The operator enables the following CE address dynamic learning procedures by enabling the ce-address-discovery option under the VLL service on the 7450 ESS or 7750 SR.
Allow the service to come up without the CE address parameter configured at both the SAP and spoke-SDP. If one or both parameters are configured, they are ignored.
The operator cannot configure the ce-address parameter under SAP or spoke-SDP when the ce-address-discovery option under the VLL service 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.
If the router receives an invFR ARP request message over the FR SAP, it updates the ARP cache with the FR CE address. It also replies with the IP address of the CE attached to the remote PE if a valid address was advertised in the address list TLV by this remote PE. Otherwise, the router updates the ARP cache but does not reply to the invFR ARP.
If the Ipipe service uses a spoke-SDP, the router 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 is used.
If the remote PE included the address list TLV in the received label mapping message, the local router updates the remote PE node with the most current IP address of the FR CE using a T-LDP status notification message 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 0.0.0.00.
If the remote PE did not include the address list TLV in the received label mapping message, the local router does not send any notification messages containing the address list TLV during the lifetime of the IP pseudowire.