ROUTING

It forwards packets from one network to another network. It choose the best path from the routing table. The best path selection is based on the type of routing we are using (static/dynamic).

Types of Routing:

- Static Routing

- Default Routing

- Dynamic Routing

Static Routing:

- Best path is configured manually by the Administrator

- Administrator should know / Mandatory need of Destination Network ID

- It is secure and fast

Disadvantages:

- Everything should be configured manually

- It is used only in small network

- Any (small) changes will effect complete network

Default Routing:

- It is used to route traffic for unknown destinations (eg., internet)

- It is also used at end locations

- It is the last preferred routing

- Default routes helps in reducing the size of routing table

Dynamic Routing:

Advantages of Dynamic over Static:

- No need of manual configuration (unlike static routing)

- Learns about other networks via advertisements (of directly connected networks)

- Automatically select the best route (builds routing table)

- Update the topology changes dynamically

- No need to know the destination networks

- Administrative work is reduced

- Applicable for large organizations

Types of Dynamic Routing Protocols,

- Distance Vector Protocol

- Link State Protocol

- Hybrid Protocol

Differences of Dynamic routing protocols,

Classfull Protocols:

- Classfull routing protocol do not carry the subnet mask information along with updates

- All devices in the network must use the same subnet mask (FLSM or default same class)

Classless Protocols:

- Classless routing protocol carry the subnet mask information along with updates

- That is why it supports sub networks (VLSM and FLSM) and even default network as well

Routing Information Protocol:

- Open standard protocol (Cisco / Non-Cisco)

- Classfull routing protocol (does not carry subnet mask)

- Any Updates which will broadcasted via 255.255.255.255

- Metric: Hop count

- Load Balancing up to 4 equal paths

- Max Hop counts = 15 / Max routers = 16

- Applicable for small organizations

- Administrative distance is 120

- Exchange entire routing table for every 30 seconds (periodic updates)

Routing Protocol Classification:

IGP:

- Interior Gateway Protocol

- It is used to communicate within same autonomous system

- RIP, IGRP, EIGRP, OSPF, IS-IS

EGP:

- Exterior Gateway Protocol

- It is used to communicate between two or more autonomous system

- Border Gateway Protocol

Administrative Distance:

- Trust worthiness of the information received by the router

- The number is between 0 and 255

- Less AD value is more preferred routing

Autonomous System Number:

- It is a collection of networks under a common administrative domain

- A unique number identifying the routing domain of the routers (one organization)

- Ranges from 1 – 65535

Private Autonomous System:

- Used with in the same service provider

- Unique with in service provider

- Range between 64513 – 65535

Public Autonomous System:

- Used between multiple service provider

- Globally unique

- Range between 1 – 64512

“All credits regarding networking topics goes to NOA Solutions. If any one is interested recommending to start with NOA solutions.”

SUBNETTING

Subnetting is the process of Dividing a single network into multiple smaller network. It helps in minimizing the wastage of IP Address.

Subnetting can be performing in two ways,

FLSM(Fixed Length Subnet Mask) – where we divide the network into equal sizes.
VLSM(Variable Length Subnet Mask) – where we divide the network maybe equal or maynot be equal.

Subnetting can be done based on requirement,

Requirement of Hosts? (2)h-2 >= requirement
Requirement of Networks? (2)n >= requirement
Subnets? 2^n; n is a converted network bits from host bits
H = Host Bits N = Network Bits
What we do in subnetting,
Converting Host bits into Network Bits (reducing number of host bits), i.e., converting 0’s into 1’s

2power table which helps in creating of FLSM,

CISCO ROUTER

External Components of Router:

LAN interfaces

WAN interfaces

Administration interfaces

LAN Ports:

- Ethernet 10 Mbps

- Fast Ethernet 100 Mbps

- Gig Ethernet 1000 Mbps

- AUI(Attachment Unit Interface) (E0)-15 pin

Attachment Unit Interface:

- Commonly found on some old platform

- AUI pin configuration is 15 pin port (Ethernet LAN using 15pin instead of RJ45)

- Transceiver is used for converting 8 wires to 15 wires. i.e., RJ45 to 15 pin converter

WAN Ports:

- Serial Ports

- 60 pin or 26 pin smart serial

- ISDN interface (BRI) – RJ45 (used for ISDN wan connections)

Administration Ports:

Console Port:

- It is RJ45 Port

- Used for local administration, initial configuration, password recovery

Auxiliary Port:

- Its an RJ-45 port

- Used for remote administration

- Uses the console cable connecting to modem

Internal Components of Router:

ROM:

- Loads the bootstrap programs and searches for the IOS (Flash/TFTP/ROM)

FLASH:

- Stored IOS

NVRAM:

- Stores configuration (permanent)

- Startup-config

RAM:

- Stores configuration (temporary)

- Running-config

Booting process of Cisco Router:

POST – power on self-test checks the hardware

ROM – loads the bootstrap program and searches for the IOS

FLASH – stored IOS

NVRAM – stores configuration and startup configuration

RAM – stores configuration and running-config

 

Modes on Cisco Routers:

Setup Mode - If NVRAM is Blank

User Mode - Only some basic monitoring

Privileged Mode – monitoring and some troubleshooting

Global Configuration Mode – All configuration that effect the router globally

Interface Mode – Configurations done on the specific interface

Rommon Mode – Reverting password

Router Classification:
Fixed Router:
- All ports are integrated on motherboard(no slots)
- Non upgradable cannot add and remove the interfaces
- eg., 2500, 2800 router series

Modular Router:
- Have slots where we can add or remove cards
- Distribution and Core layer router is an example of modular router
- eg., 1600, 1700, 1800, 2600, 2800, 36