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level: Chapter 2

Questions and Answers List

level questions: Chapter 2

QuestionAnswer
what were switches called ?- First were called “Bridges” and had Bridge Tables - Bridges had low port Density
what are switches advantages ?- Have MAC Learning based on the Device port - Have MAC Tables - Forwards Frames based on the MAC Table - Have a Look-up Engine - Look-up one frame only at a time!!!!! (How fast?) - Do Schedule Frame forwarding
MAC table filled (learned) based on what ?on the Source MAC The Dynamic Entry
MAC table decision is taken, based on what ?on the Destination MAC
What will happen if Destination MAC is unknown ?FLOODING ! and to solve that MAC table limits the time of every MAC address .
what is VLAN ?A VLAN (virtual LAN) is a subnetwork which can group together collections of devices on separate physical local area networks (LANs) .
in VLANs , Every single switch port must become either ________ or ________ ?Access or Trunk port
what is Access port ?Access Ports: every switch port that is connected to an End device, NO Tags will Cross
what is Trunk port ?Trunk Ports: every switch port that must carry more than on tag
VLAN Types ?- Data VLAN: Ordinary - Voice VLAN: Voice data only (higher priority) - Default and Native VLAN: NO TAGS
what ir turnking ?Trunking: I need more than 1 VLAN to cross a link - Done by using encapsulation (DOT1Q)
We need redundancy, but there will be a broadcast message! What will happen?“LOOP”, AKA “Broadcast Storm”
Then how can we prevent what is called a “LOOP”, AKA “Broadcast Storm”?STP , Spanning Tree Protocol
process of STP ?1- choose Root Bridge by : - check lowest Bridge priority . -if bridge priority was the same ,check lowest MAC address. 2- determine Designated port ,Forwarding state 3-determine Root port ,Forwarding state 4-determine alternative or Blocked port, Blocking State The entire process of election takes (30 – 50) Seconds
what is bridge ID ?bridge ID = priority value . MAC address
how STP works ?disable -> listening -> learning -> forwarding or blocking this type use 802.1D
how Rapid STP (RSTP) works (v2) ?Rapid STP: NO Listening, NO Blocking, only (Discard, Forwarding, Learning) use 802.1w Then delay will become = 3 + 3 = 6 Seconds
what is PVST (another version ) ?There will be a Per-VLAN STP (PVST) Each VLAN can have an ELECTION!! Each VLAN will have its own root! Things are much better now Specially that there is a RPVST+ (faster)!
what is CDP and LLDP ?- CDP and LLDP do Discovery negotiations between devices - Detailed information about the neighbor - My port that is connected to it - Its port that is connected to me - The IP Address of the neighbor device - The MAC Address of the neighbor device - Port description of the neighbor but CDP for cisco and LLDP open standard form IEEE
what is MST ?multiple spanning tree : uses Edge port and port fast . Edge ports : ports not included in elections port fast :included in elections .
What if the bandwidth of an interface is not enough?LACP can Aggregate/Bundle multiple interfaces into a single new interface Link Aggregation Control Protocol. Done by negotiating between the two devices using the LACP protocol and Device Role. - Watch out for both devices, at least one of them must be ACTIVE - Load Balancing Mechanism: by default = src-dst-mac - Both Layer2 (Switches) and L3 (Routers) LACP can be done, But in L3: no need for Negotiating and Device Roles ?