Switching and Routing Technique W.lilakiatsakun. Topics ► Review routing fundamental ► Routing Techniques Distance Vector – RIP V1,2 /IGRP /EIGRP

Switching and Switching and Routing TechniqueRouting Technique

W.lilakiatsakunW.lilakiatsakun

TopicsTopics

► Review routing fundamental Review routing fundamental ► Routing TechniquesRouting Techniques

Distance Vector – RIP V1,2 /IGRP /EIGRPDistance Vector – RIP V1,2 /IGRP /EIGRP Link state Protocol – OSPF ,IS-ISLink state Protocol – OSPF ,IS-IS Hierarchical –BGPv4 Hierarchical –BGPv4

► Review Switching OperationReview Switching Operation► Switching TechniquesSwitching Techniques

Spanning Tree ProtocolSpanning Tree Protocol VLAN and TrunkVLAN and Trunk

►Network DesignNetwork Design Case study – campus network designCase study – campus network design

Review Routing FundamentalReview Routing Fundamental

►VLSM VLSM ►Static & Dynamic Routing Static & Dynamic Routing ►Routing algorithm conceptRouting algorithm concept► RIP V1 /V2 RIP V1 /V2

VLSM VLSM

►Variable Length Subnet MaskVariable Length Subnet Mask►VLSM allows an organization to use VLSM allows an organization to use

more than one subnet mask within the more than one subnet mask within the same network address spacesame network address space

►VLSM implementation maximizes VLSM implementation maximizes address efficiency, and is often address efficiency, and is often referred to as subnetting a subnetreferred to as subnetting a subnet

►Main reason – addressing crisis Main reason – addressing crisis

Short-term solution Short-term solution of addressing crisisof addressing crisis

►Subnetting (1985)Subnetting (1985)►VLSM VLSM (1987)(1987)►Classless interdomain routing (1993)Classless interdomain routing (1993)►Private IP Private IP ►NAT (Network Address Translation) NAT (Network Address Translation)

/PAT (Port Address Translation)/PAT (Port Address Translation)

Classful routing protocolClassful routing protocol

►RIP V1 (Routing Information Protocol) RIP V1 (Routing Information Protocol) ► IGRP (Interior Gateway Routing IGRP (Interior Gateway Routing

Protocol)Protocol)►Routing table is considered by class of Routing table is considered by class of

IP addressIP address 192.168.10.X 192.168.10.X 192.168.10.0 192.168.10.0 172.10.X.X 172.10.X.X 172.10.0.0 172.10.0.0 10.X.X.X 10.X.X.X 10.0.0.0 10.0.0.0

Supporting protocolsSupporting protocols

►OSPFOSPF► Integrated IS-ISIntegrated IS-IS► EIGRPEIGRP► RIP V2RIP V2► Static RoutingStatic Routing► Subnet informationSubnet information will be exchanged as will be exchanged as

well as routing informationwell as routing information 172.16.10.0 /172.16.10.0 /255.255.255.0255.255.255.0 10.5.2.0 /10.5.2.0 /255.255.255.0 255.255.255.0

VLSM - exampleVLSM - example

Calculating VLSMCalculating VLSM

Subnet MaskSubnet Mask

► 255.255.255.252 - /30255.255.255.252 - /30► 255.255.255.248 - /29255.255.255.248 - /29► 255.255.255.240 - /28255.255.255.240 - /28► 255.255.255.224 - /27255.255.255.224 - /27► 255.255.255.192 - /26255.255.255.192 - /26

► 255.255.255.128 - /25255.255.255.128 - /25► 255.255.255.0 - /24255.255.255.0 - /24► 255.255.254.0 - /23255.255.254.0 - /23► 255.255.252.0 - /22255.255.252.0 - /22► 255.255.248.0 - /21255.255.248.0 - /21

Waste of Space (1/2)Waste of Space (1/2)

► All one subnet and all zero subnet can be All one subnet and all zero subnet can be used to reduce the waste of spaceused to reduce the waste of space

Waste of space (2/2)Waste of space (2/2)

Sub-subnetSub-subnet (1/2)(1/2)

Sub-subnetSub-subnet (2/2)(2/2)

Calculating VLSM (1/6)Calculating VLSM (1/6)






Problem 1- 192.168.10.0/24Problem 1- 192.168.10.0/24

Route Aggregation Route Aggregation

►The use of classless interdomain The use of classless interdomain routing (CIDR) and VLSM prevents routing (CIDR) and VLSM prevents address waste and promotes route address waste and promotes route aggregation, or summarizationaggregation, or summarization

►Aka. Route SummarizationAka. Route Summarization►Save routing table spaceSave routing table space

Route summarization (1/3)Route summarization (1/3)



Review Routing fundamentalReview Routing fundamental

► Routing is the process that a router uses to Routing is the process that a router uses to forward packets toward the destination forward packets toward the destination network. network.

► A router makes decisions based upon A router makes decisions based upon the the destination IP address of a packet.destination IP address of a packet.

► To make the correct decisions, routers must To make the correct decisions, routers must learn how to reach remote networks. learn how to reach remote networks.

►When routers use When routers use dynamic routingdynamic routing, this , this information is learned from other routers. information is learned from other routers.

►When When static routingstatic routing is used, a network is used, a network administrator configures information about administrator configures information about remote networks manuallyremote networks manually

Static RoutingStatic Routing► Since static routes are configured manually, net Since static routes are configured manually, net

work administrators must add and delete static work administrators must add and delete static routes to reflect any network topology changes. routes to reflect any network topology changes.

► In a large network, the manual maintenance of r In a large network, the manual maintenance of r outing tables could require a lot of administrativ outing tables could require a lot of administrativ

e time. e time.► Static routing is not as scalable as dynamic rout Static routing is not as scalable as dynamic rout

ing because of the extra administrative require ing because of the extra administrative require ments. ments.

► InIn large networks, static routes that are intende large networks, static routes that are intende d to accomplish a specific purpose d to accomplish a specific purpose

► They They are often configured in conjunction with a are often configured in conjunction with a dynamic routing protocol. dynamic routing protocol.

Static route operationStatic route operation

► Network administrator configures the r Network administrator configures the r oute oute

► Router installs the route in the routing t Router installs the route in the routing t able able

► The static route is used to route packet The static route is used to route packet s. s.

Static route - configurationStatic route - configuration

Default route (1/4)Default route (1/4)

► Default routes are used to route packets Default routes are used to route packets with destinations that do not match any with destinations that do not match any

of the other routes in the routing table. of the other routes in the routing table.► Routers are typically configured with a d Routers are typically configured with a d

- efault route for Internet bound traffic, si - efault route for Internet bound traffic, si nce it is often impractical and unnecess nce it is often impractical and unnecess ary to maintain routes to all networks in ary to maintain routes to all networks in the Internet. the Internet.

► A default route is actually a special stati A default route is actually a special stati c route that uses this format: c route that uses this format:


► ip route ip route 0.0.0.0 0.0.0.00.0.0.0 0.0.0.0 [ [ - -next hop ad- -next hop ad dress dress | | outgoing interface outgoing interface ] ]

► The The 0.0.0.00.0.0.0 mask, when logically ANDe mask, when logically ANDe d to the destination IP address of the pa d to the destination IP address of the pa

cket to be routed, will always yield the cket to be routed, will always yield the network network 0.0.0.00.0.0.0

► If the packet does not match a more sp If the packet does not match a more sp ecific route in the routing table, it will b ecific route in the routing table, it will b

e routed to the e routed to the 0.0.0.00.0.0.0 network. network.



Routing ProtocolRouting Protocol

► A routing protocol is the communication used b A routing protocol is the communication used b etween routers. etween routers.

► A routing protocol allows routers to share infor A routing protocol allows routers to share infor mation about networks and their proximity to e mation about networks and their proximity to e

ach other. Routers use this information to build ach other. Routers use this information to build and maintain routing tables. and maintain routing tables.

► Examples of routing protocols are as follows: Examples of routing protocols are as follows: Routing Information Protocol (RIP) Routing Information Protocol (RIP) Interior Gateway Routing Protocol (IGRP) Interior Gateway Routing Protocol (IGRP) Enhanced Interior Gateway Routing Protocol (EIGRP) Enhanced Interior Gateway Routing Protocol (EIGRP) Open Shortest Path First (OSPF) Open Shortest Path First (OSPF)

Routed ProtocolRouted Protocol

► A routed protocol is used to direct user t A routed protocol is used to direct user t raffic. raffic.

► A routed protocol provides enough infor A routed protocol provides enough infor mation in its network layer address to al mation in its network layer address to al

low a packet to be forwarded from one h low a packet to be forwarded from one h ost to another based on the addressing ost to another based on the addressing

scheme.scheme.► Examples of routed protocols are as foll Examples of routed protocols are as foll

ows:ows: Internet Protocol (IP) Internet Protocol (IP) Internetwork Packet Exchange (IPX) Internetwork Packet Exchange (IPX)

Routing and Routed ProtocolRouting and Routed Protocol

Autonomous SystemAutonomous System

► An AS is a collection of networks under a comm An AS is a collection of networks under a comm on administration that share a common routing on administration that share a common routing

strategy. strategy.► To the outside world, an AS is viewed as a singl To the outside world, an AS is viewed as a singl

e entity. e entity.► The AS may be run by one or more operators w The AS may be run by one or more operators w

hile it presents a consistent view of routing to t hile it presents a consistent view of routing to t he external world. he external world.

► The American Registry of Internet Numbers (A The American Registry of Internet Numbers (A RIN), a service provider, or an administrator as RIN), a service provider, or an administrator as signs a signs a 16-16- bit identification number to each AS. bit identification number to each AS.

► EIGRP /OSPF /BGP EIGRP /OSPF /BGP require unique AS require unique AS numbernumber

AS (Autonomous System)AS (Autonomous System)

Dynamic Routing (1/2)Dynamic Routing (1/2)

► The goal of a routing protocol is to build and m The goal of a routing protocol is to build and m aintain a routing table. aintain a routing table.

► This table contains the learned networks and a This table contains the learned networks and a ssociated ports for those networks. ssociated ports for those networks.

► Routers use routing protocols to manage infor Routers use routing protocols to manage infor mation received from other routers and its inte mation received from other routers and its inte rfaces, as well as manually configured routes. rfaces, as well as manually configured routes.

► The routing protocol learns all available routes, The routing protocol learns all available routes, places the best routes into the routing table, a places the best routes into the routing table, a

nd removes routes when they are no longer val nd removes routes when they are no longer val id. id.

► The router uses the information in the routing t The router uses the information in the routing t able to forward routed protocol packets. able to forward routed protocol packets.

Dynamic Routing (2/2)Dynamic Routing (2/2)

► When all routers in an internetwork ope When all routers in an internetwork ope rate with the same knowledge, the inte rate with the same knowledge, the inte

rnetwork is said to have rnetwork is said to have converged.converged. ► Fast convergence is desirable Fast convergence is desirable because because

it reduces the period of time in which ro it reduces the period of time in which ro uters would continue to make incorrect uters would continue to make incorrect

routing decisions routing decisions

Routing Protocol Routing Protocol

Class of routing protocol Class of routing protocol

► Most routing algorithms can be classified Most routing algorithms can be classified into one of two categories: into one of two categories:

Distance vector Distance vector - Link state- Link state

► The distance vector The distance vector routing approach de routing approach de termines the direction, or vector, and dis termines the direction, or vector, and dis

tance to any link in an internetwork. tance to any link in an internetwork.► -The link state -The link state approach recreates the ex approach recreates the ex

act topology of an entire internetwork. act topology of an entire internetwork.

Distance Vector Routing Distance Vector Routing

► The distance vector routing algorithm The distance vector routing algorithm pp asses periodic copies of a routing table asses periodic copies of a routing table

from router to router. from router to router.► These regular updates between routers These regular updates between routers

communicate topology changes. communicate topology changes.► The distance vector routing algorithm i The distance vector routing algorithm i

s also known as the s also known as the - Bellman Ford algori- Bellman Ford algorithmthm . .

Distance Vector Operation Distance Vector Operation (1/2)(1/2)

Distance Vector Operation Distance Vector Operation (2/2)(2/2)

► Each router receives a routing table from i Each router receives a routing table from i ts directly connected neighbor routers. ts directly connected neighbor routers.

► Router B receives information from Router Router B receives information from Router A. Router B adds a distance vector number A. Router B adds a distance vector number

, such as a number of hops. , such as a number of hops.► This number increases the distance vector This number increases the distance vector

. .► Then Router B passes this new routing tabl Then Router B passes this new routing tabl

e to its other neighbor, Router C. e to its other neighbor, Router C.► - - This same step by step process occurs in a - - This same step by step process occurs in a

ll directions between neighbor routers ll directions between neighbor routers

Distance Vector Network Distance Vector Network DiscoveryDiscovery

Routing Metric ComponentRouting Metric Component

Link State ProtocolLink State Protocol

► - The link state algorithm is also known a - The link state algorithm is also known a s Dijkstra's algorithm or as the shortest s Dijkstra's algorithm or as the shortest

path first (SPF) algorithm. path first (SPF) algorithm.► - The link state routing algorithm maintai - The link state routing algorithm maintai

ns a complex database of topology infor ns a complex database of topology infor mation mation

► It also maintain It also maintain full knowledge of dista full knowledge of dista nt routers and how they interconnect nt routers and how they interconnect

Link State ConceptLink State Concept

Link State ConceptLink State Concept

► - Link state advertisement (LSA)- Link state advertisement (LSA) - a s - a s mall packet of routing information that i mall packet of routing information that i

s sent between routers s sent between routers► Topological database Topological database - a collection of - a collection of

information gathered from LSAs information gathered from LSAs► SPF algorithm SPF algorithm - a calculation perform - a calculation perform

ed on the database that results in the S ed on the database that results in the S PF tree PF tree

► Routing table Routing table - a list of the known pat - a list of the known pat hs and interfaces hs and interfaces

Link state Network discoveryLink state Network discovery

Link State ConcernLink State Concern

Routing Protocols (1/3)Routing Protocols (1/3)

Routing Protocols (1/3)Routing Protocols (1/3)

►RIPRIP - a distance vector interior routing p - a distance vector interior routing p rotocol rotocol

► IGRPIGRP - the Cisco distance vector interior - the Cisco distance vector interior routing protocol routing protocol

►OSPFOSPF - - a link state interior routing proto - - a link state interior routing proto col col

►EIGRPEIGRP - the advanced Cisco distance ve - the advanced Cisco distance ve ctor interior routing protocol ctor interior routing protocol

►BGPBGP - a distance vector exterior routing - a distance vector exterior routing protocol protocol

RIP (v1)RIP (v1)

► RIP was originally specified in RFC RIP was originally specified in RFC 10581058► Its key characteristics include the followin Its key characteristics include the followin

g:g: It is a distance vector routing protocol. It is a distance vector routing protocol. Hop count is used as the metric for path selecti Hop count is used as the metric for path selecti

on. on. If the hop count is greater than If the hop count is greater than 1515 , the packet i , the packet i

s discarded. s discarded. Routing updates are broadcast every Routing updates are broadcast every 3030 secon secon

ds, by default. ds, by default.

IGRPIGRP

► IGRP is a proprietary protocol develope IGRP is a proprietary protocol develope d by Cisco. d by Cisco.

► Some of the IGRP key design characteri Some of the IGRP key design characteri stics are as follows: stics are as follows:

It is a distance vector routing protocol. It is a distance vector routing protocol. Bandwidth, load, delay and reliability are u Bandwidth, load, delay and reliability are u

sed to create a composite metric. sed to create a composite metric. Routing updates are broadcast every Routing updates are broadcast every 9090 se se

conds, by default. conds, by default.

OSPFOSPF► - OSPF is a nonproprietary link state routing - OSPF is a nonproprietary link state routing

protocol. protocol. - It is a link state routing protocol. - It is a link state routing protocol. It is an open standard routing protocol describ It is an open standard routing protocol describ

ed in RFC ed in RFC 23282328 . . The SPF algorithm is used to calculate the low The SPF algorithm is used to calculate the low

est cost to a destination. est cost to a destination. Routing updates are flooded as topology chan Routing updates are flooded as topology chan

ges occur. ges occur.

EIGRPEIGRP

► EIGRP is a Cisco proprietary enhanced di EIGRP is a Cisco proprietary enhanced di stance vector routing protocol. stance vector routing protocol.

► The key characteristics of EIGRP are as f The key characteristics of EIGRP are as f ollows: ollows:

It is an enhanced distance vector routing pro It is an enhanced distance vector routing pro tocol. tocol.

It uses a combination of distance vector and It uses a combination of distance vector and- link state features.- link state features.

It uses Diffusing Update Algorithm (DUAL) to It uses Diffusing Update Algorithm (DUAL) to calculate the shortest path. calculate the shortest path.

Routing updates are multicast using Routing updates are multicast using224.0.0.10224.0.0.10 triggered by topology changes. triggered by topology changes.

BGPBGP

► Border Gateway Protocol (BGP) is an exter Border Gateway Protocol (BGP) is an exter ior routing protocol. ior routing protocol.

► The key characteristics of BGP are as follo The key characteristics of BGP are as follows:ws: It is a distance vector exterior routing protoco It is a distance vector exterior routing protoco

l. l. It is used between ISPs or ISPs and clients. It is used between ISPs or ISPs and clients. It is used to route Internet traffic between aut It is used to route Internet traffic between aut

onomous systems onomous systems Policy based concept rather than Policy based concept rather than

performance based conceptperformance based concept

IGP and EGPIGP and EGP

Distance Vector problemDistance Vector problem(Routing Loop)(Routing Loop)

Routing Loop (1/3)Routing Loop (1/3)►Before Network1 fails, Before Network1 fails, Router C, the pref Router C, the pref

erred path to Network erred path to Network11 is by way of Rout is by way of Rout er B, and the distance from Router C to N er B, and the distance from Router C to N

etwork etwork11 is is33 . .► When Network When Network11 fails, Router E sends an fails, Router E sends an

update to Router A. Router A stops routin update to Router A. Router A stops routin g packets to Network g packets to Network11 , but Routers B, C, , but Routers B, C,

and D continue to do so because they ha and D continue to do so because they ha ve not yet been informed of the failure. ve not yet been informed of the failure.

► When Router A sends out its update, Rou When Router A sends out its update, Rou ters B and D stop routing to Network ters B and D stop routing to Network11 . .

Routing Loop (2/3)Routing Loop (2/3)

► However, Router C has not received an u However, Router C has not received an u pdate. For Router C, Network pdate. For Router C, Network11 can still b can still b

e reached through Router B. e reached through Router B.► Now Router C sends a periodic update to Now Router C sends a periodic update to

Router D, which indicates a path to Netw Router D, which indicates a path to Netw ork ork11 by way of Router B. by way of Router B.

► Router D changes its routing table to refl Router D changes its routing table to refl ect this incorrect information, and sends ect this incorrect information, and sends the information to Router A. the information to Router A.

Routing Loop (3/3)Routing Loop (3/3)

►RR outer A sends the information to Rout outer A sends the information to Rout ers B and E, and the process continues. ers B and E, and the process continues.

► Any packet destined for Network Any packet destined for Network11 will will now loop from Router C to B to A to D a now loop from Router C to B to A to D a

nd back to again to C. nd back to again to C.►This condition is called This condition is called count to infinitycount to infinity

Count to InfinityCount to Infinity

Defining a maximumDefining a maximum

Split Horizon (1/2)Split Horizon (1/2)

Split HorizonSplit Horizon (2/2)(2/2)

► Split horizon is used to avoid Split horizon is used to avoid routing routing looploop..

► If a routing update about Network If a routing update about Network11 arr arr ives from Router A, Router B or Router ives from Router A, Router B or Router

D cannot send information about Netw D cannot send information about Netw ork ork11 back to Router A back to Router A

Route PoisoningRoute Poisoning

► Route poisoning is a method of quickly removi Route poisoning is a method of quickly removi ng outdated routing information from other ro ng outdated routing information from other ro

uter's routing tables uter's routing tables► It setsIt sets hop count to be unreachable (higher tha hop count to be unreachable (higher tha

n the maximum number of hops allowed) and s n the maximum number of hops allowed) and s ending a routing update. ending a routing update.

► When a router receives a route poisoning, it se When a router receives a route poisoning, it se nds an update back to the router from which it nds an update back to the router from which it

received the route poisoning, received the route poisoning,► TT his is called his is called poison reverse poison reverse . to ensure that all . to ensure that all

routers on a segment have received the poison routers on a segment have received the poison ed route information ed route information

Triggered update (1/2)Triggered update (1/2)

► Triggered updates do not wait for updat Triggered updates do not wait for updat e timers to expire. e timers to expire.

► They are sent when routing information They are sent when routing information has changed. has changed.

► A router will immediately send a routing A router will immediately send a routing update on its other interfaces update on its other interfaces

► Triggered updates, used in conjunction Triggered updates, used in conjunction with route poisoning, ensure that all rou with route poisoning, ensure that all rou ters know of failed routes before any ho ters know of failed routes before any ho

lddown timers can expire lddown timers can expire

Triggered update (2/2)Triggered update (2/2)

Holddown Timer (1/3)Holddown Timer (1/3)

Holddown Timer (2/3XHolddown Timer (2/3X

►After receiving updates that network is After receiving updates that network is unreachableunreachable TT he router marks the route as inaccessible a he router marks the route as inaccessible a

nd starts a holddown timer. nd starts a holddown timer.

► Before the holddown timer expires, Before the holddown timer expires, if an update is received from the same neigh if an update is received from the same neigh

bor, which indicates that the network is acce bor, which indicates that the network is acce ssible, ssible,

the router marks the network as accessible a the router marks the network as accessible a nd removes the holddown timer. nd removes the holddown timer.

Holddown Timer (3/3)Holddown Timer (3/3)

► If an update arrives from a different neighb If an update arrives from a different neighb or router with a better metric for the networ or router with a better metric for the networ k, the router marks the network as accessib k, the router marks the network as accessib le and removes the holddown timer le and removes the holddown timer

► If an update is received from a different rou If an update is received from a different rou ter with a higher metric before the holddow ter with a higher metric before the holddow

n timer expires, the update is ignored. n timer expires, the update is ignored. This update is ignored to allow more time for th This update is ignored to allow more time for th

e knowledge of a disruptive change to propagat e knowledge of a disruptive change to propagat e through the entire network. e through the entire network.

RIP - Routing ProcessRIP - Routing Process

► RIP has evolved over the years from a Cl RIP has evolved over the years from a Cl assful Routing Protocol, RIP v assful Routing Protocol, RIP v11 , to a Class , to a Class

less Routing Protocol, RIP v less Routing Protocol, RIP v22 . .► RIP v2 enhancements include the followi RIP v2 enhancements include the followi

ng:ng: Ability to carry additional packet routing info Ability to carry additional packet routing info

rmation rmation Authentication mechanism to secure table u Authentication mechanism to secure table u

pdates pdates - Support for variable length subnet mask (VL - Support for variable length subnet mask (VL

SM) SM)

RIP - Routing Process (2/2)RIP - Routing Process (2/2)

► To prevent indefinite routing loops, RIP i To prevent indefinite routing loops, RIP i mplements a limit on the number of hops mplements a limit on the number of hops

allowed in a path from a source to a desti allowed in a path from a source to a desti nation nation (15(15 hops)hops) . .

► When a router receives a routing update When a router receives a routing update that contains a new or changed entry, th that contains a new or changed entry, th

e metric value is increased by e metric value is increased by11 to accou to accou nt for itself as a hop in the path. nt for itself as a hop in the path.

► RIP implements split horizon and holddo RIP implements split horizon and holddo wn mechanisms to prevent the propagati wn mechanisms to prevent the propagati on of incorrect routing information. on of incorrect routing information.

RIP with Floating StaticRIP with Floating Static

RIP with Floating StaticRIP with Floating Static

► Each dynamic routing protocol has a def Each dynamic routing protocol has a def ault administrative distance (AD). ault administrative distance (AD).

► A static route can be defined as less desi A static route can be defined as less desi rable than a dynamically learned route, rable than a dynamically learned route,

as long as the AD of the static route is hi as long as the AD of the static route is hi gher than that of the dynamic route. gher than that of the dynamic route.

► To configure the floating static route, an To configure the floating static route, an AD of AD of 130130 was defined on the static rout was defined on the static rout

e. e.

AD (Administrative Distance)AD (Administrative Distance)

Documents

Switching and Routing Technique W.lilakiatsakun. Topics ► Review routing fundamental ► Routing Techniques Distance Vector – RIP V1,2 /IGRP /EIGRP