EIGRP and OSPF are hybrid and link-state routing protocols respectively. EIGRP uses the DUAL algorithm and metric system to determine the best paths, while OSPF uses the Dijkstra algorithm and link state advertisements. Both protocols form neighbor relationships to exchange routing information, but OSPF requires adjacencies and is more restrictive in sharing routes between areas.

1. Enhanced IGRP (EIGRP) and Open Shortest
Path first (OSPF)

2. EIGRP
 EIGRP is a classless routing protocol.
 It is a Cisco protocol.

3. AS number
 It uses the concept of an autonomous system to
describe the set of routers that run the same routing
protocol and share routing information.

4. Hybrid routing protocol
 EIGRP is sometimes referred to as a hybrid routing
protocol. Because it has characteristics of both
distance-vector and link-state protocol.

5. Hop counting
 EIGRP has a maximum hop count of 255.
(the default is set to 100)

6. EIGRP features
 It supports for IPv4 and IPv6 .
 Considered classless (same as RIPV2 and OSPF)
 Communication via reliable Transport Protocol.
 Best path selection via Diffusing Update Algorithm
(DUAL)

7. Protocol-dependent modules
 One of the most interesting features of EIGRP is that
it provides routing support for multiple network
protocols: IP, IPX, Apple Talk and now IPv6.
 It is also known as PDM.

8. Neighbor Discovery
 When EIGRP routers receive their neighbors
updates, they store them in a local topology table.
 This local topology contains all known routes from
all known neighbors and serves as the raw material
from which the best routes are selected and placed
into the routing table.

9. EIGRP table
 EIGRP maintains 3 types of table to maintain
neighbor’s information –
 1. topology table
 2. neighbor table
 3. routing table

10. RTP
 Reliable Transport Protocol
 EIGRP uses a protocol called RTP.
 This protocol is used to manage the communication
of message between EIGRP- speaking routers.

11. DUAL
 Diffusing update algorithm
 EIGRP uses DUAL for selecting and maintaining the
best path to each remote network.

12. Multiple ASes
 EIGRP uses autonomous system numbers to identify
the collection of routers that share route
information.
 Only routers that have same autonomous system
numbers share routes.

13. Route Discovery and maintenance
 The hybrid nature of EIGRP is fully revealed in its
approach to route discovery and maintenance.

14. Route Discovery and maintenance
 EIGRP uses a series of tables to store important
information about its environment
1. Neighbor ship table
2. Topology table
3. Route table

15. Route Discovery and maintenance
 Neighbor ship table
The neighbor ship table records information about
routers with whom neighbor ship relationship have
been formed.

16. Route Discovery and maintenance
 Topology table -:
The topology table stores the route advertisements
about every route in the internetwork received from
each neighbor.

17. Route Discovery and maintenance
 Route table -:
The route table stores the routes that are currently
used to make routing decisions.

18. EIGRP metrics
 There are 4 types of metrics –
1. Bandwidth
2. Delay
3. Load
4. Reliability

19. Maximum paths and hop count
 EIGRP can provide equal-cost load balancing of up
to four links.
 We can have EIGRP actually load-balance across
up to six links by using the following command:
R1(config)# router eigrp 10
R1(config-if)# maximum-paths ?
<1-6> number of paths

20. Maximum paths and hop count
 EIGRP has a maximum hop count of 100, but it can
be setup to 255.
 # router eigrp 10
 # metric maximum-hops ?
 <1-255> hop count

21. Configuring EIGRP
 # config t
 # router eigrp 20
 # network 10.0.0.0
 # network 20.0.0.0
 # ctrl+z
 #copy run start

22. Passive-interface command
 # router eigrp 20
 # passive-interface s 0/1/0
 ctrl+z
 # copy run start

23. Verifying EIGRP
 There are several commands that can be used on a
router to help us troubleshoot and verify the EIGRP
configuration.
 # show ip route
 # show ip route eigrp
 # show eigrp neighbors
 # show eigrp topology
 # show eigrp packet
 # debug ip eigrp notification

24.  # show ip route eigrp
 This command shows only EIGRP entries in the
routing table.
# show ip eigrp neighbors
 This command shows all eigrp neighbors.

25.  # show ip eigrp tolopogy
 This command shows entries in the EIGRP
topology table.
# debug eigrp packet
 Shows hello packets sent/received between
adjacent routers

26.  # debug ip eigrp notification
This command shows EIGRP changes and updates
as they occur on your network.

27. Successor path
 Primary route to reach destination.
 Routing table contains this successor path
information.

28. Feasible successor
 Backup route to reach the destination.
 Topology table contains feasible successor path
information.

29. DUAL FSM
 DUAL finite state machine.

30. Working of DUAL FSM
 1. FSM define a set of possible something can go
through, what events causes those states and what
event result from those states.
 DUAL selects alternate routes quickly by using the
information in the EIGRP table.
 If a link goes down, DUAL looks for a feasible
successor in its neighbor and topology table.

31. Hello packets
 EIGRP uses small hello packets.
 Hello packets are sent every 5 seconds by default.

32. RTP
 Reliable transport protocol
 RTP supports unicast and multicast.
------------------------

33. OSPF
 Open shortest path first
 If you have multiple routers and not all of them are
Cisco, then we can not use EIGRP.

34. Dijkstra algorithm
 OSPF works by using the dijkstra algorithm.

35. Wild card
# conf t
# router ospf 1
# network 192.168.0.0 0.0.0.15 area 0
#network 193.168.0.0 0.0.0.3 area 0
Ctrl+z
# copy run start

36. OSPF Terminology
 Link –
 a link is network or router interface assigned to any given
network.

37.  router id -
 the router ip is an IP address used to identify the router.

38.  neighbor –
 neighbor are two or more routers that have an inteface on a
common network, such as 2 routers connected on a point-to-
point serial link.

39.  Adjency –
 an adjency is a relationship between two OSPF routers that
permits the direct exchange of route updates.
 OSPF is really picky about sharing routing information - unlike
EIGRP which directly shares routes with all of its neighbor.
 OSPF directly shares routes only with neighbors that have also
established adjencies.

40.  Hello Protocol -
 the OSPF Hello provides dynamic neighbor discovery and
maintain neighbor relationships.
 hello packets and link state advertiesment (LSA) build and
maintain topological database

41.  Neighborship database -
 The Neighborship database is a list of all OSPF routers for
which hello packets have been seen.

42.  topological database -:
 The topological database contains information from all of the
link state advertisement packets that have been received for an
area.

43.  Link state advertiesment -:
 a link state advertiesment (LSA) is an OSPF data packet
containing link-state and routing information that's shared
among OSPF routers.

44.  OSPF area -:
 an OSPF area is a grouping of networks and routers. all routers
in the same area share a common area id.
 a router can be a member of more than one area at a time.
 all the routers within the same area have the same topology
table.

45.  SPF Tree calculation
 within an area, each router calculates the best/shortest path to
every network in that same area.
 this calculation is based upon the information collected in the
topology database and an algorithm
called shortest path first.

46. Enabling OSPF
 There are two basic elements of OSPF configuration-
1. Enabling OSPF
2. Configuring OSPF

47. Enabling OSPF
 r1(config)# router ospf <1-65535>
 <1-65535> identifies the OSPF process ID.
 It’s a unique number on this router that groups a series
of OSPF configuration commands under a specific
running process.
 Different OSPF routers do not have to use the same
process ID.

48. OSPF configuration
 # conf t
 (config)# router ospf 1 (1 is process ID)
 (config)# network 10.0.0.0 0.255.255.255 area 1
 # copy run start

49.  # show ip ospf database
 # show ip ospf interface
 # show ip ospf neighbor
 # show ip protocols
 # debug ip ospf packet
 #debug ip ospf hello
 #debug ip ospf adj