Page 210 7750 SR OS Services Guide
• 7750 SR will always reply to a received ARP request message from the Ethernet SAP with
the SAP MAC address and a source IP address of the IP address being ARPed without any
further check of the latter.
• If the router received an address list TLV from the remote PE node with a valid IP address
of the CE attached to the remote PE, it not checks it against the IP address being ARPed
for when replying to an ARP request over the Ethernet SAP.
• The ARP cache is flushed when the SAP bounces or when the operator manually clears
the ARP cache. This results in the clearing of the CE address discovered on this SAP.
However, when the SAP comes up initially or comes back up from a failure, an unsolicited
ARP request is not sent over the Ethernet SAP.
• If the Ipipe service makes use of a spoke SDP, the 7750 SR includes the address list TLV
in the interface parameters field of the pseudowire FEC TLV in the label mapping
message. The address list TLV contains the current value of the CE address in the ARP
cache. If no address was learned, then an address value of 0.0.0.0 must be used.
• If the remote PE included the address list TLV in the received label mapping message, the
local 7750 SR updates the remote PE node with the most current IP address of the
Ethernet CE using a T-LDP notification message with status TLV status code is set to
0x0000002C and containing an LDP address list. The notification message is sent each
time an IP address different from the current value in the ARP cache is learned. This
includes when the ARP is flushed and the CE address is reset to the value of 0.0.0.0.
• If the remote PE did not include the address list TLV in the received label mapping
message, the local router will not send any notification messages containing the address
list TLV during the lifetime of the IP pseudowire.
• If the operator disables the ce-address-discovery option under the VLL service, service
manager instructs LDP to withdraw the service label and the service is shutdown. The
pseudowire labels will only be signaled and the service will come up if the operator re-
enters the option again or enters manually the ce-address parameter under SAP and spoke
SDP.
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