a simple question about ospf and eigrp

[ilies-bekhtaoui13]

hello guys i was quite lost about the differences between ospf and eigrp , i mean they both practically work the same in a basic level 

i mean they both have a neighbor tables so why one is called neighbor table and another one contiguity table , why do we name LSA in ospf for advertisement packets and not eigrp , when all they do is send advertisement to other neighbors and and exchange updates after ?i mean at this level they both do the same things so why do they have different names for the same tasks because it made me get lost , is there a different and i'm totally out the line or i'm i right ? 

EDIT also guys what's the difference between contiguity table and link state table ?

[Julio E. Moisa]

Hi

Basically EIGRP and OSPF has the same purpose: interconnect networks and both are IGP (interior gateway protocol). But they are so different s.

Eigrp is a vector distance protocol, Cisco propietary. it works with 3 tables: neighbor, topology and routing table. EIGRP uses administrative distance 90 for internal routes and 170 for routes learned externally by other routing protocols. Also I can mentioned it uses differents metrics than OSPF, They are: Bandwidth, delay, load, MTU and reliability. But by default Bandwidth and Delay are enabled only. When a change occurs only this change is propagated.

EIGRP packet types: hello/ack, update, query, request and replies.

OSPF is a link state protocol, this kind of protocols like (OSPF, IS-IS routing protocols) have a picture of the entire topolog, an OSPF router handles information about itself and the state of the links. OSPF uses the Dijkstra algorithm to find the shortest path based in costs. Each interface in an OSPF environment is assigned a cost based in its bandwidth. The cost is the metric used by OSPF.

OSPF administrative distance is 110. Now OSPF uses LSA, it offers a description of a link or a router, also they can represent external prefixes, in few words to exchange topology information. 

About the tables, OSPF uses 3 tables: routing table, neighbor table and database table. The last one includes the prefixes learned and their LSA types. 

In order to keep and order OSPF assign routers called Designed Router and Backup Designed Router in this way you will have a centralized point to exchage network information. OSPF works with areas and the main area or backbone area is the area 0, so each non backbone are must be connected to the area 0.

These both routing protocols have extensive information. 

The following links could be useful: 

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/13669-1.html

http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7039-1.html

http://www.routeralley.com/guides/ospf.pdf

http://study-ccna.com/designated-backup-designated-router/

http://study-ccna.com/ospf-overview/

Please don't forget to rate the comment if it is useful

:-)

[ilies-bekhtaoui13]

thanks men for such a answer but i will ask you more questions if you want 

well the database contain the routes obtained when using getting neighbor lsa's right ? then does the database also contain the directly connected interfaces of the router it self? does the neighbor contain only the the routers that uses the same routing protocol only ? also is Dijkstra algorithm uses as part of the SPF or the other way around , also i have read in a topic that RIP have a data base also ? i mean as i remember it only have a routing table   , thanks again men 

[Julio E. Moisa]

Hi

Anytime my friend   :-)

The OSPF Database includes the internal or external (LSA 5 or 7) routes learned by other OSPF routers. For example:

sh ip ospf database

OSPF Router with ID (3.3.3.3) (Process ID 1)

Router Link States (Area 0)

Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 1765 0x8000000B 0x00F6EB 2
2.2.2.2 2.2.2.2 1773 0x8000000B 0x0013C0 2
3.3.3.3 3.3.3.3 1608 0x8000000B 0x009BEF 3

Net Link States (Area 0)

Link ID ADV Router Age Seq# Checksum
10.23.0.3 3.3.3.3 1608 0x80000009 0x00FF05

Each OSPF router in a area creates  LSA type 1, it represent the directly connected links and routers which the router has a relationship. 

About RIP, yes it creates a database and it includes the directly connected and learned subnets.

sh ip rip database
1.0.0.0/8 auto-summary
1.1.1.1/32 directly connected, Loopback0
10.0.0.0/8 auto-summary
10.10.10.10/32
[1] via 10.12.0.2, 00:00:17, FastEthernet0/3.

Hope it is useful

:-)

[Joseph W. Doherty]

... ospf and eigrp , i mean they both practically work the same in a basic level 

Beyond populating a route table, and sharing some concepts and goals, at the most basic level, they work very differently.

As often the case with computer technology terminology, sometimes the same concept is named differently.  For example, what most would call a computer "file" on an IBM mainframe is known as a "dataset", or what many might call on a computer a "folder" is also pretty often known as a "directory".

Routing protocol technology, unfortunately often has this issue too.