Dell Force10 S4820T S4820T Configuration Guide - Page 859

Figure 43-6. TPID Match and First-byte Match on the E-Series TeraScale Building D INTERNET VLAN BLUE SERVICE PROVIDER TPID 0x9191 VLAN GREEN VLAN BLUE R2-E-Series TeraScale TPID: 0x9100 R1-E-Series TeraScale TPID: 0x9191 VLAN GREEN, VLAN PURPLE VLAN PURPLE VLAN RED R3-E-Series TeraScale TPID: 0x9100 TPID PCP CFI (0x9100) (0) Building B VID TPID PCP (VLAN Purple) (0x8100) Building C R4 R4-Non-Force10 System TPID: 0x9100 TPID PCP (0x8100) CFI VID (0) (VLAN Red) CFI VID (0) (VLAN Red) VLAN RED Building A TPID 0x8100 on E-Series TeraScale Systems E-Series TeraScale treats TPID 0x8100 as a normal VLAN even when on the outer tag. E-Series TeraScale makes forwarding decisions based strictly on the protocol type, without regard for whether the port is an access port. Therefore, when the outer tag has TPID 0x8100, the system does not remove it from frames egressing an access port. Still, although the frames cannot be decapsulated, the system is able to switch them. In Figure 43-7, the frame originating from Building A is double tagged on egress at R4 and is switched towards Building B, but is not decapsulated on egress at R2 because its TPID is 0x8181. FTOS Behavior: The E-Series ExaScale and TeraScale forward frames with TPID 0x8100 even when its own TPID is not 0x8100. This behavior is required to service ARP and PVST packets, which use TPID 0x8100. Service Provider Bridging | 859