local 7750 SR and 7450 ESS DHCP server
The DHCP server instantiated on the local 7750 SR and 7450 ESS node.
remote 7750 SR and 7450 ESS DHCP server
The DHCP server instantiated on the remote 7750 SR and 7450 ESS node (external to the local 7750 SR and 7450 ESS node).
3rd party DHCP server
The DHCP server external to any 7750 SR and 7450 ESS node and implemented outside of 7750 SR and 7450 ESS.
intercommunication link
The logical link between dual-homed 7750 SR and 7450 ESS DHCP servers used for synchronizing DHCP lease states. Multi-chassis Synchronization (MCS) protocol runs over this link. When this link is interrupted, synchronization of the leases between redundant DHCP servers is impaired. This link should be well protected with multiple underlying physical paths.
local IP address-range and prefix
The local failover mode in which the IP address-range and prefix is configured in dual-homed DHCP environment. The local keyword does not refer to the locality (local versus remote) of the server on which the IP address-range and prefix in configured, but rather refers to the ownership of the IP address-range and prefix. The DHCP server on which the local IP address-range and prefix is configured, owns this IP address-range and prefix and consequently can delegate the IP addresses and prefixes from it at any time, regardless of the state of the intercommunication link.
remote IP address-range and prefix
The remote failover mode in which the IP address-range and prefix is configured in dual-homed DHCP environment. The remote keyword does not refer to the locality of the server on which the IP address-range and prefix is configured but rather refers to the ownership of the IP address-range and prefix. The DHCP server on which the remote IP address-range and prefix is configured, but does not own this IP address-range and prefix during normal operation and consequently is not allowed to delegate the IP addresses and prefixes from it. Only when the intercommunication link between the two nodes transition into particular (failed) state, the DHCP server can start delegating new IP addresses from the remote IP address-range and prefix.
IP address-range and prefix ownership
The 7750 SR and 7450 ESS DHCP servers that can delegate new leases from an IP address-range and prefix that it owns. For example, an IP address-range and prefix designated as remote is not owned by the DHCP server on which it is configured unless specific conditions are met. Those conditions are governed by the state of the intercommunication link.
IP address-range and prefix takeover
The 7750 SR and 7450 ESS DHCP servers that do not own an IP address-range and prefix can take over the ownership of this IP address-range and prefix under specific conditions. When the ownership is taken, the new IP addresses can start being delegated from this IP address-range and prefix. Only the remote IP address-range and prefix can be taken over. Note that the takeover of an IP address-range and prefix has only local significance, in other words, the ownership is not taken away from some other DHCP server that has the same IP address-range and prefix designated as local. It only means that IP address-range and prefix that is configured as remote is available to takeover for new IP address delegation.
local PPPoX address pools
The method of accessing an IPv4/v6 address pool in 7750 SR and 7450 ESS DHCP4/6 server. For PPPoX clients, the IPv4/v6 addresses are allocated from those pools without the need for an intermediate DHCP relay-agent (7750 SR and 7450 ESS internal DHCP relay-agent). Although those pools are part of the local DHCP server in 7750 SR and 7450 ESS, the method of accessing them is substantially different than accessing local DHCP address pools for IPoE (DHCP) clients. IPoE (DHCP) and PPPoX hosts can share the same pool and yet each client type can access them in their own unique way:
IPoE client by DHCP messaging
PPPoE by internal API calls
local PPPoX pool management
The IPv4 address allocation/management for PPPoX clients independent of DHCP process (DHCP lease state). An IPv4 address allocated by local PPPoX Pool Management is tied to the PPPoX session. It is without the need for an internal DHCP relay-agent.