IP Networks and Routing

gascitytankNetworking and Communications

Oct 28, 2013 (4 years and 8 months ago)


IP Networks and Routing

Oakton Community College

CIS 238

LINUX Network Setup







ethtool, sysctl (see sysctl.conf) ,

see ndd on non
LINUX systems


service network start/stop



/etc/sysctl.conf, sysctl.d



IP Addressing Requirements

Network address


Gateway address

Static or DHCP

IP addressing

IP addresses

Consist of 32 bits normally expressed either as
four binary octets separated by periods or as four
sets of decimal numbers separated by periods

Contain a network ID and a host ID defined by the
subnet mask

If more than local addressing must also supply a
Gateway address to the rest of the world.

IP Address Classes

Five different classes of IP addresses

First three reserve a certain portion of the 32 bits
available for the network ID and the host ID

Last two are used in special situations only

Subnet Masks

bit numbers used to determine the portion
of an IP address that represents the network
ID and the host ID

Place a 1 in bit positions that correspond to
network ID bits and a zero in bits that
represent host ID bits

The host can perform a logical AND function
to determine if a destination IP address is on a
local network or a remote network

IP Subnetting

Process of borrowing host bits to increase the
number of network bits

Allows administrators to better utilize IP
networks that are either assigned to them
from the Internet Assigned Numbers Authority
(IANA) public IP addresses or from the private
address space defined by RFC 1918:,,

Network Routing


Process of moving information along a path from a
source to a destination on a network or between

On an IP network:

Source and destinations are called hosts

Information is fragmented into packets that are
transferred between these hosts

Direct (Local) Routing

Direct Routing (ARP only). Local delivery is via
MAC Address contained in ARP table.

Indirect Routing

Source and destination

hosts are not on the

same network segment

Packets must pass

through a router,

a physical link

between two or

more networks

Indirect Routing

IP determines location of routers in one of two ways:

Consults a locally maintained routing table, a list of networks
the system knows about and the IP addresses of routers that
packets must pass through to get to those networks

Uses a default gateway (if network is not found on the static
routing table)

Either way, the designated router for the address is on the
local network and is

for like any local host.

A route consists of:

a) network address

b) subnet mask

c) next hop gateway address.



A physical device used to connect a number of
network segments

Can be dedicated pieces of hardware, or can be
computers with more than one network adapter
card, each connected to a different network

Static and Dynamic Routers

Static routers

Router to which routes must be added manually.

Provide an entry in the routing table for every
network on the internetwork

Configure each router with a default gateway

Note: every host on a IP network is a static router, if
only for itself.

Dynamic routers

Routers that automatically share their routing
information with other routers on the network using a
routing protocols such as RIP, OSPF, EIGRP or BGP

Routing Protocols

Standard language that lets dynamic routers exchange
routing information

Basic types:


Distance (RIP, BGP)


Link State(OSPF) Both (EIGRP)


Interior: RIP, OSPF, IGRP


Exterior: EGP, BGP, EIGRP

Link state protocols separate networks into areas with
common network information

Autonomous system

One set of networks and routers all under the same
administration or group

Route Debugging

arp (

ping / pathping

ipconfig /all, ifconfig

tracert, traceroute