CCNA/CCNP preparation notes

by Andreas Ryf
OSI reference model
1: Physical Layer
2: Data Link Layer
3: Network Layer
4: Transport Layer
5: Session Layer
6: Presentation L.
7: Application Layer
IP Network Classes
Subnetting
Cables & fibres
Terms
Links
BCMSN
ONT

Layer 2: Data Link layer

 

Frames, MAC-addresses, LAN addressing, only locally valid addressing, not beyond the current subnet.

Broadcast domain

Token ring timing, Ethernet, ..

Bridges & switches

No retransmissions, no reception acknowledge

Packets have no defined time to live, in case of loops they can continue endlessly to travel on the network and totally congest it. They also might get multiplied.

STP, RSTP, MSTP, etc to avoid/resolve loops.


 

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