Cisco2 (LV)

8 flashcards · Other · by Emanuel Gostner

1. What sublayers in Layer2?

   MAC Control: Optional. Between LLC and MAC. More Flow control possibilities. LLC (Logical Link Control) 802.2: - encapsulates L3 - retransmits unsuccessful frames MAC (Medium Access Control)802.3: - encapsulates LLC Detects errors and discards frames

2. L1/L2 devices. Why L2 better choice?

   L1: Hubs, Repeater -> one large colission domain ex: if hubs are connected into extended star L2: Switch, Bridge -> boundary for colissions -> switch only divides colission domains if vlans are defined, otherwise not.

3. How do mac tables work?

   MAC<->Port Filter: Switch discards frame. dest. address in network frame came from (address already in table) Forward: Forwards the frame (Address known) Flood: Unicast to every host, except the node it came from (no broadcast because broadcast would be accepted-hosts have to check instead)

4. What does Switch do with broadcast frame?

   It sends the frame to every host except to the node it came from

5. Collision domains?

6. Difference Switch/Bridge

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7. Difference legacy/todays Ethernet

   10BaseT (legacy Ethernet) 10Mbps 100BaseT (Fast Ethernet) 100Mbps 1000BaseT (Gigabit Ethernet) 1000Mbps Today Ethernet: - Full-duplex: no collisions anymore

8. Reasons Ethernet's success

   Various L1 implementations (different cabling) but frame stays the same and operates the same way with upper layers simple, inexpensive, flexible easy to maintain interworks easily with TCP/IP Has been able to evolve without throwing out all existing software/hardware