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📢 Personal study notes of CCNA & CCNP. Contents come from the YouTube channel Jeremy's IT Lab, Cisco official docs and AI.

▶️ Router Boost Order:

 Power on     Load Bootstrap     POST     Load IOS     Load startup configuration     Generate running configuration
+--------+->-+--------------+->-+----+->-+--------+->-+--------------------------+->-+------------------------------+
                  ROM            ROM       flash              NVRAM                              RAM

▶️ Table-1 Network Protocols and Techs

Abbr.	Names	Purposes	Key-concepts
STP	Spanning Tree Protocol	Prevent loops on layer2	PortFast, BPDU guard/filter, Root/Loop guard
DTP	Dynamic Trunking Protocol	Auto-configure switchport modess	Trunk/Access ports; native VLAN
VTP	VLAN Trunking Protocol	Propagate VLANs across switches	v2 vs v3
CDP	Cisco Discovery Protocol	Exchange neighbor devices info	Layer 2
NTP	Network Time Protocol	Synchronize time	Default stratum 8
NDP	Neighbor Discovering Protocol	Gather info required for IPv6 communication	5 ICMPv6 packet types
UDLD	Unidirectional Link Detection	Help STP to prevent layer2 loops	Unidirectional link

▶️ Table-2 Well-Know Multicast Addresses

Purpose	IPv4 Address	IPv6 Address
All nodes/hosts (like broadcast)	224.0.0.1	FF02::1
All routers	224.0.0.2	FF02::2
All OSPF routers	224.0.0.5	FF02::5
All OSPF DR/BDRs	224.0.0.6	FF02::6
All RIP routers	224.0.0.9	FF02::9
All EIGRP routers	224.0.0.10	FF02::A

▶️ Table-3 Special MAC Addresses

MAC Address	Destination for Protocols
01:00:0c:cc:cc:cc	CDP, VTP, DTP, PAgP, UDLD