Configuring the DHCP Server

The following commands allow you to configure the DHCP (Dynamic Host Configuration Protocol) server included in the switch.

Note

Configuring both the DHCP server and the DHCP client on the same VLAN and the same ports is not recommended.

The parameters available to configure include the IP address range, IP address lease, and multiple DHCP options. Until ExtremeXOS 15.1, the DHCP server had a limited set of known DHCP options it could send out on request, i.e., Default Gateway, DNS, and WINS server(s). General option support has been added in ExtremeXOS 15.2. This allows you to add support for any option needed, with no ExtremeXOS code changes. The three options mentioned above can also be overwritten to support a larger number of servers, if needed. This feature allows the switch administrator to add an option based on DHCP option code value, and support various was of setting the value.

Configure the range of IP addresses assigned by the DHCP server using the command:
configure vlan vlan_name dhcp-address-range ipaddress1 - ipaddress2
Remove the address range information using the command:
unconfigure vlan vlan_name dhcp-address-range
Set how long the IP address lease assigned by the server exists using the command:
configure vlan vlan_name dhcp-lease-timer lease-timer
Note

The ExtremeXOS DHCP server allows the configuration of a DHCP lease timer value greater than two seconds only. The timer value range is 3–4294967295. If the DHCP lease timer is not configured, the ExtremeXOS DHCP server offers an IP address with the default lease time of 7200 seconds.

Note
Maximum number of DHCP leases supported by the ExtremeXOS DHCP server is limited by the number of VLANs and IP address range configured on that VLAN, and there is no hardware/software limit for the DHCP leases.

Note
The maximum number of DHCP servers supported by ExtremeXOS is limited by the number of VLANs the ExtremeXOS switch supports.
To set the generic DHCP option code, default gateway, Domain Name Servers (DNS) addresses, or Windows Internet Naming Service (WINS) server, use the following command:
configure {vlan} vlan_name dhcp-options [code option_number [16-bit value1 {value2 {value3 {value4}}} | 32-bit value1 {value2 {value3 {value4}}} | flag [on | off] | hex string_value | ipaddress ipaddress1 {ipaddress2 {ipaddress3 {ipaddress4}}} | string string_value] | default-gateway | dns-server {primary | secondary} | wins-server] ipaddress
To remove the generic DHCP option code, default gateway, DNS server addresses, and WINS server information for a particular VLAN (Virtual LAN), use the following command:
unconfigure {vlan} vlan_name dhcp-options {[ default-gateway | dns-server {primary | secondary} | wins-server]}
Remove all the DHCP information for a particular VLAN using the command:
unconfigure vlan vlan_name dhcp

You can clear the DHCP address allocation table selected entries, or all entries.
Clear entries using the command:
clear vlan vlan_name dhcp-address-allocation [[all {offered | assigned | declined | expired}] | ipaddress]

You would use this command to troubleshoot IP address allocation on the VLAN.

Published March 2020prev | next

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