service dhcp-server shared-network-name <name> subnet <ipv4net> failover
Enables DHCP failover functionality for a DHCP address pool on a subnet.
- name
- Mandatory. A DHCP address pool.
- ipv4net
- Mandatory. Multinode. The IPv4 network served by the DHCP address pool. The format is ip-addr/prefix.
Configuration mode
service {
dhcp-server {
shared-network-name name {
subnet ipv4net {
failover {
}
}
}
}
}
Use this command to enable DHCP failover for an address pool on a given network, allowing two DHCP servers to share an address pool.
In a failover configuration, two DHCP servers act as failover peers, with one of the peers designated as the primary and the other as the secondary. For DHCP failover to work, the following conditions must be met.
- Both peers must be vRouters and must be running the same version of Vyatta router software.
- Each server must be configured to point to the other as the failover peer.
- The time on the servers must be exactly synchronized.
- At least one IP address must exist in the start-stop range for each subnet that has not been either excluded (by using service dhcp-server shared-network-name name subnet ipv4net exclude ipv4) or statically mapped (by using service dhcp-server static-mapping mapname).
The system times should be synchronized before configuring DHCP failover. Use of NTP time synchronization is highly recommended. However, if difficulties arise because of incorrect system times, then disable NTP, reset the times correctly, and re-enable NTP.
Note that DHCP leases are assigned only in failover configurations if proper communication is established between the two failover peers. If the configuration is incorrect (if, for example, one failover peer is configured but the other is not), DHCP leases are not dispersed.
Note also that statically mapped addresses are not renewed by a failover server unless they are explicitly defined on that server by using service dhcp-server static-mapping mapname.
Use the set form of this command to define DHCP failover configuration.
Use the delete form of this command to remove DHCP failover configuration.
Use the show form of this command to view DHCP failover configuration.