Alcatel-Lucent 7750 SR Manual page 745

The ARP reply agent only responds if the ARP request enters an interface (SAP, spoke SDP or mesh-
SDP) associated with the VPLS instance of the SAP.
A received ARP request that is not in the ARP reply agent table is flooded to all forwarding interfaces
of the VPLS capable of broadcast except the ingress interface while honoring split-horizon
constraints.
Static hosts can be defined on the SAP using the host command. Dynamic hosts are enabled on the
system by enabling the lease-populate command in the SAP's dhcp context. In the event that both a
static host and a dynamic host share the same IP and MAC address, the VPLS ARP reply agent will
retain the host information until both the static and dynamic information are removed. In the event
that both a static and dynamic host share the same IP address, but different MAC addresses, the VPLS
ARP reply agent is populated with the static host information.
The arp-reply-agent command will fail if an existing static host on the SAP does not have both
MAC and IP addresses specified. Once the ARP reply agent is enabled, creating a static host on the
SAP without both an IP address and MAC address will fail.
The ARP-reply-agent may only be enabled on SAPs supporting Ethernet encapsulation.
The no form of the command disables ARP-reply-agent functions for static and dynamic hosts on the
SAP.
Default not enabled
Parameters
sub-ident — Configures the arp-reply-agent to discard ARP requests received on the SAP that are
targeted for a known host on the same SAP with the same subscriber identification.
Hosts are identified by their subscriber information. For DHCP subscriber hosts, the subscriber hosts,
the subscriber information is configured using the optional subscriber parameter string.
When arp-reply-agent is enabled with sub-ident:
force-l2pt-boundary
Syntax [no] force-l2pt-boundary
Context config>service>vpls>sap
Description Enabling force-l2pt-boundary will force that all SAPs managed by the given m-vpls instance on the
corresponding port will have to have l2pt-termination enabled. This command is applicable only to
SAPs created under m-vpls and this regardless the flavor of STP currently being active. It is not
applicable to spoke-sdps.
7750 SR OS Services Guide
• If the subscriber information for the destination host exactly matches the subscriber information
for the originating host and the destination host is known on the same SAP as the source, the
ARP request is silently discarded.
• If the subscriber information for the destination host or originating host is unknown or undefined,
the source and destination hosts are not considered to be the same subscriber. The ARP request is
forwarded outside the SAP's Split Horizon Group.
• When sub-ident is not configured, the arp-reply-agent does not attempt to identify the subscriber
information for the destination or originating host and will not discard an ARP request based on
subscriber information.
Virtual Private LAN Services
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