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Configuring a Web Interface:

Switches have web-based config tools that require an onboard HTTP server:
Web browser GUI.
Security Device Manager (SDM).
IP Phone and Telephony apps.
HTTP services ? security hole ? optional authentication.
If many users access HTTP services you may require a separate authentication server.
AAA and TACACS can be used to validate user credentials, (robust).
A less complex method allows use of the enable password.
A local authentication method requires the user to use a login username and password specified in the config.

S1(config)#ip http server ? turns on the server (on by default).
S1(config)#ip http authentication enable.

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Tags: wan, switch, cisco, router, vtp, study

Key Elements of Ethernet Networks:

CSMA/CD – Only used with half-duplex (hubs).
Full-duplex switches do not use CSMA/CD.
Ethernet signals are sent to every host in the LAN.

Carrier Sense:

All devices must listen before transmitting.
If signal detected (CS), wait before transmitting.
If no tfc detected, can transmit.
While transmitting – must listen for collisions.

Multi-access:

If 2 devices transmit at the same time = collision.

Collision Detection:

Other devices (not involved in collision), and transmitting devices, detect collision.

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Tags: study, vtp, 802.1q, guides, switch, cisco

Routing & Packet Forwarding

Routing Protocols & Concepts

Router as a Computer:

Computers that specialize in sending packets over the data network.
Responsible for interconnecting networks.
Routers are the network center.
Generally have a min of 2 connections:
WAN connection (Connection to ISP).
LAN connection.
In addition to packet forwarding, routers provide other services as well.
A router connects multiple networks.
This means that it has multiple interfaces that each belong to a different IP network.
Each network that a router connects to typically requires a separate interface.

Routing Table:

Used to determine the best path.
Incoming packets’ dest IP address is looked up in the table.
The table includes an exit interface or next hop.
Once a match is found, the router encapsulates the IP packet into the L2 frame of the exit interface.

Router as a computer:

Router components and their functions:
CPU – Executes OS instructions.
RAM – Contains the running copy of config, routing table, buffers, etc. Contents lost when pwr is off.
ROM – Holds diagnostic software used @ startup and the bootstrap prgm.
NVRAM – Stores startup config.
Flash – Contains the OS, non-volitile.
Interfaces – usually multiple physical interfaces. Examples of interface types:
Ethernet / Fast Ethernet interfaces.
Serial interfaces.
Management interfaces (concole).

Internetwork Operating System:

IOS
A multitasking OS integrated with routing, switching, internetworking, and telecomm functions.
Stored as an image. Many different IOS images available.
IOS interface is CLI
On boot, the startup-config file in NVRAM is copied into RAM and stored as the running-config file.
Changes entered by the admin are stored in the running-config and are immediately implemented by the IOS.

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Tags: switch, ip, 802.1q, guides, router, study

LAN Design:

The Hierarchical Network Model:

CCNA focuses on networks for SMBs (small, medium businesses).
A hierarchical design model is recommended.
Easier to manage and expand.
Problems are solved more quickly.

Hierarchical design divides the network into 3 layers.
Core, (CL).
Distribrution, (DL).
Access, (AL).

Each layer provides specific functions.
This “modularity” facilitates scalability and performance.

Access Layer, (AL): lowest

Interfaces with the end device (user).
Includes routers, switches, bridges, hubs and wireless APs.
Provides a means of connecting devices to the network and controlling which one communicate on the network.

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Tags: vlan, wan, ip, guides, vtp, switch