Ch 22: Enterprise Network Architecture Flashcards
Which of the following best describe the hierarchical LAN design model? (Choose all that apply.)
- It allows for easier troubleshooting.
- It is highly scalable.
- It provides a simplified design.
- It offers improved performance.
- It is the best design for modern data centers.
- It allows for faster problem isolation.
A, B, C, D, and F. The benefits of a hierarchical LAN design include the following:
- It is highly scalable.
- It provides a simplified design.
- It offers improved performance.
- It allows for faster problem isolation.
- It provides cost-effective redundancy.
The best design for modern data centers with east-west traffic patterns is a leaf-spine architecture.
The access layer is also commonly referred to as the _____.
- endpoint layer
- aggregation layer
- end-user layer
- network edge
4.
The access layer, also commonly referred as the network edge, is where end-user devices and endpoints connect to the network.
What is the maximum number of distribution switches that can be deployed within a hierarchical LAN design building block?
- Four
- Two
- Six
- No limit
2.
In a hierarchical LAN design, distribution layer switches are deployed in pairs within a building blocks or places in the network (PINs).
Which of the following enterprise network architectures is also known as the collapsed core?
- Three-tier design
- Simplified campus design
- Two-tier design
- Leaf–spine design
3.
Small campus networks that don’t require an independent core can collapse the core function into the distribution layer. This is known as a two-tier, or collapsed core, design.
Which network blocks can provide access to cloud providers for end users? (Choose two.)
- WAN edge
- Internet edge
- Network services edge
- Data center
1 and 2.
The WAN edge can provide dedicated interconnections to cloud provid- ers, and the Internet edge can provide cloud provider connectivity not requiring dedicated interconnections.
Which technologies are used to deploy a simplified campus design? (Choose all that apply.)
- Clustering technologies
- Stacking technologies
- Virtual switching systems (VSSs)
- StackWise
- Daisy-chaining
A, B, C, and D.
A simplified campus design relies on switch clustering such as virtual switching systems (VSSs) and stacking technologies such as StackWise, in which multiple physical switches act as a single logical switch.
T/F: A collapsed core is a core/distribution layer fusion.
True.
Collapsing the core function into the distribution layer can be a cost-effective solution (as no core layer means no core layer devices) that requires no sacrifice of most of the benefits of the three-tier hierarchical model. Prior to selecting a two-tier collapsed core and distribution layers, future scale, expansion, and manageability factors need to be considered.
Figure 22-7 illustrates the two-tier design with the distribution layer acting as a collapsed core.
At what point is a core layer recommended? i.e. How many distribution layer switches warrant a separate core?
Three-tier designs separate the core and distribution layers and are recommended when more than two pairs of distribution switches are required. Multiple pairs of distribution switches are typically required for the following reasons:
- When implementing a network for a large enterprise campus composed of multiple buildings, where each building requires a dedicated distribution layer
- When the density of WAN routers, Internet edge devices, data center servers, and network services are growing to the point where they can affect network performance and throughput
- When geographic dispersion of the LAN access switches across many buildings in a larger campus facility would require more fiber-optic interconnects back to a single collapsed core
- When multiple distribution layers need to be interconnected, it becomes necessary to use a core layer, as illustrated in Figure 22-8.
T/F: GLBP only works on loop free topologies.
True.
Gateway Load Balancing Protocol (GLBP) 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 “Routed Access”?
Routed access is an alternative configuration in which Layer 3 is extended all the way to the access layer switches. In this design, access layer switches act as full Layer 3 routed nodes (providing both Layer 2 and Layer 3 switching), and the access-to-distribution Layer 2 uplink trunks are replaced with Layer 3 point-to-point routed links.
Consequently, the Layer 2/ Layer 3 demarcation point is moved from the distribution switch to the access switch, as illustrated in Figure 22-10.
Which of the following are true with regards to access-to-distribution block design?
- First-hop redundancy protocol is required: It needs the help of first-hop redundancy protocols such as HSRP and VRRP.
- STP required: Without STP loops are a problem.
- Increased uplink utilization: Both uplinks from access to distribution can be used, increasing the effective bandwidth available to the end users and endpoints connected to the access layer switches.
- Easier troubleshooting: It offers common end-to-end troubleshooting tools (such as ping and traceroute).
- Slower convergence: Due to the additional complexity convergence is slower, but the benefits outweigh this cost.
1, 2, and 5 are false.
The routed access-to-distribution block design has a number of advantages over the Layer 2 access layer design:
- No first-hop redundancy protocol required: It eliminates the need for first-hop redundancy protocols such as HSRP and VRRP.
- No STP required: Because there are no Layer 2 links to block, this design eliminates the need for STP.
- Increased uplink utilization: Both uplinks from access to distribution can be used, increasing the effective bandwidth available to the end users and endpoints connected to the access layer switches.
- Easier troubleshooting: It offers common end-to-end troubleshooting tools (such as ping and traceroute).
- Faster convergence: It uses fast-converging routing protocols such as Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF).
What is VSS?
Virtual Switching System
A VSS combines a pair of switches into a single network element. For example, a VSS in the distribution layer of the network interacts with the access and core networks as if it were a single switch. See Figure 4-2.
An access switch connects to both chassis of the VSS using one logical port channel. The VSS manages redundancy and load balancing on the port channel. This capability enables a loop-free Layer 2 network topology. The VSS also simplifies the Layer 3 network topology because the VSS reduces the number of routing peers in the network.
Figure 4-2 shows VSS in a Distribution Network.
VSS Active and VSS Standby Chassis
When you create or restart a VSS, the peer chassis negotiate their roles. One chassis becomes the VSS active chassis, and the other chassis becomes the VSS standby.
The VSS active chassis controls the VSS. It runs the Layer 2 and Layer 3 control protocols for the switching modules on both chassis. The VSS active chassis also provides management functions for the VSS, such as module online insertion and removal (OIR) and the console interface.
The VSS active and VSS standby chassis perform packet forwarding for ingress data traffic on their locally hosted interfaces. However, the VSS standby chassis sends all control traffic to the VSS active chassis for processing.
Virtual Switch Link
For the two chassis of the VSS to act as one network element, they need to share control information and data traffic.
The virtual switch link (VSL) is a special link that carries control and data traffic between the two chassis of a VSS. The VSL is implemented as an EtherChannel with up to eight links. The VSL gives control traffic higher priority than data traffic so that control messages are never discarded. Data traffic is load balanced among the VSL links by the EtherChannel load-balancing algorithm.
When you configure VSL all existing configurations are removed from the interface except for specific allowed commands. When you configure VSL, the system puts the interface into a restricted mode. When an interface is in restricted mode, only specific configuration commands can be configured on the interface.
What is StackWise?
Cisco StackWise and Stackwise Virtual are technologies offered by Cisco Systems that allows some models of Catalyst switches to operate as though they were one switch.
One switch from the stack will act as the master switch. The master switch will maintain the stack and allow you to configure and monitor the whole stack as though one via a single console. This allows for more efficient management and typically provides more bandwidth between individual switches than other uplink technology.
If one switch fails, the remaining switches will continue to operate by bypassing it. If the master switch fails, another switch in the stack will automatically take over as master. This feature means greater redundancy, as one switch’s failure will not bring about a failure of the entire stack.
As each switch contains the entire configuration for the stack, one of the benefits of this technology is the ability to replace a faulty switch (any—including master) with a new switch. The stack will configure the new switch on-the-fly to accommodate minimal downtime and reduce maintenance effort and errors.
Stackwise physically connects the switch stack using special stack interconnect cables, typically up to eight switches per stack. StackWise Virtual allows the virtual clustering of two chassis together into a single, logical entity without physical interconnect cables.
T/F: The simplified campus design relies on switch clustering such as a virtual switching system (VSS) and stacking technologies like StackWise.
True.
The simplified campus design relies on switch clustering such as a virtual switching system (VSS) and stacking technologies such as StackWise, in which multiple physical switches act as a single logical switch.
What is SD-Access?
SD-Access, the industry’s first intent-based networking solution for the enterprise, is built on the principles of the Cisco Digital Network Architecture (DNA). It is a combination of the campus fabric design and the Digital Network Architecture Center (Cisco DNA or DNAC).
SD-Access adds fabric capabilities to the enterprise network through automation using SD-Access technology, and it provides automated end-to-end segmentation to separate user, device, and application traffic without requiring a network redesign. With its fabric capabilities, SD-Access provides services such as host mobility and enhanced security in addition to the normal switching and routing capabilities. SD-Access is covered in detail in Chapter 23, “Fabric Technologies.”
