IP Networks and Routing

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IP Networks and Routing

Oakton Community College

CIS 238

LINUX Network Setup


Commands:



-

ip


-

ifconfig


-

ethtool, sysctl (see sysctl.conf) ,


see ndd on non
-
LINUX systems


-

service network start/stop


Datasets:


-

/etc/sysctl.conf, sysctl.d


-

/etc/sysconfig/network
-
scripts


IP Addressing Requirements


Network address


NetMask


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


32
-
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:
10.0.0.0/8, 172.16.0.0/12. 192.168.0.0/16,
169.254.0.0/16


Network Routing


Routing


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


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
ARP’ed

for like any local host.



A route consists of:


a) network address


b) subnet mask


c) next hop gateway address.


Routers


Routers


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
segment


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 (
-
a)


ping / pathping


ipconfig /all, ifconfig
-
a


tracert, traceroute


netstat

rn


route