Virtual Leased Line Services
7750 SR OS Services Guide Page 209
Extension to IP VLL for Discovery of Ethernet CE IP Address
VLL services provide IP connectivity between a host attached to a point to point access circuit
(FR, ATM, PPP) with routed PDU encapsulation and a host attached to an Ethernet interface. Both
hosts appear to be on the same IP interface. This feature is supported only for IPv4 payload.
In deployments where it is not practical for operators to obtain and configure their customer CE
address, the following behaviors apply:
• A service comes up without prior configuration of the CE address parameter under both
the SAP and the spoke SDP.
• Rely solely on received ARP messages from the Ethernet SAP attached CE device to
update the ARP cache with no further check of the validity of the source IP address of the
ARP request message and the IP address ARPed for.
• The LDP address list TLV to signal the learned CE IP address to the remote PE is
supported. This is to allow the 7750 SR PE with the FR SAP to respond to an invFR ARP
request message received from the FR attached CE device. Only Ethernet SAP and FR
SAP can learn the CE address via ARP and invFR ARP respectively. The 7750 SR does
not support invATM ARP on an ATM interface.
VLL Ethernet SAP Procedures
The operator can enable the following CE address discovery procedures by configuring the ce-
address-discovery in the config>service>ipipe context.
• The service is brought up without the CE address parameter configured at either the SAP
or the spoke SDP.
• The operator cannot configure the ce-address parameter under the
config>service>ipipe>sap or config>service>ipipe>spoke-sdp context when the ce-
address-discovery in the config>service>ipipe context is enabled. Conversely, the
operator is not allowed to enable the ce-address-discovery option under the Ipipe service
if it has a SAP and/or spoke SDP with a user-entered ce-address parameter.
• While an ARP cache is empty, the 7750 SR PE does not forward unicast IP packets over
the Ethernet SAP but forwards multicast/broadcast packets.
• The PE waits for an ARP request from the CE to learn both IP and MAC addresses of the
CE. Both entries are added into the ARP cache. The PE accepts any ARP request message
received over Ethernet SAP and updates the ARP cache IP and MAC entries with no
further check of the source IP address of the ARP request message or of the IP address
being ARPed.
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