Month: December 2017

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

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

Bridge

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

Switch

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

 

 

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 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

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.

 

 

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 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