CCNA Dynamic Routing

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5- DYNAMIC ROUTING
5.1 Dynamic Routing Protocols
5.2 Distance Vector Dynamic Routing / RIP and RIPng
5.3 Link State Dynamic Routing
5.4 Routing Table

5.1 Dynamic Routing Protocols

STATICROUTINGvs DYNAMICROUTING
STATIC ROUTING DYNAMIC ROUTING
• Manually configured routing
entry
• Must be manually updated if
topology changes
• Suitable for very small networks
• Less CPU usage
• May be fine to use to or from a
stub network
• Easy to implement
• Uses Routing Protocols that
dynamically discover network
destinations and how to get to
them
• Automatically updated if
topology changes
• Suitable for large networks
• Rapid convergence
• May require more CPU

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DYNAMICROUTINGPROTOCOLS
• Create and maintain data
structures (Neighbor table,
topology table etc.)
• Exchange messages ( Hello,
update etc. )
• Use algorithms to determine
best path to the distance (i.e.
DUAL for EIGRP )

HOWDYNAMICPROTOCOLSWORK?
• Router sends & receives routing
messages on its interfaces
• Router shares messages with other
routers using same protocol
• Routers exchange router information
each other
• If router detects a topology change,
advertises this to others

DYNAMICROUTINGPROTOCOLCLASSES
• IpV6 : RIPng , EIGRP for IPv6, OSPFv3, IS-IS for IPv6, MBGP

INTERIORvs EXTERIORROUTINGPROTOCOLS
AS 200AS 100
IGP : In same AS (i.e. RIP, OSPF etc.)
EGP : Between different AS number (i.e. BGP )

DISTANCEVECTORvs LINKSTATEPROTOCOLS
DISTANCE VECTOR
PROTOCOLS
LINK STATE PROTOCOLS
• Require that a router
inform its neighbors of
topology changes
periodically
• RIP(v1,v2) and EIGRP
• Have the complete map
of network topology
• Choose the best path
relying on topology table
• No neighbor dependency
• OSPF and IS-IS

CLASSFULvs CLASSLESSPROTOCOLS
CLASSFUL PROTOCOLS CLASSLESS PROTOCOLS
• Subnet mask is NOT sent
in routing updates
• Class A , B or C routing
• No CDR or VLSM
support
• RIPv1 and IGRP (old
form of EIGRP )
• Subnet mask is sent in
routing updates
• Classless routing
• CDR and VLSM support
• RIPv2, EIGRP, IS-IS,
OSPF

ROUTINGPROTOCOLSCOMPARISONCHART

5.2 Distance Vector Dynamic Routing / RIP and RIPng

DISTANCEVECTOROVERVIEW
• Routers send updates to their
neighbor so they only know
what their neighbor says
• Routers don’t know whole
topology details
• RIP and EIGRP

RIP
• Distance vector protocol
• Each router creates its routing
table based on information
exchanged between neighbors
• Routing updates are sent every
30 seconds as broadcast
(RIPv1) or multicast to
224.0.0.9 (RIPv2)

RIP(cont)
• Bellman Ford Algorithm for
metric calculation
• Uses hop count as metric
• Maximum hop count = 15

ESTABLISHINGRIPROUTINGTABLE
10.42.0.0 10.43.0.010.41.0.0 10.44.0.0
R1 R2 R3
Network Interface Hop
10.41.0.0 Fe 0/1 0
10.42.0.0 Fe 0/0 0
10.42.0.0 Fe 0/0 0
10.43.0.0 Fe 0/1 0
10.43.0.0 Fe 0/0 0
10.44.0.0 Fe 0/1 0
Fa 0/1 Fa 0/1 Fa 0/1Fa 0/0 Fa 0/0 Fa 0/0
• First all routers install directly connected networks to routing table

ESTABLISHINGRIPROUTINGTABLE(cont)
10.42.0.0 10.43.0.010.41.0.0 10.44.0.0
R1 R2 R3
10.41.0.0 Fa 0/1 0
10.42.0.0 Fa 0/0 0
10.43.0.0 Fa 0/0 1
10.42.0.0 Fa 0/0 0
10.43.0.0 Fa 0/1 0
10.41.0.0 Fa 0/0 1
10.44.0.0 Fa 0/1 1
10.43.0.0 Fa 0/0 0
10.44.0.0 Fa 0/1 0
10.42.0.0 Fa 0/0 1
Fa 0/1 Fa 0/1 Fa 0/1Fa 0/0 Fa 0/0 Fa 0/0
• Routes are exchanged between neighbors and routing tables begin to grow

ESTABLISHINGRIPROUTINGTABLE(cont)
10.42.0.0 10.43.0.010.41.0.0 10.44.0.0
R1 R2 R3
10.41.0.0 Fa 0/1 0
10.42.0.0 Fa 0/0 0
10.43.0.0 Fa 0/0 1
10.44.0.0 Fa 0/0 2
10.42.0.0 Fa 0/0 0
10.43.0.0 Fa 0/1 0
10.41.0.0 Fa 0/0 1
10.44.0.0 Fa 0/1 1
10.43.0.0 Fa 0/0 0
10.44.0.0 Fa 0/1 0
10.42.0.0 Fa 0/0 1
10.41.1.0 Fa 0/0 2
Fa 0/1 Fa 0/1 Fa 0/1Fa 0/0 Fa 0/0 Fa 0/0
• After all routes are exchanged, full routing table is established

RIPCONFIGURATION
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3
Gig 0/1 Gig 0/1 Gig 0/1Gig 0/0 Gig 0/0 Gig 0/0

VERIFYINGRIPCONFIGURATION
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3

VERIFYINGRIPCONFIGURATION(cont)
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3

RIPng
• RIP Next Generation
• Supports IPv6 routing
• Max hop : 15

RIPngCONFIGURATION
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3
Gig 0/1
2001:DB8:CAFE:A001::1
Gig 0/0
2001:DB8:CAFE:A002::1
Gig 0/0
2001:DB8:CAFE:A001::2
Gig 0/1
2001:DB8:CAFE:A003::2
Gig 0/0
2001:DB8:CAFE:A003::3
Gig 0/1
2001:DB8:CAFE:A004::3

VERIFYINGRIPngCONFIGURATION
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3
Gig 0/1
2001:DB8:CAFE:A001::1
Gig 0/0
2001:DB8:CAFE:A002::1
Gig 0/0
2001:DB8:CAFE:A001::2
Gig 0/1
2001:DB8:CAFE:A003::2
Gig 0/0
2001:DB8:CAFE:A003::3
Gig 0/1
2001:DB8:CAFE:A004::3

VERIFYINGRIPngCONFIGURATION
10.42.0.0 10.43.0.0172.16.1.0 192.168.1.0
R1 R2 R3
Gig 0/1
2001:DB8:CAFE:A003::2
Gig 0/1
2001:DB8:CAFE:A004::3
Gig 0/0
2001:DB8:CAFE:A001::2
Gig 0/0
2001:DB8:CAFE:A003::3
Gig 0/1
2001:DB8:CAFE:A001::1
Gig 0/0
2001:DB8:CAFE:A002::1

5.3 Link State Routing

LINKSTATEROUTINGOVERVIEW
• Routers have the complete map
of network topology
• Routers choose the best path
relying on topology table
• No neighbor dependency
• OSPF and IS-IS
LINK STATE ROUTING

DJIKSTRAALGORITHM
• Shortest path from A to E is
through A-C-D-E (Cost=9)
• OSPF and IS-IS use this
shortest path algorithm to
determine the best path

LINKSTATEROUTINGOPERATION
1. Routers discover their directly connected neighbors and
send hello packets
2. Routers build Link State Packet (LSP) which has the link
state of directly connected links
3. LSPs are flooded to all neighbors and stored in a database
4. Database is used for constructing a full map of topology

LINKSTATEROUTINGOPERATION(HELLO)
R1
R2 R3
R1
R2 R3
10.41.28.0 10.41.28.0
10.41.29.0 10.41.29.0
10.41.30.0 10.41.30.0

LINKSTATEROUTINGOPERATION(LSP)
R1
R2 R3
10.41.28.0
10.41.29.0
10.41.30.0
LSP Ethernet Network R1 : 10.41.28.0 / Cost = 5
Serial Point To Point Link R1-R2 : 10.41.26.0 / Cost = 10
20
25

LINKSTATEROUTINGOPERATION(LSPFLOOD)
R1
R2 R3
10.41.28.0
10.41.29.0
10.41.30.0
LSP
5
LSP

BUILDINGLINKSTATEDATABASE
Ethernet Network R1 : 10.41.28.0 / Cost = 5
R1
LINK STATE DATABASE
• Finally each router establishes a link state database and calculates the best paths for the destination
networks. Best path results are added to routing table

5.4 Routing Table

ROUTINGTABLE
• Routing table is used to reach the best path for destination network
• ‘#show ip route’ for routers , ‘route print’ for end devices
• Directly connected networks appear automatically

ETHERNETOVERVIEW
IPv4ROUTERROUTINGTABLEENTRIES

ETHERNETOVERVIEW
ROUTINGTABLETERMS
• Ultimate Route
• Level-1 Route
• Level-1 Parent Route
• Level-2 Child Route

ETHERNETOVERVIEW
ULTIMATEROUTES
• A route that has an exit
interface or a next hop IP
address.
• Connected (C) , Local (L) and
dynamically learned routes
(R,D,O etc.) are ultimate routes

ETHERNETOVERVIEW
LEVEL-1PARENT/ LEVEL-2CHILDROUTE
• Level-1 Parent Route : Route that
has subnetted child routes.
Parent routes do not have an exit
interface or next hop IP address
• Level-2 Child Route : Subnetted
route, where the subnet mask is
greater than the classful subnet
mask (eg. /27 versus /24)
Level-1 Parent Route
Level-2 Child Route

CCNA Dynamic Routing

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