Hacking Manual

IGRP stands for Interior Gateway Routing Protocol.

IGRP is a distance vector protocol, meaning that it decides that the best path is the closest path. IGRP sends regular updates to it’s neighbors but it doesn’t talk as much as RIP. IGRP updates every 90 seconds. Because RIP couldn’t handle long distance relationships IGRP was created as a replacement. IGRP’s Default hop count is 100 but it can be set up to 255 hops by the network administrator. Which is way further than RIP’s 16 hop maximum.

RIP also lacked more than one routing metric. IGRP uses Bandwidth, Delay, reliability, and load as it’s routing metrics.

IGRP is a Cisco proprietary protocol. Meaning it only talks to routers made by Cisco. Kinda like the preppy girls from high school who wouldn’t be caught dead talking to someone who wasn’t popular.

IGRP uses hold down timers prevent gossip. When a route is marked invalid hold down timers prevent router gossip from reinstating that route. So lets pretend we have a router named Map , so if Map doesn’t receive an update from a particular route with in a certain period of time, it calculates the next best way to get to the destination, then it sends that information to all of the other routers. Then those routers update everyone else. The failed route change gets spread by word of mouth so to speak. But what if a router that hadn’t gotten an update and spreads false information to a router that had gotten the update. When a route is marked invalid, hold down timers prevent router gossip from reinstating that router. IGRP also uses split horizons and poison reverse to prevent routing loops.

Uses AS Number for activation
Invalid Timer: 270 seconds or 3 times how often it updates.
Hold down Timer: 280 seconds or 10 seconds more than the invalid timer.
Flush timer: 670 seconds or 7 times how often it updates.

EIGRP stands for Enhanced Interior Gateway Routing Protocol. It is a classless hybrid routing protocol created as an enhanced version of IGRP.

Just like it’s predecessor EIGRP is a Cisco proprietary routing protocol that uses an AS number. It synchronizes routing tables between neighbors at startup, and then it sends specific updates only when topology changes occur.

EIGRP performs path selection by using DUAL(Diffusing Update Algorithm)

EIGRP Supports several protocols including IP, IPX, and Apple Talk. It stored it’s data in the ram for fast retrieval. The three databases it uses are:

The Neighbor table
The Topology table
The Routing table

EIGRP Uses RTP and Supports multiple AS numbers It’s administrative distance is Internal:90 and External:270

Routers Are Layer 3 Devices A.K.A. Network Layer Device.

Routers connect separated networks together
Routers perform packet switching from one network to another

Routers perform packet filtering and path selection. If different routes are learned from multiple routes the lowest administrative distance determines which route is chosen.

The router says: “What’s the best way I can deliver this data?”

Every router makes it’s routing decsions alone, based on the information it has in it’s own routing table.

Sometimes a router is referred to as a DTE Device.

Routers do not forward broadcasts

A Router connects to a switch with a straight through cable.
Routers examine the destination IP address of a packet.
They send that packet to the next router reffered to as the next hop.

Routers can connect networks that use different routing protocols.
Routers allow multiple users to share a single connection to the internet.
Routers create separate broadcast and collision domains.

So if a broadcast is sent on one segment of the network, the router will not forward it to the other segments on the network. This is done to reduce unnecessary traffic.

The Router IOS loading sequence is
1. Flash
2. TFTP
3. ROM

If no IOS is found the router will enter Rom Monitor Mode.

This is a tutorial on how to do a Basic router configuration.

Router> enable
Router# configure terminal
Router(config)# hostname HM
HM(config)# enable password youllneverguess
HM(config)# enable secret youllneverguess
HM(config)# line console 0
HM(config-line)# password youllneverguess
HM(config-line)# login
HM(config-line)# line vty 0 4
HM(config-line)# password youllneverguess
HM(config-line)# login
HM(config-line)# exit

How to Configure the serial Interface:
HM(config)# interface s0/2
HM(config-if)# ip address 172.17.0.1 255.255.0.0
HM(config-if)# clock rate 64000
HM(config-if)# no shutdown
HM(config-if)# exit
HM(config)#

How to configure the Fast Ethernet Interface:
HM(config)# interface fastethernet 0/0
HM(config-if)# ip address 172.16.0.1 255.255.0.0
HM(config-if)# no shutdown
HM(config-if)# exit