Chap 22 - Enterprise Network Architecture Flashcards
What are the 3 layers of a hierarchical LAN design?
- Core (or backbone)
- Distribution Layer
- Access Layer
What does the Access Layer do?
Gives endpoints and users direct access to the network.
What does the Distribution Layer do?
Provides an aggregation point for the access layer and acts as a services and control boundary between the access layer and the core layer.
What does the Core Layer do?
Provides connections between distribution layers for large environments.
What is another name for the Access Layer?
Network Edge
What is another name for the Core Layer?
Backbone
What is QoE
Quality of Experience
What kind of devices can be used to extend the Access Layer out one more layer?
Wireless Access Points and IP phones
What are 3 reasons for segmenting the access layer?
- Performance
- Management
- Security
How does communication between endpoints on different access layer switches occur?
Through the Distribution Layer
What 3 roles does the Access Layer perform?
- Protects the network from malicious attacks
- Prevents endpoints from accessing unauthorized services
- Provides the trust boundary for QOS giving end users QoE
What is the primary function of the Distribution Layer?
To aggregate access layer switches in a given building or campus.
What boundary does the Distribution Layer provide?
The boundary between the Layer 2 domain of the access layer and the core’s Layer 3 domain.
What does the Distribution Layer boundary do on the layer 2 side and on the layer 3 side?
- On the Layer 2 side, it creates an STP boundary that limits propagation of Layer 2 faults
- On the Layer 3 side, it summarizes IP routes before they enter the core
What are 2 reasons for summarizing Layer 3 information at the Distribution Layer?
- Reduces IP routing tables for easier troubleshooting
- Reduces protocol overhead for faster recovery from failures
What are 2 guidelines for deploying Distribution Switches?
- Always in pairs
- With a layer 2 or layer 3 connection between them
Why are Distribution Switches deployed in pairs?
For redundancy
Why are multiple distribution layer switches required when access layer switches are located in multiple geographically dispersed buildings?
To reduce the number of costly fiber runs between buildings..
What 4 services does the Core provide?
- Aggregation point for multiple networks
- Connectivity between the access layer and other network blocks
- High-speed connectivity for enterprises with multiple campus networks
- High availability, scalability and fast convergence to the network
At what point should an organization consider implementing a Core Layer?
As networks grow beyond three distribution layers in a single location.
How does the Core Layer reduce complexity of network connections?
The core layer reduces the network complexity, from N × ( N − 1) to N links for N Distribution layers
What are 6 Enterprise Architecture Options?
- Two-tier design (collapsed core)
- Three-tier design
- Layer 2 access layer (STP-based)
- Layer 3 access layer (routed)
- Simplified campus design
- Software Defined Access (SD-Access)
What 3 things need to be considered before settling on a Collapsed Core design?
- Future scale
- Expansion
- Manageability
Who are the ‘Big Three’ cloud service providers?
- Amazon AWS
- Microsoft Azure
- Google Cloud Platform
What 4 things is the WAN Edge Block used to connect to?
- Remote data centers
- Remote branches
- Other campus networks
- Cloud connectivity using dedicated interconnections.
What 5 things are in the Data Center / Server Room Block?
- Business-critical servers
- Storage
- Big data processing
- Backup services
- E-commerce transactions
What 5 things is the Internet Edge Block used for?
- Regular Internet access
- E-commerce
- Connection to remote branches (outbound VPN)
- Remote VPN access (inbound VPN)
- Cloud provider connectivity that does not require dedicated interconnections.
What are 4 things that would be in the Network Services Block?
- Wireless LAN controllers (WLCs)
- Cisco Identity Services Engine (ISE)
- Cisco TelePresence Manager
- Cisco Unified Communications Manager (CUCM).
What are 3 times when multiple pairs of Distribution switches would be required?
- Large campus with multiple buildings
- When high density of WAN routers, Internet edge devices, data center servers, and network services are causing poor network performance
- When access switches across many buildings require more fiber interconnects back to a single collapsed core
What is a PIN?
Place In the Network
What 4 things describe the Spine-Leaf design?
- Nexus 7k is spine, FEX is leaf
- STP replaced with L3 routing
- Every leaf is connected to every spine switch
- Spine never connects to spine and leaf never connects to leaf
In a Layer 2 Access Layer (STP based) design what is considered a loop-free design?
When a VLAN is restricted to a single switch.
In a Layer 2 Access Layer (STP based) design what is considered a looped design?
When all VLANs are available on all switches
What are 2 disadvantages of a Layer 2 Access Layer (STP based) looped design?
- Bandwidth reduced due to STP blocked ports
- Causes slower convergence
In a Layer 2 Access Layer (STP based) design where is layer 3 done?
On the distribution switches
In a Layer 2 Access Layer (STP based) design how is high availability achieved in layer 3?
By running an FHRP on the distribution layer
What is a downside to running a FHRP on the Distribution Layer?
It only allows hosts to send data to the active FHRP router using a single access uplink, which leaves the other uplink unutilized.
How can load balancing be done with an FHRP?
Odd VLANs are active on one distribution layer switch, even VLANs active on the other
What is the upside and downside to using GLBP?
- It provides greater uplink utilization for access layer-to-distribution layer traffic by load balancing the load from hosts across multiple uplinks
- The downside is that it works only on loop-free topologies.
What is Layer 3 Access Layer (Routed Access)?
Routed access is a configuration in which Layer 3 is extended all the way to the access layer switches
What are 5 advantages of the Layer 3 Access Layer (Routed Access) alternative?
- No FHRP required
- No STP required
- Increased uplink utilization
- Easier troubleshooting
- Faster convergence
What are 2 disadvantages of the Layer 3 Access Layer (Routed Access) design?
- It does not support spanning VLANs across multiple access switches
- Layer 3 switches cost more than Layer 2 switches
What 2 technologies are used in the Simplified Campus Design?
- Clustering technology such as VSS to make 2 switches appear as 1
- Stacking technology such as Stackwise to make multiple switches appear as 1
Can Clustering and stacking technologies be applied to any of the campus building blocks to simplify them even further.
Yes
What are the 7 advantages to using the Simplified Campus Design?
- Simplified design
- No FHRP required
- Reduced dependence on STP
- Increased uplink utilization
- Easier troubleshooting
- Faster convergence
- Distributed VLANs
When is a Leaf-Spine network a good alternative?
When traffic is mostly east-west
In a Leaf-Spine design how are routes configured?
Equal Cost Multipathing
