Cisco Stuff

Cisco L2 Protocols

Collected some magic numbers that Cisco uses in their L2 management protocols e.g. CDP.These are transported in Ethernet 802.2 LLC/SNAP frames. The Ethernet destination address is a Cisco multicast one. 01-00-0C-XX-XX-XX. The SNAP header comprises OUI 00-00-0C and protocol IDs below.

Protocol Cisco Protocol ID Ethernet multicast
ISL N/A 01-00-0C-00-00-00
CDP 0x2000 01-00-0C-CC-CC-CC
VTP 0x2003 01-00-0C-CC-CC-CC
DTP 0x2004 01-00-0C-CC-CC-CC
UDLD 0x0111 01-00-0C-CC-CC-CC
PAgP 0x0104 01-00-0C-CC-CC-CC
Shared Spanning Tree SSTP 0x010B 01-00-0C-CC-CC-CD
UplinkFast 0x200A 01-00-0C-CD-CD-CD
Inter-VLAN bridging 0x010C 01-00-0C-CD-CD-CE
CGMP 0x2001 01-00-0C-DD-DD-DD
Cisco SYNC (STP) 0x2006 01-00-0C-EE-EE-EE

FIXME: Does anyone have a full list of Cisco LLC/SNAP protocol IDs? Good information from Cisco: here.

Standard L2 Protocols

Spanning-tree: BPDUs use ethernet 01-80-C2-00-00-00 multicast. Use 802.2 LLC frames with DSAP = SSAP = 0x42.

Ethernet flow-control PAUSE: 01-80-C2-00-00-01

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