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June 2012

802.1d – STP

1. BPDUs – Bridge Protocol Data Units BPDUs are sent as 802.3 frames with a source address equal to the MAC address of the sending switch port and with a destination address of 01:80:C2:00:00:00. The LLC header has the DSAP and SSAP fields set to 0x42. Protocol ID is set …

MPLS 101

1. Labels MPLS (Multi Protocol Label Switching) adds a 4 Byte header between the Layer 2 and Layer 3 header for each label. The header has 4 fields: 20 bits – Label – locally significant on the link (similar to Frame Relay DLCI) 3 bits – EXP – used for …