Switching (UD Notes)

Switch Receives Frame:

  • Forward
  • Filter (drop)
  • Flood (send everywhere exact back where it came from) (unicast)

Builds MAC Address table

  • Two mac address are contained in every frame, source and destination.
  • Source Mac Address are used to build table
  • Uses static entries with port
  • Dynamically is usually best


Hubs, Bridges, Switches (UD Notes)


  • one collision domain consisting of all connected hosts
  • one broadcast domain containing those same hosts
  • allows only one host to transmit at a time


  • logically segment the network
  • lessen the size of colisison domains
  • does nothing to segment broadcast domains


  • bring us one host collision domains
  • logically segment broadcast domain
  • not done by default



OSI and Data Units (UD NOTES)

7.  Application

6.  Presentation

5.  Session

4.  Transport

3.  Network

2.  Data Link

1.  Physical


Application/Presentation/Session Layers – don’t have associated unit. Data is Data

Transport Layer – segments

Network – Packets

Data Link Layer – Frames

Physical – Bits (ones and zeros)


Troubleshooting (CRAM Notes)

Troubleshooting Methodology

  • Problem Isolation – determining at what layer of the OSI model and on what device and links the problem may occur
  • Documentation – document the processes you use and the information you find
  • Resolve – find the root cause after isolation, document what happened, fix the root cause of the problem, fix the problem
  • Escalate – if you can’t fix the issue, send a written escalation to organization or third party with as much info as possible
  • Verify and Monitor – carefully verify and monitor your solution to ensure the issue are tury resolved

OSI Model

  • It is important to follow the OSI model using either a top down or bottom up approach depending on specific issues.
  • Review
    • Application
    • Presentation
    • Session
    • Transport
    • Network
    • Data Link
    • Physical

Please     Do     Not     Throw     Sausage     Pizza     Away

The Cable Table (CRAM Notes)

 Common Name  Speed  Standard  Cable Type, Max Length
 Ethernet  10 MBPS  10Base-T  Copper, 100m
 Fast Ethernet 100 MBPS  100Base-T  Copper, 100m
 Gigabit Ethernet 1000 MBPS 1000Base-LX Fiber, 5000m
 Gigabit Ethernet 1000 MBPS 10000Base-T Copper, 100m
 10 Gig Ethernet 10 GBPS 10GBase-T Coppper, 100m
40 Gig Ethernet 40 GBPS 40GBase-LR4 Fiber, 10000m

show controllers to check  the type or health of cables

Modern Cisco Switches support auto-mdix which allows you not to worry so much about the cables connecting the devices. But for the test you have to know this:

straight-through – unlike devices

crossover – for like devices

UTP – unshielded twisted pair is common.

DTE – data terminal equipment.

DCE – data communications equipment.



Collapsed Core & Three Tier Architecture (CRAM Notes)

Cisco break up networks into three easy to manage layers to tiers.

Access Layer – Provides workgroup/user access to the network as a result this layer is sometimes called the workstation layer.

Distribution Layer – policy based connectivity and controls the boundary between the access and the core layers

Core Layer – fast transport between distribution switches within the enterprise campus. called the bone layer

Access Layer

  • Layer 2 Switching
  • Port Security
  • QoS classification and marking and trust boundaries
  • ARP
  • VACLs
  • Spanning Tree
  • PoE and auxiliary VLANs for VoIP

Distribution Layer

  • Aggregation of Lan or WAN links
  • Policy-based security in the form of ACLs and filtering
  • Routing services between LANs and VLANs between routing domains
  • Redundancy and load balancing
  • Boundary for route aggregation and summarization configured on interfaces towards the core layer.

The Core Layer

  • Providing high-speed switching.
  • Providing reliability and fault tolerance


Collapsed Core Design takes the functions of the distribution layer and moves them (collapses) them into the core layer.


Cloud Resources on Enterprise Network Architecture (CRAM Notes)

Cloud services

  • Can be requested on demand
  • Can dynamically scale
  • Use a pool of resources
  • Offer variety of network access options
  • Can be measured and billed back to the user

Cloud Technology

  • IaaS – cloud provider makes available to the client – hardware, software, servers, storage, other infrastructure components
  • SaaS – cloud provider makes powerful software available to clients.
  • PaaP – cloud provider makes virtual machines available to clients virtual machines so that they can develop software applications in a test environment. Software development tools are also provided as a part of the platform.
  • XaaS – Any aspect of IT that is delivered through the cloud model