Operation Manual – VLANH3C S7500 Series Ethernet Switches Chapter 1 VLAN Overview1-8DA&SA(12) Length(2) DSAP(1) SSAP(1) Control(1) OUI(3) DataPID(2)tFigure 1-8 802.2 SNAP encapsulation formaIn 802.2 SNAP encapsulation format, the values of the DSAP field and the SSAP fieldare always AA, and the value of the control field is always 3.The switch differentiates between 802.2 LLC encapsulation and 802.2 SNAPencapsulation according to the values of the DSAP field and the SSAP field.Note:When the OUI is 00-00-00 in 802.2 SNAP encapsulation, the PID field has the samemeaning as the type field in Ethernet II encapsulation, which both refer to globallyunique protocol number. Such encapsulation is also known as SNAP RFC 1042encapsulation, which is standard SNAP encapsulation. The SNAP encapsulationmentioned in this chapter refers to SNAP RFC 1042 encapsulation.1.3.3 Procedure for the Switch to Judge Packet ProtocolBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcReceive packetsType (length ) field0x6000 to 0x05DC0x6000x6000x600 0x05DC to 0x0600 Invcalid packets thatannot be matched802.3 encapsulationControl field Invalid packcannot beValue is 3Value is not 3 ets thatmatchedsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnap encapsulationllc encapsulation0x6000x6000x600Ethernet IIencapsulationMatch thetype value0x600 to 0xFFFControlBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcDsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcReceive packetsType (length ) field0x6000 to 0x05DC0x6000x6000x600 0x05DC to 0x0600 Invc802.3 encapsulation802.3 encapsulationalid packets thatannot be matchedControl field Invalid packcannot beValue is 3Value is not 3 ets thatmatchedsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnap encapsulationllc encapsulation0x6000x6000x600Ethernet IIencapsulationMatch thetype value0x600 to 0xFFFControlBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcDsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcReceive packetsType (length ) field0x6000 to 0x05DC0x6000x6000x600 0x05DC to 0x0600 Invcalid packets thatannot be matched802.3 encapsulation802.3 encapsulationControl field Invalid packcannot beValue is 3Value is not 3 ets thatmatchedsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnap encapsulationllc encapsulation0x6000x6000x600Ethernet IIencapsulationMatch thetype value0x600 to 0xFFFControlBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcDsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcBoth are AABoth are FF Dsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcDsapssap snapllcMatch dsapand ssap valueMatchtypeOther valuessnapllcsnapllcsnapllcReceive packetsType (length ) field0x6000 to 0x05DC0x6000x6000x600 0x05DC to 0x0600 Invc802.3 encapsulation802.3 encapsulationalid packets thatannot be matchedControl field Invalid packcannot beValue is 3Value is not 3 ets thatmatchedsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcRawencapsulationsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnapllcsnap encapsulationllc encapsulation0x6000x6000x600Ethernet IIencapsulationMatch thetype value0x600 to 0xFFFControlFigure 1-9 Procedure for the switch to judge packet protocol
