| 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 ? |
