Unformatted text preview: 31 Days Before Your CCNP
and CCIE Enterprise Core
Exam
A Day-By-Day Review Guide
for the ENCOR 350-401
Certification Exam Patrick Gargano Cisco Press Contents
Day 31. Enterprise Network Architecture
Day 30. Packet Switching and Forwarding
Day 29. LAN Connectivity
Day 28. Spanning Tree Protocol
Day 27. Port Aggregation
Day 26. EIGRP
Day 25. OSPFv2
Day 24. Advanced OSPFv2 & OSPFv3
Day 23. BGP
Day 22. First-Hop Redundancy Protocols
Day 21. Network Services
Day 20. GRE and IPsec
Day 19. LISP and VXLAN
Day 18. SD-Access
Day 17. SD-WAN
Day 16. Multicast
Day 15. QoS
Day 14. Network Assurance (part 1)
Day 13. Network Assurance (part 2)
Day 12. Wireless Concepts
Day 11. Wireless Deployment
Day 10. Wireless Client Roaming and Authentication Day 9. Secure Network Access
Day 8. Infrastructrure Security
Day 7. Virtualization
Day 6. SDN and Cisco DNA Center
Day 5. Network Programmability
Day 4. Automation
Day 3. SPARE
Day 2. SPARE
Day 1. ENCOR Skills Review and Practice Table of Contents
Day 31. Enterprise Network Architecture
ENCOR 350-401 Exam Topics
Key Topics
Hierarchical LAN Design Model
Enterprise Network Architecture Options
Study Resources
Day 30. Packet Switching and Forwarding
ENCOR 350-401 Exam Topics
Key Topics
Layer 2 Switch Operation
Layer 3 Switch Operation
Forwarding Mechanisms
Study Resources
Day 29. LAN Connectivity
ENCOR 350-401 Exam Topics
Key Topics
VLAN Overview
Access Ports
802.1Q Trunk Ports
Dynamic Trunking Protocol
VLAN Trunking Protocol
Inter-VLAN Routing
Study Resources
Day 28. Spanning Tree Protocol
ENCOR 350-401 Exam Topics
Key Topics
IEEE 802.1D STP Overview Rapid Spanning Tree Protocol
STP and RSTP Configuration and Verification
STP Stability Mechanisms
Multiple Spanning Tree Protocol
Study Resources
Day 27. Port Aggregation
ENCOR 350-401 Exam Topics
Key Topics
Need for EtherChannel
EtherChannel Mode Interactions
EtherChannel Configuration Guidelines
EtherChannel Load Balancing Options
EtherChannel Configuration and Verification
Advanced EtherChannel Tuning
Study Resources
Day 26. EIGRP
ENCOR 350-401 Exam Topics
Key Topics
EIGRP Features
EIGRP Reliable Transport Protocol
Establishing EIGRP Neighbor Adjacency
EIGRP Metrics
EIGRP Path Selection
EIGRP Load Balancing and Sharing
Study Resources
Day 25. OSPFv2
ENCOR 350-401 Exam Topics
Key Topics
OSPF Characteristics
OSPF Process OSPF Neighbor Adjacencies
Building a Link-State Database
OSPF Neighbor States
OSPF Packet Types
OSPF LSA Types
Single-Area and Multiarea OSPF
OSPF Area Structure
OSPF Network Types
OSPF DR and BDR Election
OSPF Timers
Multiarea OSPF Configuration
Verifying OSPF Functionality
Study Resources
Day 24. Advanced OSPFv2 & OSPFv3
ENCOR 350-401 Exam Topics
Key Topics
OSPF Cost
OSPF Passive Interfaces
OSPF Default Routing
OSPF Route Summarization
OSPF Route Filtering Tools
OSPFv3
OSPFv3 Configuration
Study Resources
Day 23. BGP
ENCOR 350-401 Exam Topics
Key Topics
BGP Interdomain Routing
BGP Multihoming
BGP Operations BGP Neighbor States
BGP Neighbor Relationships
BGP Path Selection
BGP Path Attributes
BGP Configuration
Study Resources
Day 22. First-Hop Redundancy Protocols
ENCOR 350-401 Exam Topics
Key Topics
Default Gateway Redundancy
First Hop Redundancy Protocol
HSRP
VRRP
Study Resources
Day 21. Network Services
ENCOR 350-401 Exam Topics
Key Topics
Network Address Translation
Network Time Protocol
Study Resources
Day 20. GRE and IPsec
ENCOR 350-401 Exam Topics
Key Topics
Generic Routing Encapsulation
IP Security (IPsec)
Study Resources
Day 19. LISP and VXLAN
ENCOR 350-401 Exam Topics
Key Topics
Locator/ID Separation Protocol Virtual Extensible LAN (VXLAN)
Study Resources
Day 18. SD-Access
ENCOR 350-401 Exam Topics
Key Topics
Software-Defined Access
Study Resources
Day 17. SD-WAN
ENCOR 350-401 Exam Topics
Key Topics
Software-Defined WAN
Study Resources
Day 16. Multicast
ENCOR 350-401 Exam Topics
Key Topics
Multicast Overview
Study Resources
Day 15. QoS
ENCOR 350-401 Exam Topics
Key Topics
Quality of Service
Study Resources
Day 14. Network Assurance (part 1)
ENCOR 350-401 Exam Topics
Key Topics
Troubleshooting Concepts
Network Diagnostic Tools
Cisco IOS IP SLAs
Switched Port Analyzer Overview Study Resources
Day 13. Network Assurance (part 2)
ENCOR 350-401 Exam Topics
Key Topics
Logging Services
Study Resources
Day 12. Wireless Concepts
ENCOR 350-401 Exam Topics
Key Topics
Explain RF Principles
Study Resources
Day 11. Wireless Deployment
Day 10. Wireless Client Roaming and Authentication
Day 9. Secure Network Access
Day 8. Infrastructrure Security
Day 7. Virtualization
Day 6. SDN and Cisco DNA Center
Day 5. Network Programmability
Day 4. Automation
Day 3. SPARE
Day 2. SPARE
Day 1. ENCOR Skills Review and Practice Day 31. Enterprise Network Architecture ENCOR 350-401 EXAM TOPICS
Explain the different design principles used in an
enterprise network
• Enterprise network design such as Tier 2, Tier
3, and Fabric Capacity planning KEY TOPICS
Today we review the hierarchical LAN design model, as
well as the options available for different campus
network deployments. This is a high-level overview of the
enterprise campus architectures that can be used to scale
from a small corporate network environment to a large
campus-sized network. We will look at design options
such as:
Two-tier design (collapsed core)
Three-tier design
Layer 2 access layer (STP based) – loop-free and
looped
Layer 3 access layer (routed based)
Simplified campus design using VSS and StackWise
Software-Defined Access (SD-Access) Design
Spine-and-leaf architecture HIERARCHICAL LAN DESIGN MODEL
The campus LAN uses a hierarchical design model to
break the design up into modular groups or layers.
Breaking the design up into layers allows each layer to
implement specific functions, which simplifies the network design and therefore the deployment and
management of the network.
In flat or meshed network architectures, even small
configuration changes tend to affect many systems.
Hierarchical design helps constrain operational changes
to a subset of the network, which makes it easy to
manage as well as improve resiliency. Modular
structuring of the network into small, easy-tounderstand elements also facilitates resiliency via
improved fault isolation.
A hierarchical LAN design includes the following three
layers:
Access layer - Provides endpoints and users direct
access to the network.
Distribution layer - Aggregates access layers and
provides connectivity to services.
Core layer - Provides backbone connectivity
between distribution layers for large LAN
environments, as well as connectivity to other
networks within or outside the organization.
Figure 31-1 illustrates a hierarchical LAN design using
three layers. Figure 31-1 Hierarchical LAN Design Access Layer
The access layer is where user-controlled devices, useraccessible devices, and other end-point devices are
connected to the network. The access layer provides both
wired and wireless connectivity and contains features
and services that ensure security and resiliency for the
entire network. The access layer provides highbandwidth device connectivity, as well as a set of
network services that support advanced technologies,
such as voice and video. The access layer is one of the
most feature-rich parts of the campus network since it
provides a security, QoS, and policy trust boundary. It
offers support for technologies like Power over Ethernet
(PoE) and Cisco Discovery Protocol (CDP) for
deployment of wireless access points (APs) and IP
phones. Figure 31-2 illustrates the connectivity at the
access layer. Figure 31-2 Access Layer Connectivity Distribution Layer
In a network where connectivity needs to traverse the
LAN end-to-end, whether between different access layer
devices or from an access layer device to the WAN, the
distribution layer facilitates this connectivity. This layer
provides scalability and resilience as it is used to logically
aggregate the uplinks of access switches to one or more
distribution switches. Scalability is accomplished via the
aggregation of those access switches, while the resilience
is accomplished because of the logical separation with multiple distribution switches. The distribution layer is
the place where routing and packet manipulation are
performed, and this layer can be a routing boundary
between the access and core layers where QoS and load
balancing are implemented.
Figure 31-3 illustrates the connectivity at the distribution
layer. Figure 31-3 Distribution Layer Connectivity Core Layer
The core layer is the high-speed backbone for campus
connectivity, and it is the aggregation point for the other
layers and modules in the hierarchical network
architecture. It is designed to switch packets with
minimal processing as fast as possible 24x7x365. The
core must provide a high level of stability, redundancy,
and scalability. In environments where the campus is
contained within a single building—or multiple adjacent
buildings with the appropriate amount of fiber—it is
possible to collapse the core into distribution switches.
Without a core layer, the distribution layer switches will
need to be fully meshed. This design is difficult to scale
and increases the cabling requirements because each
new building distribution switch needs full-mesh
connectivity to all the distribution switches. The routing complexity of a full-mesh design increases as you add
new neighbors.
Figure 31-4 illustrates a network with and without a core
layer. The core layer reduces the network complexity,
from N * (N-1) to N links for N distributions (if using link
aggregation to the core, as shown in Figure 31-4),
otherwise it would N * 2 if using individual links to a
redundant core. Figure 31-4 LAN Topology With and Without a Core
Layer ENTERPRISE NETWORK
ARCHITECTURE OPTIONS
There are multiple enterprise network architecture
design options available for deploying a campus network,
depending on the size of the campus as well as the
reliability, resiliency, availability, performance, security,
and scalability required for it. Each possible option
should be evaluated against business requirements.
Since campus networks are modular, an enterprise
network could have a mixture of these options. Two-Tier Design (Collapsed Core)
The distribution layer provides connectivity to networkbased services, to the data center/server room, to the
WAN, and to the Internet edge. Network-based services
can include but are not limited to Cisco Identity Services
Engine (ISE) and wireless LAN controllers (WLC).
Depending on the size of the LAN, these services and the interconnection to the WAN and Internet edge may
reside on a distribution layer switch that also aggregates
the LAN access-layer connectivity. This is also referred to
as a collapsed core design because the distribution serves
as the Layer 3 aggregation layer for all devices.
It is important to consider that in any campus design
even those that can physically be built with a collapsed
core that the primary purpose of the core is to provide
fault isolation and backbone connectivity. Isolating the
distribution and core into two separate modules creates a
clean delineation for change control between activities
affecting end stations (laptops, phones, and printers) and
those that affect the data center, WAN or other parts of
the network. A core layer also provides for flexibility for
adapting the campus design to meet physical cabling and
geographical challenges.
In Figure 31-5, illustrates a collapsed LAN core. Figure 31-5 Two-Tier Design: Distribution Layer
Functioning as a Collapsed Core Three-Tier Design
Larger LAN designs require a dedicated distribution
layer for network-based services versus sharing connectivity with access layer devices. As the density of
WAN routers, Internet edge devices, and WLAN
controllers grows, the ability to connect to a single
distribution layer switch becomes hard to manage. When
connecting at least three distributions together, using a
core layer for distribution connectivity should be a
consideration.
The three-tier campus network is mostly deployed in
environments where multiple offices and buildings are
located closely together, allowing for high-speed fiber
connections to the headquarters owned by the
enterprise. Examples could be the campus network at a
university, a hospital with multiple buildings, or a large
enterprise with multiple buildings on a privately-owned
campus. Figure 31-6 illustrates a typical three-tier
campus network design. Figure 31-6 Three-Tier Design for Large Campus
Network Layer 2 Access Layer (STP Based) – LoopFree and Looped
In the traditional hierarchical campus design,
distribution blocks use a combination of Layer 2, Layer
3, and Layer 4 protocols and services to provide for
optimal convergence, scalability, security, and
manageability. In the most common distribution block
configurations, the access switch is configured as a Layer
2 switch that forwards traffic on high-speed trunk ports
to the distribution switches. Distribution switches are
configured to support both Layer 2 switching on their downstream access switch trunks and Layer 3 switching
on their upstream ports towards the core of the network.
With traditional layer 2 access layer design, there is no
true load balancing because STP blocks redundant links.
Load balancing can be achieved through manipulation of
STP and FHRP (HSRP, VRRP) settings and having traffic
from different VLANs on different links. However,
manual STP and FHRP manipulation is not true load
balancing. Another way to achieve good load balancing is
by limiting VLANs on a single switch and employing
GLBP, but this design might get complex. Convergence
can also be an issue. Networks using RSTP will have
convergence times just below a second, but sub-second
convergence is only possible with good hierarchical
routing design and tuned FHRP settings and timers.
Figure 31-7 illustrates two Layer 2 access layer
topologies: loop-free and looped. A loop-free topology is
where a VLAN is constrained to a single switch and a
Layer 3 link is used between distribution layer switches
to break the STP loop, ensuring that there are no blocked
ports from the access layer to the distribution layer. A
looped topology is where a VLAN spans multiple access
switches. In this case, a Layer 2 trunk link is used
between distribution layer switches. This design causes
STP to block links which reduces the bandwidth from the
rest of the network and can cause slower network
convergence. Figure 31-7 Layer 2 Loop-Free and Looped Topologies Layer 3 Access Layer (Routed Based)
An alternative configuration to the traditional
distribution block model is one in which the access
switch acts as a full Layer 3 routing node. The access-todistribution Layer 2 uplink trunks are replaced with
Layer 3 point-to-point routed links. This means that the
Layer 2/3 demarcation is moved from the distribution
switch to the access switch. There is no need for FHRP
and every switch in the network participates in routing.
In both the traditional Layer 2 access layer and the Layer
3 routed access layer designs, each access switch is
configured with unique voice and data VLANs. In the
Layer 3 design, the default gateway and root bridge for
these VLANs is simply moved from the distribution
switch to the access switch. Addressing for all end
stations and for the default gateway remain the same.
VLAN and specific port configuration remains
unchanged on the access switch. Router interface
configuration, access lists, DHCP Helper, and any other
configuration for each VLAN remain identical. However,
they are now configured on the VLAN SVI defined on the
access switch, instead of on the distribution switches.
There are several notable configuration changes
associated with the move of the Layer 3 interface down to
the access switch. It is no longer necessary to configure a
FHRP virtual gateway address as the “router” interfaces,
because all the VLANs are now local.
Figure 31-8 illustrates the difference between the
traditional Layer 2 access layer design and the Layer 3
routed access layer design. Figure 31-8 Layer 2 Access Layer and Layer 3 Access
Layer Designs Simplified Campus Design Using VSS
and StackWise
An alternative that can handle Layer 2 access layer
requirements and avoid the complexity of the traditional
multilayer campus is called a simplified campus design.
This design uses multiple physical switches that act as a
single logical switch, using either virtual switching
system (VSS) or StackWise. One advantage of this design
is that STP dependence is minimized, and all uplinks
from the access layer to the distribution are active and
forwarding traffic. Even in the distributed VLAN design,
you eliminate spanning tree blocked links caused by
looped topologies. You can also reduce dependence on
spanning tree by using MultiChassis EtherChannel
(MEC) from the access layer with dual-homed uplinks.
This is a key characteristic of this design, and you can
load balance between both physical distribution switches
since the access layer see the VSS as a single switch.
There are several other advantages to the simplified
distribution layer design. You no longer need IP gateway
redundancy protocols such as HSRP, VRRP, and GLBP,
because the default IP gateway is now on a single logical
interface and resiliency is provided by the distribution
layer VSS switch. Also, the network will converge faster
now that it is not depending on spanning tree to unblock
links when a failure occurs, because MEC provides fast
sub-second failover between links in an uplink bundle
Figure 31-9 illustrates the deployment of both StackWise
and VSS technologies. In the top diagram, two access
layer switches have been united into a single logical unit
by using special stack interconnect cables that create a
bidirectional closed-loop path. This bidirectional path
acts as a switch fabric for all the connected switches.
When a break is detected in a cable, the traffic is immediately wrapped back across the remaining path to
continue forwarding. Also, in this scenario the
distribution layer switches are each configured with an
EtherChannel link to the stacked access layer switches.
This is possible because the two access layer switches are
viewed as one logical switch from the perspective of the
distribution layer. Figure 31-9 Simplified Campus Design with VSS and
StackWise In the bottom diagram, the two distribution layer
switches have been configured as a VSS pair using a
virtual switch link (VSL). The VSL is made up of up to
eight 10 Gigabit Ethernet connections that are bundled
into an EtherChannel. The VSL carries the control plane
communication between the two VSS members, as well
as regular user data traffic. Notice the use of MEC at the
access layer. This allows the access layer switch to
establish an EtherChannel to the two different physical
chassis of the VSS pair. These links can be either Layer 2
trunks or Layer 3 routed connections.
Keep in mind that it is possible to combine both
StackWise and VSS in the campus network. They are not
mutually exclusive. Stackwise is typically found at the access layer, whereas VSS is found at the distribution
and core layers. Common Access-Distribution
Interconnection Designs
To summarize, there are four common accessdistribution interconnection design options:
Layer 2 looped design: Uses Layer 2 switching
at the access layer and on the distribution switch
interconnect. This introduces a Layer 2 loop
between distribution switches and access switches.
STP blocks one of the uplinks from the access
switch to the distribution switches. The
reconvergence time in case of uplink failure
depends on STP and FHRP convergence times.
Layer 2 loop-free design: Uses Layer 2
switching at the access layer and Layer 3 on the
distribution switch interconnect. There are no
Layer 2 loops between the access switch and the
distribution switches. Both uplinks from the access
layer switch are forwarding. Reconvergence time, in
case of an uplink failure, depend...
View
Full Document