ROUTING PROTOCOLS (CCNA2)
1
Dr. Nawaporn Wisitpongphan
CCNA2:CHAPTER 2
USEFUL COMMANDS
2
CCNA2:CHAPTER 2
DETERMINING ROUTER INTERFACE
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CCNA2:CHAPTER 2
CISCO DISCOVERY PROTOCOL (CDP)
Proprietary tool that enables you to access a summary of
protocol and address information about Cisco devices that
are directly connected.
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CCNA2:CHAPTER 2
DIFFERENT TYPES OF ROUTES
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CCNA2:CHAPTER 2
DIRECTLY CONNECTED ROUTE (C)
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CCNA2:CHAPTER 2
CONFIGURING STATIC ROUTE
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CCNA2:CHAPTER 2
STATIC ROUTES (S)
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CCNA2:CHAPTER 2
RECURSIVE ROUTE LOOKUP
Exit Interface needs to be resolved before a packet can get forwarded.
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CCNA2:CHAPTER 2
CONFIG ROUTE WITH
EXIT INTERFACE
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CCNA2:CHAPTER 2
STATIC ROUTE SUMMARIZATION
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CCNA2:CHAPTER 2
DEFAULT ROUTE
R1(config)#ip route 0.0.0.0 0.0.0.0 serial 0/0/0
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CCNA2:CHAPTER 3
DYNAMIC ROUTING PROTOCOLS
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CCNA2:CHAPTER 3
DYNAMIC VS. STATIC ROUTING
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CCNA2:CHAPTER 3
METRIC FIELD IN ROUTING TABLE

RIP:
Cost = Hop count
 Best path is chosen with lowest hop count


IGRP and EIGRP:



Cost = Function(Bandwidth, Delay, Reliability, Load)
Best path is chosen by the route with smallest cost
IS-IS and OSPF


Cost = Function(Bandwidth)
Best path is chosen by the route with smallest cost
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CCNA2:CHAPTER 3
ADMINISTRATIVE DISTANCE (AD)
Administrative distance is an integer value from
0 to 255.
 The lower the value the more preferred the route
source.

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CCNA2:CHAPTER 3
METRIC VS. AD [AD/METRIC]
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CCNA2:CHAPTER 3
[AD/METRIC] OF DIRECTLY CONNECTED
ROUTE
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CCNA2:CHAPTER 4
DISTANCE VECTOR ROUTING PROTOCOLS

Routing Information Protocol (RIP)
Hop count is used as the metric for path selection.
 RIP cannot supply a route to a network with >15 hops
 Routing updates are broadcast every 30 seconds, by default


IGRP
Bandwidth, delay, load and reliability are used to create a
composite metric.
 Routing updates are broadcast every 90 seconds, by default.
 IGRP is the predecessor of EIGRP and is now obsolete.


EIGRP
It can perform unequal cost load balancing.
 It uses Diffusing Update Algorithm (DUAL) to calculate the
shortest path.
 No periodic update. Routing updates are sent only when there is19
a change in the topology.

CCNA2:CHAPTER 4
ROUTING PROTOCOL CHARACTERISTICS
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CCNA2:CHAPTER 4
RIP:
PERIODIC UPDATES & RIP TIMERS

Invalid Timer
If an update has not been received after 180 seconds (the
default), the route is marked as invalid by setting the
metric to 16.
 The route is retained in the routing table until the flush
timer expires.


Flush Timer



By default, the flush timer is set for 240 seconds.
When the flush timer expires, the route is removed from
the routing table.
Holddown Timer
Once a route is marked as unreachable, it must stay in
holddown long enough for all routers in the topology to
learn about the unreachable network.
 By default, the holddown timer is set for 180 seconds.
 Prevent routing loop. (CCNA2: 4.4.4)

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CCNA2:CHAPTER 4
RIP: TRIGGERED UPDATE

Triggered updates are sent when one of the
following occurs:
An interface changes state (up or down)
 A route has entered (or exited) the "unreachable"
state
 A route is installed in the routing table


Random Jitter

RIP uses RIP_JITTER to avoid update packet
collision
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CCNA2:CHAPTER 4
EIGRP
BOUNDED UPDATE
Non-periodic because they are not sent out on a
regular basis.
 Partial updates sent only when there is a change
in topology that influences routing information.
 Bounded, meaning the propagation of partial
updates are automatically bounded so that only
those routers that need the information are
updated.

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CCNA2:CHAPTER 5
RIPV1:
Classful routing protocol
 Do not send subnetmask in the update


Administrative Distance = 120
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Time since last update
CCNA2:CHAPTER 5
RIPV1: ENABLING RIP ON THE ROUTER
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CCNA2:CHAPTER 5
RIPV1:
ENABLES/DISABLE RIP ON INTERFACES
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CCNA2:CHAPTER 5
RIPV1:
BOUNDARY ROUTERS & AUTO SUMMARIZATION

RIP is a classful routing protocol that automatically summarizes
classful networks across major network boundaries.
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CCNA2:CHAPTER 5
RIPV1:DISADVANTAGE OF AUTO SUMMARIZATION
Discontiguous Topologies do not Converge with RIPv1
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CCNA2:CHAPTER 5
RIPV1: PROPAGATING DEFAULT ROUTE
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CCNA2:CHAPTER 6
CLASSLESS ROUTING PROTOCOLS
CIDR uses Variable Length Subnet Mask
(VLSM)
 RIPv2, EIGRP, OSPF, IS-IS, and BGP.

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CCNA2:CHAPTER 7
RIPV2: DIFFERENCES
RIPv1

A classful distance
vector routing protocol

Does not support
discontiguous subnets
RIPv2

A classless distance
vector routing protocol
that is an enhancement
of RIPv1’s features.

Next hop address is
included in updates
Routing updates are
multicast

Does not support VLSM

Does not send subnet
mask in routing update


Routing updates are
broadcast

The use of
authentication is an
option
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CCNA2:CHAPTER 7
RIPV2:
MESSAGE FORMAT
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CCNA2:CHAPTER 7
RIPV2:
ENABLING RIPV2
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CCNA2:CHAPTER 7
RIPV2:
HOW IT SOLVE DISCONTIGUOUS NETWORKS


By default, RIPv2 automatically summarizes networks at
major network boundaries, just like RIPv1.
Solution: “no auto-summary” on all routers
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CCNA2:CHAPTER 7
RIPV2: SOLVING DISCONTIGUOUS NETWORKS
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CCNA2:CHAPTER 7
RIPV2 SUPPORTS VLSM
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CCNA2:CHAPTER 7
RIPV2:
CIDR AND SUPERNET

Supernets have masks that are smaller than the
classful mask.

Example
R2(config)#ip route 192.168.0.0 255.255.0.0 Null0
 192.168.0.0 is in a class C address but we use /16 mask here

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CCNA2:CHAPTER 7
RIPV2:
VERIFICATION & TROUBLESHOOTING
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CCNA2:CHAPTER 8
ROUTING TABLE STRUCTURE

Level 1 Route
A level 1 route is a route with a subnet mask equal to or
less than the classful mask of the network address.
 Default route
 Supernet route
 Network route
 Ultimate Route: level-1 route with next-hop IP or exit
interface

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CCNA2:CHAPTER 8
LEVEL1 VS. LEVEL 2 ROUTE:
PARENT & CHILD ROUTES FOR CLASSFUL NETWORKS
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CCNA2:CHAPTER 8
PARENTS & CHILD ROUTES:
CLASSLESS NETWORKS
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 1
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 1A
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 1B
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 2
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 2A
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 2B
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 3
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 3A
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 3B
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 4
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CCNA2:CHAPTER 8
ROUTING TABLE LOOKUP: STEP 5
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CCNA2:CHAPTER 8
TABLE LOOKUP: LONGEST MATCH
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CCNA2:CHAPTER 8
CLASSFUL ROUTING BEHAVIOR
Destination IP = 172.16.4.0
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CCNA2:CHAPTER 8
CLASSLESS ROUTING BEHAVOIR
Destination IP = 172.16.4.0
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CCNA2:CHAPTER 8
IMPORTANT NOTE

Classful & Classless routing behavior is different from
classful/classless routing protocol
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CCNA2:CHAPTER 9
EIGRP
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CCNA2:CHAPTER 9
EIGRP PACKET TYPE: HELLO
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CCNA2:CHAPTER 9
EIGRP PACKET TYPE: UPDATE/ACK
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CCNA2:CHAPTER 9
EIGRP PACKET TYPE: QUERY & REPLY
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CCNA2:CHAPTER 9
DEFAULT HELLO INTERVAL & HOLD TIME


EIGRP routers discover neighbors and establish adjacencies with neighbor
routers using the Hello packet.
Hold time tells the router the maximum time the router should wait to
receive the next Hello before declaring that neighbor as unreachable.
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CCNA2:CHAPTER 9
EIGRP PARTIAL AND BOUNDED UPDATE
& DIFFUSING UPDATE ALGORITHM

DUAL: Diffusing Update Algorithm is used instead
of Bellman-Ford to speed up the convergence time.
Loop-Free
 Only routers affected by the change have to recompute
the routing table

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CCNA2:CHAPTER 9
EIGRP: AD
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CCNA2:CHAPTER 9
CONFIGURING EIGRP WITH AS ID
In order to establish neighbor adjacencies, EIGRP requires all routers in
the same routing domain to be configured with the same process ID
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NETWORK COMMAND WITH WILDCARD MASK
: SPECIFY CERTAIN INTERFACE ONLY
Wildcard = inverse of subnet mask
Router(config-router)#network network-address [wildcard-mask]
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CCNA2:CHAPTER 9
EIGRP NEIGHBOR TABLE
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CCNA2:CHAPTER 9
EIGRP COMPOSITE METRIC
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CCNA2:CHAPTER 9
EIGRP:
VERIFYING THE K VALUE
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CCNA2:CHAPTER 9
EIGRP: EXAMINING THE METRIC VALUE
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CCNA2:CHAPTER 9
EIGRP: DELAY VALUE
Delay is measure of the time taken to traverse
the link
 Delay is a static value based on the link type.

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CCNA2:CHAPTER 9
EIGRP: RELIABLITY & LOAD

Reliability







Probability that the link will fail
1 = not reliable
255 = very reliable
(255/255) = 100% reliable… 234/255 = 91.8% reliable
Calculated dynamically on 5 minute weighted
average
EIGRP do not use reliability in metric calculation!
Load
Amount of traffic utilizing the link
 Measured dynamically on 5 minute weighted avg.
 255/255 = 100% saturated… 40/255 = 16% capacity
 txload = outbound, rxload = inbound

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CCNA2:CHAPTER 9
CALCULATING EIGRP METRIC
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CCNA2:CHAPTER 9
BANDWIDTH CALCULATION
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CCNA2:CHAPTER 9
DELAY CALCULATION
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CCNA2:CHAPTER 9
EIGRP METRIC CALCULATION
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CCNA2:CHAPTER 10
LINK STATE
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CCNA2:CHAPTER 10
REQUIREMENT OF LINK-STATE ROUTING
PROTOCOLS
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CCNA2:CHAPTER 11
OSPF
AD = 110
 Enabling OSPF

OSPF is enabled with the router ospf process-id
command.
 Process id = number between 1 and 65535
 Process-id is locally significant does not have to
match other ospf routers

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CCNA2:CHAPTER 11
OSPF’S NETWORK COMMAND
Any interfaces on a router that match the network
address in the network command will be enabled to
send and receive OSPF packets.
 This network (or subnet) will be included in OSPF
routing updates.

Router(config-router)#network network-address wildcard-mask
area area-id
 An OSPF area is a group of routers that share link-state
information. (Must be the same on all router in the same network)

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CCNA2:CHAPTER 11
OSPF ROUTER ID

Uniquely identify each router in the OSPF routing
domain
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DETERMINING
OSPF ROUTER ID
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DETERMINING
OSPF ROUTER ID (2)
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CCNA2:CHAPTER 11
VERIFYING OPSF NEIGHBOR






Neighbor ID - The router ID of the neighboring router.
Pri - The OSPF priority of the interface.
State - FULL state means that the router and its neighbor have
identical OSPF link-state databases. (More in CCNP).
Dead Time - The amount of time remaining that the router will
wait to receive an OSPF Hello packet from the neighbor before
declaring the neighbor down. This value is reset when the
interface receives a Hello packet.
Address - The IP address of the neighbor's interface to which this
router is directly connected.
Interface - The interface on which this router has formed
adjacency with the neighbor.
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CCNA2:CHAPTER 11
VERIFYING OSPF
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CCNA2:CHAPTER 11
VERIFYING OSPF
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CCNA2:CHAPTER 11
VERIFYING OSPF
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CCNA2:CHAPTER 11
OSPF METRIC

The Cisco IOS uses the cumulative bandwidths of the
outgoing interfaces from the router to the destination
network as the cost value.
Cost = (Reference Bandwidth)/(Bandwidth in bps)
 Reference Bandwidth = 108 bps

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CCNA2:CHAPTER 11
OSPF ACCUMULATE COST
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SPECIFYING THE BANDWIDTH
CCNA2:CHAPTER 11
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CCNA2:CHAPTER 11
MODIFYING THE LINK COST
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CCNA2:CHAPTER 11
MODIFY REFERENCE BANDWIDTH
BEFORE
AFTER
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CCNA2: Activities
RECOMMENDED ACTIVITIES
3.2.5 Convergence
 3.5.1 Identifying Element of the Routing Table
 4.1.4 Routing Protocol Learning Check
 7.2.4 Verifying RIPv2 Updates
 9.2.6 Configure and Verify EIGRP Routing
 9.6.1 Basic EIGRP Configuration Lab
 11.2.6 Configure and Verify OSPF Routing
 11.6.1 Basic OSPF Configuration Lab

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