface view.
- Configure user-defined options based on a global address pool.
In the global address pool view:
- Enter the system view.
system-view (Optional) Enable the DHCP server to trust Option 82.
dhcp server trust option82By default, the device is enabled to trust Option 82.
- Enter the global address pool view.
ip pool ip-pool-name
(Optional) Force the DHCP server to insert a specified option field into DHCP Reply messages.
force insert option code &<1-254>
By default, the DHCP server does not forcibly insert a specified option field into DHCP Reply messages.
Configure user-defined options.
option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }
By default, no user-defined option is configured.
If an option carries a password, the option code in ascii or hex type is insecure. Therefore, you are advised to set the option code type to cipher. For security purposes, use a password that is at least six characters long and contains at least two types of the following: lowercase letters, uppercase letters, digits, and special characters.
Not all options can be configured using the preceding command. The following table lists the options and their commands.Table 2 Commands for configuring options Option
Configuration Command
Description
Option1
mask-length in the network (IP address pool view) ip-address [ mask { mask | mask-length } ]
Subnet mask
Option3
gateway-list ip-address &<1-8>
Gateway address
Option6
dns-list ip-address &<1-8>
DNS server IP address
Option15
domain-name domain-name
Domain name suffix
Option44
nbns-list ip-address &<1-8>
NetBIOS server IP address
Option46
netbios-type { b-node | h-node | m-node | p-node }
NetBIOS node type
Option50
N/A
Requested IP address
Option51
lease { day day [ hour hour [ minute minute ] ] | unlimited }
IP address lease
Option52
N/A
Additional option
Option53
N/A
DHCP message type
Option54
N/A
Server identifier
Option55
N/A
Parameter request list
Option57
N/A
Maximum length of a DHCP message
Option58
N/A
Lease renewal time (T1), which is 50% of the lease time
Option59
N/A
Lease renewal time (T2), which is 87.5% of the lease time
Option61
N/A
Client identifier
Option82
N/A
Relay agent information
Option120
sip-server { ip-address ip-address &<1-2> | list domain-name &<1-2> }
SIP server IP address
Option121
option121 ip-address { ip-address mask-length gateway-address } &<1-8>
A group of classless routes
Option184
option184 { as-ip ip-address | fail-over ip-address dialer-string | ncp-ip ip-address | voice-vlan vlan-id }
Voice parameters
- Enter the system view.
In the DHCP Option template view:
- Enter the system view.
system-view Create a DHCP Option template and enter the DHCP Option template view.
dhcp option template template-name
By default, no DHCP Option template is created.
To allocate network parameters except IP addresses to static clients, configure a DHCP Option template. Network parameters configured in the DHCP Option template view take effect only for static clients. For static clients, if a network parameter is configured in both the DHCP Option template view and global address pool view, only the configuration in the DHCP Option template view takes effect.
To allocate only IP addresses to static clients (for details, see (Optional) Configuring Fixed IP Addresses in an Address Pool), you do not need to configure a DHCP Option template.
(Optional) Force the DHCP server to insert a specified option field into DHCP Reply messages.
force insert option code &<1-254>
By default, the DHCP server does not forcibly insert a specified option field into DHCP Reply messages.
Configure user-defined options.
option code [ sub-option sub-code ] { ascii ascii-string | hex hex-string | cipher cipher-string | ip-address ip-address &<1-8> }
By default, no user-defined option is configured.
If an option carries a password, the option code in ascii or hex type is insecure. Therefore, you are advised to set the option code type to cipher. For security purposes, use a password that is at least six characters long and contains at least two types of the following: lowercase letters, uppercase letters, digits, and special characters.
Not all options can be configured using the preceding command. See Table 2 for the list of options and their commands.
Configure a classless static route to be allocated to clients.
option121 ip-address { ip-address mask-length gateway-address } &<1-8>
By default, no classless static route to be allocated to DHCP clients is configured.
Configure Option 184.
option184 { as-ip ip-address | fail-over ip-address dialer-string | ncp-ip ip-address | voice-vlan vlan-id }
By default, the Option 184 field is not configured.
If you need to configure other items in the DHCP Option template view, complete them first before performing the following steps.
- (Optional) Return to the system view.
quit - (Optional) Enter the global address pool view.
ip pool ip-pool-name
- (Optional) Bind a DHCP Option
template to static clients.
static-bind ip-address ip-address mac-address mac-address option-template template-name
- Enter the system view.