Routing Protocol RIPv1, RIPv2, EIGRP OSPF 2 Outline o RIPv1, RIPv2 o EIGRP o OSPF 3 RIPv1 RIP Characteristics • A classful, Distance Vector (DV) routing protocol • Metric = hop count • Routes with a hop count > 15 are unreachable • Updates are broadcast every 30 seconds 4 RIPv1 RIP Message Format RIP header - divided into 3 fields - Command field - Version field - Must be zero Route Entry - composed of 3 fields - Address family identifier - IP address - Metric
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Routing Protocol RIPv1, RIPv2 EIGRP o OSPF · Routing Protocol RIPv1, RIPv2, EIGRP OSPF 2 Outline o RIPv1, ... Difference between RIPv1 & RIPv2 ... VLSM & CIDR oRIPv2 and VLSM
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Routing Protocol
RIPv1, RIPv2, EIGRP OSPF
2
Outline
o RIPv1, RIPv2
o EIGRP
o OSPF
3
RIPv1
RIP Characteristics
• A classful, Distance Vector (DV) routing protocol
• Metric = hop count
• Routes with a hop count > 15 are unreachable
• Updates are broadcast every 30 seconds
4
RIPv1�RIP Message Format
�RIP header - divided into 3 fields
- Command field
- Version field
- Must be zero
�Route Entry - composed of 3 fields
- Address family identifier
- IP address
- Metric
5
RIPv1
RIP Operation
RIP uses 2 message types:
�Request message
• This is sent out on startup by each RIP enabled
interface
• Requests all RIP enabled neighbors to send routing
table
�Response message
• Message sent to requesting router containing routing
table6
RIP in action
RIP request
dst. 255.255.255.255
RIP reply
dst. request router every 30 sec.
7
RIPv1
o IP addresses initially
divided into classes
- Class A
- Class B
- Class C
o RIP is a classful
routing protocol
- Does not send subnet
masks in routing updates
8
Automatic SummarizationBoundary Routers
� RIP automatically summarizes classful networks
� Boundary routers automatic summarize RIP subnets from one major network to another.
9
RIPv2Difference between RIPv1 & RIPv2
RIPv1• A classful distance vector routing protocol
• Does not support discontiguous subnets
• Does not support VLSM
• Does not send subnet mask in routing update
• Routing updates are broadcast
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
• The use of authentication is an option
10
Similarities between RIPv1 & RIPv2
o Use of timers to prevent routing loops
o Use of split horizon or split horizon with poison reverse
o Use of triggered updates
o Maximum hop count of 15
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RIPv1 Limitations
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RIPv1 Limitations
o RIPv1 – a classfull routing protocol
-Subnet mask are not sent in updates
-Summarizes networks at major network boundaries
-if network is discontiguous and RIPv1 configured,
acknowledgment from destination� Unreliable delivery does not require
an acknowledgement from destination
� Packets can be sent � Unicast� Multicast
• Using address 224.0.0.1034
EIGRP Packet Types
o EIGRP uses five different packet types, some in pairs.
� Hello Packets
� Update Packets
� Acknowledgement Packets
� Query and Reply Packets
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EIGRP Packet Typeso Hello packets
� Used to discover & form adjacencies with neighbors
� Hello packets are multicasts and use unreliable delivery.
36
EIGRP Packet Types
o Update packets
� Used to propagate routing
information
� Unlike RIP, EIGRP does not
send periodic updates. Update
packets are sent only
when necessary.
o ACK packets
� Used to acknowledge
receipt of update,
query & reply packets
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EIGRP Packet Types
o Query & Reply packets
�Used by DUAL for
searching for networks
�Query packets
- Can use
•Unicast
•Multicast
�Reply packet
- Use only
•unicast
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EIGRP – Hello Protocol o Purpose of Hello Protocol
� To discover & establish adjacencies with neighbor routers
o Characteristics of hello protocol� Time interval for sending hello packet
�Most networks it is every 5 seconds
�Multipoint non broadcast multi-access networks• Unicast every 60 seconds
- Holdtime� This is the maximum time router
should wait before declaring a neighbor down
� Default holdtime
• 3 times hello interval
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EIGRP – Bounded Updateso EIGRP only sends update when there is a change in route status
o Routing update is called “Partial update”� A partial update includes only the route information that has
changed – The whole routing table is NOT sent
o and also considered as “Bounded update”� When a route changes, only those devices that are impacted will
be notified of the change
o EIGRP’s use of partial bounded updates minimizes use of bandwidth
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EIGRP – DUAL
Diffusing Update Algorithm (DUAL)
� Purpose
• EIGRP’s primary method for preventing routing loops
� Advantage of using DUAL
• Provides for fast convergence time by keeping a list of
loop-free backup routes
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EIGRP
o Administrative Distance (AD)
� Defined as the trustworthiness of the source route
o EIGRP default administrative distances
� Summary routes = 5
� Internal routes = 90
� Imported routes = 170
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EIGRP
Authentication
o EIGRP can
� Encrypt routing information
� Authenticate routing information
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EIGRP
o Topology Example
44
EIGRP
o EIGRP will
automatically
summarize routes at
classful boundaries
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Basic EIGRP Configuration o Autonomous System (AS) & Process IDs
� Autonomous System
� This is a collection of networks under the control of
a single authority (reference RFC 1930)
� AS Numbers are assigned by IANA
� Entities needing AS numbers
� ISP
� Internet Backbone prodiers
� Institutions connecting to
other institutions using
AS numbers
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Basic EIGRP Configuration
o EIGRP autonomous
system number actually
functions as
a process ID
o Process ID represents
an instance of the
routing protocol
running on a router
o Example Router(config)#router eigrp autonomous-
system
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Basic EIGRP Configuration
The router eigrp command
o All routers in the EIGRP routing domain must use the same process ID number (autonomous-system number)
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Basic EIGRP ConfigurationThe Network Command
o Functions of the network command� Enables interfaces to transmit & receive EIGRP updates
� Includes network or subnet in EIGRP updates
o Example: Router(config-router)#network network-address
o When EIGRP is configured on R2, DUAL sends a notification message to the console stating that a neighbor relationship with another EIGRP router has been established.
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Basic EIGRP ConfigurationThe network Command with a Wildcard Mask
- This option is used when you want to configure EIGRP to
o Delay – EIGRP uses the cumulative sum of all outgoing
interfaces
� Calculated Delay = the sum of outgoing interface delays
* 256
o EIGRP Metric = calculated BW + calculated delay
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EIGRP Metric Calculation
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EIGRP Metric Calculation
Link Bandwidth
(kbps)
Delay (µµµµs)
R2 – R1 1,544 20,000
R2 – ISP 128 20,000
R2 – R3 1,024 20,000
R1 – ISP 10,000 1,000
R3 – ISP 100,000 100
ISP – Net A 100,000 100
(107/ 1,544) x 256 1,657,856 (107/ 64) x 256 40,000,000
(107/ 1,024) x 256 2,499,840 (107/ 10,000) x 256 256,000
(107/ 128) x 256 20,000,000 (107/ 100,000) x 256 25,600
Example : R2 to Network A
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DUAL Briefo EIGRP uses the Diffusing Update Algorithm (DUAL).
o EIGRP does not send periodic updates and route entries do not age out.
o EIGRP uses a lightweight Hello protocol to monitor connection status with its neighbors.
o Only changes in the routing information, such as a new link or a link becoming unavailable cause a routing update to occur.
o EIGRP's DUAL maintains a topology table separate from the routing table, which includes both the best path to a destination network and any backup paths that DUAL has determined to be loop-free.
o Loop-free means that the neighbor does not have a route to the destination network that passes through this router.
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DUAL Concepts
The Diffusing Update Algorithm (DUAL) is
used to prevent looping
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DUAL Conceptso Successor
a neighboring router that is used for packet forwarding and is the least-cost route to the destination network
o Feasible distance
the lowest calculated metric to reach the destination network
FD is the metric listed in the routing table entry
� EIGRP is a derivative of IGRP�EIGRP is a Cisco proprietary distance vector routing
protocol released in 1994
o EIGRP terms and characteristics
� EIGPR uses RTP to transmit & receive EIGRP packets
� EIGRP has 5 packet type:�Hello packets
�Update packets
�Acknowledgement packets
�Query packets
�Reply packets
� Supports VLSM & CIDR
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Summary
o EIGRP terms and characteristics
� EIGRP uses a hello protocol
�Purpose of hello protocol is to discover & establish
adjacencies
� EIGRP routing updates
�Aperiodic
�Partial and bounded
�Fast convergence
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Summary
o EIGRP commands
� The following commands are used for EIGRP configuration
RtrA(config)#router eigrp [autonomous-system #]
RtrA(config-router)#network network-number
� The following commands can be used to verify EIGRP
Show ip protocols
Show ip eigrp neighbors
Show ip route
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Summary
o EIGRP metrics include
�Bandwidth (default)
�Delay (default)
�Reliability
�Load
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Summary
o DUAL
� Purpose of DUAL�To prevent routing loops
� Successor�Primary route to a destination
� Feasible successor�Backup route to a destination
� Feasible distance�Lowest calculated metric to a destination
� Reported distance�The distance towards a destination as advertised by an
upstream neighbor
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Summaryo Choosing the best route
� After router has received all updates from directly connected neighbors, it can calculate its DUAL
�1st metric is calculated for each route
�2nd route with lowest metric is designated successor & is placed in routing table
�3rd feasible successor is found
• Criteria for feasible successor: it must have lower reported distance to the destination than the installed route’s feasible distance
• Feasible routes are maintained in topology table94
Summary
o Automatic summarization
�On by default
�Summarizes routes on classful boundary
�Summarization can be disabled using
the following command
RtrA(config-if)#no auto-summary
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Link-State Routing
o Link state routing protocols
• Also known as shortest path first algorithms
• These protocols built around Dijkstra’s SPF
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Link-State Routing
Dikjstra’s algorithm also known as the shortest path first
(SPF) algorithm
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Link-State Routing
o The shortest path to a destination is not necessarily
the path with the least number of hops
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Link-State Routing Protocols
2 link state routing protocols used for routing IP
� Open Shortest Path First (OSPF)
� Intermediate System-Intermediate System (IS-IS)
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OSPF
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OSPFBackground of OSPF
o Began in 1987
o 1989 OSPFv1 released in RFC 1131
This version was experimental & never deployed
o 1991 OSPFv2 released in RFC 1247
o 1998 OSPFv2 updated in RFC 2328 (current version)
o 1999 OSPFv3 published in RFC 2740 (for IPv6)
101
OSPF packetOSPF Message Encapsulationo OSPF packet type
There exist 5 typeso OSPF packet header
Contains - Router ID and area ID and Type code for OSPF packet type
o IP packet header
Contains - Source IP address, Destination IP address, & Protocol field set to 89
� Data link frame header
Contains - Source MAC address and Destination MAC address
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OSPF Packet Types
1. Hello - Hello packets are used to establish and maintain adjacency with other OSPF routers.
2. DBD - The Database Description (DBD) packet contains an abbreviated list of the sending router's link-state database and is used by receiving routers to check against the local link-state database.
3. LSR - Receiving routers can then request more information about any entry in the DBD by sending a Link-State Request (LSR).
4. LSU - Link-State Update (LSU) packets are used to reply to LSRs as well as to announce new information. LSUs contain seven different types of Link-State Advertisements (LSAs).
5. LSAck - When an LSU is received, the router sends a Link-State Acknowledgement (LSAck) to confirm receipt of the LSU.
103
OSPF
Hello Protocol : OSPF Hello Packet
� Purpose of Hello Packet
• Discover OSPF neighbors & establish adjacencies
• Before two routers can form an OSPF neighbor adjacency, they must agree on three values: Hello interval, Dead interval, and network type.
• Advertise guidelines on which routers must agree to become neighbors
• Used by multi-access networks to elect a designated router and a backup designated router
104
OSPF
105
OSPFo Hello Packets continued
Contents of a Hello Packet, router ID of transmitting routero OSPF Hello Intervals
� Usually multicast (224.0.0.5 = all OSPF routers)
� Sent every 10 seconds on multiaccess and point-to-point segments and 30 seconds for NBMA (non broadcast multiple-access) segments
o OSPF Dead Intervals
� This is the time that must transpire
before the neighbor is considered
down
� Default time is 4 times
the hello interval
106
OSPF
o Hello protocol packets contain information that is
used in electing
� Designated Router (DR)
- DR is responsible for updating all other OSPF routers
� Backup Designated Router (BDR)
- This router takes over DR’s responsibilities if DR fails
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OSPF Link State Updateo Purpose of a Link State Update (LSU)
Used to deliver link state advertisementso Purpose of a Link State Advertisement (LSA)
Contains information about neighbors & path costs
108
OSPF Algorithm
o OSPF routers build & maintain
link-state database containing
LSA received from other
routers
� Information found in database
is utilized upon execution of
Dijkstra SPF algorithm
� SPF algorithm used to create
SPF tree
� SPF tree used to populate
routing table
109
OSPF Administrative Distance
o Default Administrative Distance for OSPF is 110
110
OSPF Authentication� Purpose is to encrypt & authenticate routing information
� This is an interface specific configuration
�Routers will only accept routing information from other routers that have been configured with the same password or authentication information
111
Basic OSPF Configuration
o Topology Example
• Discontiguous IP addressing scheme
• Since OSPF is a classless routing protocol the subnet mask is configured in
112
Basic OSPF ConfigurationThe router ospf command
o To enable OSPF on a router use the following command
R1(config)#router ospf process-id
Process id
� A locally significant number between 1 and 65535
this means it does not have to match other OSPF routers in order to establish adjacencies with those neighbors.