In typical routing behavior, the system uses the IP route table to select the egress interface, an ARP entry is used forward the packet to the appropriate Ethernet MAC. With R-VPLS, the egress IP interface may be represented by multiple egress (VPLS service SAPs).
The following table describes how the ARP cache and MAC FIB entry states interact.
ARP Cache entry |
MAC FIB entry |
Routing or system behavior |
|---|---|---|
ARP Cache Miss (No Entry) |
Known or Unknown |
Triggers a request to control plane ARP processing module, to send out an ARP request, out of all the SAPs. (also known as virtual ports) of the VPLS instance. |
ARP Cache Hit |
Known |
Forward to specific VPLS virtual port or SAP. |
Unknown |
This behavior cannot happen typically on 7210 SAS-D, as and when an Layer 2 entry is removed from the FDB, the matching MAC address is also removed from the ARP cache. On 7210 SAS-K, the packet is sent out of all the SAPs of the VPLS instance. |