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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

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

ANDing: (Boolean and)

Computers use digital logic to interpret IP addresses
This logic is called a Boolean AND. It is the comparison of two bits to yield:

1 & 1 = 1
1 & 0 = 0
0 & 1 = 0
0 & 0 = 0

Any # ANDed with 0 is always 0
Any # ANDed with 1 is always the original #
The ANDing of an IP address & mask = network address
A subnet mask “masks” the host bits of an IP address
Routers and hosts use ANDing to determine networks
It is frequently necessary to be able to use ANDing
You will need to know how routers make routing decisions
Start with the IP address & mask above/below each other

10101100.00010000.00010100.00100011 172.16.24.35 (Host)
11111111.11111111.11111111.111 00000 255.255.255.224
——————————————————
10101100.00010000.00010100.00100000 172.16.23.32 (network address for
host /27)

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Tags: vlan, ip, wan, cisco, study, switch