1. 1-LAN design 2-Scaling VALNs
Chapter 1 , 2

2. 1-LAN design
Chapter 1

3. The Need to Scale the Network
All enterprise networks must:
Support critical applications
Support converged network traffic
Support diverse business needs
Provide centralized administrative control

4. Hierarchical Design Model
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.
A hierarchical LAN design includes the following three layers, as shown in Figure:
Access layer: provides endpoints and users direct access to the network.
Distribution layer: assemble access layers and provides connectivity to services. 
Core layer: provides connectivity between distribution layers for large LAN environments. 

5. Hierarchical Design Model
Note:
User traffic is initiated at the access layer and passes through the other layers.
Some smaller enterprise networks may implement a two-tier hierarchical design. In a two-tier hierarchical design, the core and distribution layers are collapsed into one layer.

6. Design for Scalability
Recommendations:
Use expandable equipment or devices that can be easily upgraded to increase capabilities.
Design a hierarchical network: can be added, upgraded, and modified, as necessary, without affecting the design of the other functional areas of the network. 
Create an IPv4 or IPv6 address strategy that is hierarchical. 
Choose routers or multilayer switches to limit broadcasts and filter other undesirable traffic from the network. 

7. Design for Scalability
advanced network design requirements include:
Implementing redundant links.
Implementing multiple links between equipment.
Using a scalable routing protocol.
Implementing wireless connectivity

8. Planning for Redundancy
Redundancy is an important part of network design for preventing disruption of network services by minimizing the possibility of a single point of failure.
One method of implementing redundancy is by installing duplicate equipment.
Another method of implementing redundancy is redundant paths.
Note: redundant paths in a switched Ethernet network may cause logical Layer 2 loops. For this reason, Spanning Tree Protocol (STP) is required.

9. Failure Domains
Failure domain is the area of a network that is impacted when a critical device or network service experiences problems.
The function of the device that initially fails determines the impact of a failure domain. Example: router or switch.
It is easiest and usually least expensive to control the size of a failure domain in the distribution layer than core layer.

10. Increasing Bandwidth Implementing EtherChannel:
EtherChannel is a form of link aggregation used in switched networks.
link aggregation allows an administrator to increase the amount of bandwidth between devices by creating one logical link made up of several physical links.
EtherChannel uses the existing switch ports; therefore, additional costs to upgrade the link to a faster and more expensive connection are not necessary.

11. Increasing Bandwidth
Most configuration tasks are done on the EtherChannel interface, instead of on each individual port:
ensuring configuration consistency throughout the links.
load balancing between links.

12. Expanding the Access Layer
Implementing Wireless Connectivity:
Advantages:
increased flexibility, reduced costs, and the ability to grow and adapt to changing network and business requirements.
Requirements:
wireless NIC that incorporates a radio transmitter/receiver and the required software driver to make it operational.
a wireless router or a wireless access point (AP) .

13. Switch Platforms
There are five categories of switches for enterprise networks:
campus LAN Switches - To scale network performance in an enterprise LAN. Example: Cisco , 3560, 3650, 3850, 4500, 6500, and 6800 Series.
Cloud-Managed Switches - they monitor and configure thousands of switch ports over the web, without the intervention of onsite IT staff. Example: Cisco Meraki switches
Data Center Switches - promote infrastructure scalability, operational continuity, and transport flexibility. Example: the Cisco Nexus Series switches and the Cisco Catalyst Series switches.
Service Provider Switches - Service provider switches fall under two categories: aggregation switches and Ethernet access switches. 
Virtual Networking 

14. Switch Platforms

15. Switch Platforms Port Density
The port density of a switch refers to the number of ports available on a single switch. 
Forwarding Rates
Forwarding rates define the processing capabilities of a switch by rating how much data the switch can process per second. 
Power over Ethernet
PoE allows the switch to deliver power to a device over the existing Ethernet cabling. This feature can be used by IP phones and some wireless access points. 
PoE allows more flexibility when installing wireless access points and IP phones, allowing them to be installed anywhere that there is an Ethernet cable. 

16. Multilayer Switching
Multilayer switches are typically deployed in the core and distribution layers.
Multilayer switches are characterized by their ability to build a routing table, support a few routing protocols, and forward IP packets.

17. Router Functions
Connect multiple networks in an organization to provide interconnections among them.
Using the network portion of the destination IP address to determine the best path to send packets to their destination.
Provide broadcast containment
Connect remote locations
Group users logically by application or department
Provide enhanced security

18. Router Hardware Routers can be categorized as:
Fixed configuration: the desired router interfaces are built-in.
Modular: come with multiple slots that allow a network administrator to change the interfaces on the router.

19. Managing IOS Files and Licensing
When a Cisco IOS device is being selected or upgraded it is important to choose the proper IOS image with the correct feature set and version. 
In the image name: The version number and release number refer to the overall device operating system. The platform refers to the specific model of a device. The feature set determines what a particular device is capable of.

20. Basic Router Show Commands
The show startup-config command can be used to display the Cisco device configuration stored in NVRAM.
The show running-config command can be used to display the currently active configuration that is stored in RAM.
The show flash command displays the files (not file content) stored in the flash memory.
The show port-security address command displays all secure MAC addresses configured on all switch interfaces.
The show mac-address-table command displays all MAC addresses that the switch has learned, how those addresses were learned (dynamic/static), the port number, and the VLAN assigned to the port. ​

21. Basic Router Show Commands
The show vlan brief command displays the available VLANs and the ports assigned to each VLAN.
The show vlan summary command displays the count of all configured VLANs.​
The show ip protocols command displays information about the routing protocols that are configured, the networks the router is advertising, and the default administrative distance.
The show interfaces command displays interfaces with line (protocol) status, bandwidth, delay, reliability, encapsulation, duplex, and I/O statistics.
The show ip interfaces command displays interface information, including protocol status, the IP address, whether a helper address is configured, and whether an ACL is enabled on the interface.
The show protocols command displays information about the routed protocol that is enabled and the protocol status of interfaces. ​

22. In-Band versus Out-of-Band Management
Out-of-band management is used for initial configuration or when a network connection is unavailable. Configuration using out-of-band management requires:
Direct connection to console or AUX port
Terminal emulation client
In-band management is used to monitor and make configuration changes to a network device over a network connection. Configuration using in-band management requires:
At least one network interface on the device to be connected and operational
Telnet, SSH, HTTP, or HTTPS to access a Cisco device

23. 2-Scaling VALNs
Chapter 2

24. VTP Overview
VLAN trunking protocol (VTP) allows a network administrator to manage VLANs on a switch configured as a VTP server.
The VTP server distributes and synchronizes VLAN information over trunk links to VTP-enabled switches throughout the switched network.
This minimizes the problems caused by incorrect configurations and configuration inconsistencies when it done manually.

25. VTP Modes A switch can be configured in one of three VTP modes:
VTP Server
Advertises the VTP domain VLAN information to other VTP-enabled switches in the same VTP domain
Stores the VLAN information for the entire domain in NVRAM
Creates, deletes, or renames VLANs for the domain
Default VTP mode
VTP Client
Cannot create, change, or delete VLANs
Stores the VLAN information for the entire domain in RAM
Must be configured as VTP client
VTP Transparent
Does not participate in VTP except to forward VTP advertisements to VTP clients and VTP server
VLANs that are created, renamed, or deleted on transparent switches are local to that switch only
Must be configured as VTP transparent

26. VTP Advertisements VTP includes three types of advertisements:
Summary advertisements - These inform adjacent switches of VTP domain name and configuration revision number. By default, Cisco switches issue summary advertisements every five minutes.
Advertisement request - These are in response to a summary advertisement message when the summary advertisement contains a higher configuration revision number than the current value.
Subset advertisements - These contain VLAN information including any changes.

27. Configuration Revision Number
The configuration revision number is a 32-bit number that indicates the level of revision for a VTP packet. Each VTP device tracks the VTP configuration revision number that is assigned to it.
This information is used to determine whether the received information is more recent than the current version. Each time that you make a VLAN change in a VTP device, the configuration revision is incremented by one.
To reset a configuration revision on a switch, change the VTP domain name, and then change the name back to the original name.

28. VTP Domain Name
Name that identifies the administrative domain for the switch.
By default, the VTP domain name is NULL.

29. VTP Advertisements Operation:
When the switch receives a summary advertisement packet, the switch compares the VTP domain name to its own VTP domain name. If the name is different, the switch simply ignores the packet. If the name is the same, the switch then compares the configuration revision to its own revision.  If its own configuration revision number is lower, an advertisement request is sent asking for the subset advertisement message, otherwise ignore the packet. The subset advertisement message contains the VLAN information with any changes. 

30. VTP Configuration Overview
Step 1: Configure the VTP Server
S1(config)# vtp mode server
Step 2: Configure the VTP Domain Name and Password
S1(config)# vtp domain CCNA  S1(config)# vtp password 1234
Step 3: Configure the VTP Clients
S2(config)# vtp mode client
S2(config)# vtp domain CCNA  S2(config)# vtp password 1234
Step 4: Configure VLANs on the VTP Server
S1(config)# vlan 10  S1(config)# name [name]
Step 5: Verify the VTP Clients Have Received the New VLAN Information
S1# show vlan brief

31. Troubleshoot VTP Issues
Common problems with VTP are:
using a non-trunk link to connect switches
using non-Cisco switches
Incorrect VTP Domain Name

32. VLAN Ranges on Switches
Normal Range VLANs
Used in small- and medium-sized business and enterprise networks.
Identified by a VLAN ID between 1 and 1005.
IDs 1 and 1002 to 1005 are automatically created and cannot be removed.
Configurations are stored within a VLAN database file, called vlan.dat. The vlan.dat file is located in the flash memory of the switch.
The VLAN Trunking Protocol (VTP), which helps manage VLAN configurations between switches, can only learn and store normal range VLANs.

33. VLAN Ranges on Switches
Extended Range VLANs
Enable service providers to extend their infrastructure to a greater number of customers. Some global enterprises could be large enough to need extended range VLAN IDs.
Are identified by a VLAN ID between 1006 and 4094.
Configurations are not written to the vlan.dat file.
Support fewer VLAN features than normal range VLANs.
Are, by default, saved in the running configuration file.
VTP does not learn extended range VLANs.

34. Creating a VLAN

35. Assigning Ports to VLANs

36. Configuring Extended VLANs
In order to configure an extended VLAN on a switch it must be set to VTP transparent mode.
switch(config)# vtp mode transparent
switch(config)# vlan 2000

37. Dynamic Trunking Protocol (DTP)
An interface can be set to trunking or nontrunking, or to negotiate trunking with the neighbor interface. Trunk negotiation is managed by the (DTP).
DTP manages trunk negotiation only if the port on the neighbor switch is configured in a trunk mode that supports DTP.
DTP is Cisco proprietary and not usable by other vendors.
Cisco best practice recommends disabling DTP on links where trunking is not intended and when a Cisco switch is connected to a non-Cisco switch. DTP is required for dynamic trunk negotiation.

38. Negotiated Interface Modes
Ethernet interfaces on switches support different trunking modes with the help of DTP:
switchport mode access .
switchport mode dynamic auto 
switchport mode dynamic desirable 
switchport mode trunk 
To prevent DTP frames from being generated by the interface of a Cisco switch, use the S1(config-if)# switchport nonegotiate command.

39. Verify Switch Configuration
The show interfaces switchport command displays the following information for a given port:
Switchport
Administrative Mode
Operational Mode
Administrative Trunking Encapsulation
Operational Trunking Encapsulation
Negotiation of Trunking
Access Mode VLAN
Trunking Native Mode VLAN
Administrative Native VLAN tagging
Voice VLAN

40. Interface Issues
VLANs correspond to unique subnets on the network. For inter-VLAN routing to operate, a router must be connected to all VLANs, either by separate physical interfaces or by subinterfaces. 
When enabling inter-VLAN routing on a router, one of the most common configuration errors is to connect the physical router interface to the wrong switch port. it places the router interface in the incorrect VLAN and prevents it from reaching the other devices within the same subnet.
Switch ports after the VLAN to which they are assigned is deleted will stop communicating with the attached devices. The affected ports must be reconfigured for an active VLAN.
Each VLAN requires its own network number, broadcast address, and valid IP addresses because each VLAN is a separate network. IP addressing schemes are frequently designed with the VLAN numbers as part of the design.
Multilayer switches can perform inter-VLAN routing by the use of internal VLAN interfaces.