Hierarchical internetworking model

The Hierarchical internetworking model is a three-layer model for network design first proposed by Cisco. It divides enterprise networks into three layers: core, distribution, and access layer.

Access layer

End-stations and servers connect to the enterprise at the access layer. Access layer devices are usually commodity switching platforms, and may or may not provide layer 3 switching services. The traditional focus at the access layer is minimizing "cost-per-port": the amount of investment the enterprise must make for each provisioned Ethernet port. This layer is also called the desktop layer because it focuses on connecting client nodes, such as workstations to the network.

Distribution layer

The distribution layer is the smart layer in the three-layer model. Routing, filtering, and QoS policies are managed at the distribution layer. Distribution layer devices also often manage individual branch-office WAN connections. This layer is also called the Workgroup layer.

Core layer

The core network provides high-speed, highly redundant forwarding services to move packets between distribution-layer devices in different regions of the network. Core switches and routers are usually the most powerful, in terms of raw forwarding power, in the enterprise; core network devices manage the highest-speed connections, such as 10 Gigabit Ethernet.

Reference

Basic Concept

Cisco IOS Command Modes:

Command Mode	Access Method	Prompt
User EXEC	Log in.	Router>
Privileged EXEC	From user EXEC mode, use the enable EXEC command.	Router#
Global configuration	From privileged EXEC mode, use the configure terminal privileged EXEC command.	Router(config)#

Some basic Troubleshoot/Show Command for Router/Switch/ASA

Some basic Troubleshoot/Show Command for Router/Switch/ASA:

Basic Show command:

Router#show clock

Router#show version               >> System hardware and software status

Router#show hosts   >> IP domain-name, lookup style, nameservers, and host table

Router#show file systems        >> Device File Systems

Router#show flash:                  >> about flash: file system

Router#show running-config   >> Current operating configuration
Router#show startup-config               >> Startup configuration 
Router#copy running-config startup-config >>Save running to startup config
Router#write                                          >>Save running to startup config

Router#show arp                      >>  IP ARP table

Router#show cdp neighbors     >> CDP neighbor entries

Show Routing table:

Router#show ip route >> on router/switch

ASA#show route >> on ASA

NAT/PAT:

Router#show ip nat translations  >> Translation entries

VLAN Troubleshoot command:

Router#show vtp status                    >> VTP domain status

Router#show vlan-switch brief        >> VTP all VLAN status in brief

Router#show interfaces vlan  1         >> Catalyst Vlans

Router#show interfaces trunk           >> Show interface trunk information

Switch#vlan database    >> see vlan info

ACL:

Router#show access-lists 10     >> ACL number

Router#show access-lists abc   >> ACL name

How to assign IP address on Router/Switch/ASA

Some basic configuration for Router/Switch/ASA:

Assign IP Address:

Router>enable

Router#configure terminal

Router(config)#interface fastEthernet 0/0   >> Same as Serial Interface

Router(config-if)#ip address 172.16.100.1 255.255.255.0   >> IP Address

Router(config-if)#no shutdown   >> By default shutdown all interface so, you need to UP interface.

                               

Assign IP Address in Router/Switch:

Router#configure terminal

Router(config)#interface vlan 1  >> Create interface as your requirement (vlan 2, vlan 3)

Router(config-if)#ip address 172.16.200.2 255.255.255.0  >> as your requirement

Router(config-if)#no shutdown