13. eigrp and ospf
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13. eigrp and ospf






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13. eigrp and ospf 13. eigrp and ospf Presentation Transcript

  • Enhanced IGRP (EIGRP) and Open Shortest Path first (OSPF)
  • EIGRP  EIGRP is a classless routing protocol.  It is a Cisco protocol.
  • 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.
  • 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.
  • Hop counting  EIGRP has a maximum hop count of 255. (the default is set to 100)
  • 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)
  • 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.
  • 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.
  • EIGRP table  EIGRP maintains 3 types of table to maintain neighbor’s information –  1. topology table  2. neighbor table  3. routing table
  • RTP  Reliable Transport Protocol  EIGRP uses a protocol called RTP.  This protocol is used to manage the communication of message between EIGRP- speaking routers.
  • DUAL  Diffusing update algorithm  EIGRP uses DUAL for selecting and maintaining the best path to each remote network.
  • 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.
  • Route Discovery and maintenance  The hybrid nature of EIGRP is fully revealed in its approach to route discovery and maintenance.
  • 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
  • Route Discovery and maintenance  Neighbor ship table The neighbor ship table records information about routers with whom neighbor ship relationship have been formed.
  • Route Discovery and maintenance  Topology table -: The topology table stores the route advertisements about every route in the internetwork received from each neighbor.
  • Route Discovery and maintenance  Route table -: The route table stores the routes that are currently used to make routing decisions.
  • EIGRP metrics  There are 4 types of metrics – 1. Bandwidth 2. Delay 3. Load 4. Reliability
  • 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
  • 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
  • Configuring EIGRP  # config t  # router eigrp 20  # network  # network  # ctrl+z  #copy run start
  • Passive-interface command  # router eigrp 20  # passive-interface s 0/1/0  ctrl+z  # copy run start
  • 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
  •  # show ip route eigrp  This command shows only EIGRP entries in the routing table. # show ip eigrp neighbors  This command shows all eigrp neighbors.
  •  # show ip eigrp tolopogy  This command shows entries in the EIGRP topology table. # debug eigrp packet  Shows hello packets sent/received between adjacent routers
  •  # debug ip eigrp notification This command shows EIGRP changes and updates as they occur on your network.
  • Successor path  Primary route to reach destination.  Routing table contains this successor path information.
  • Feasible successor  Backup route to reach the destination.  Topology table contains feasible successor path information.
  • DUAL FSM  DUAL finite state machine.
  • 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.
  • Hello packets  EIGRP uses small hello packets.  Hello packets are sent every 5 seconds by default.
  • RTP  Reliable transport protocol  RTP supports unicast and multicast. ------------------------
  • OSPF  Open shortest path first  If you have multiple routers and not all of them are Cisco, then we can not use EIGRP.
  • Dijkstra algorithm  OSPF works by using the dijkstra algorithm.
  • Wild card # conf t # router ospf 1 # network area 0 #network area 0 Ctrl+z # copy run start
  • OSPF Terminology  Link –  a link is network or router interface assigned to any given network.
  •  router id -  the router ip is an IP address used to identify the router.
  •  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.
  •  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.
  •  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
  •  Neighborship database -  The Neighborship database is a list of all OSPF routers for which hello packets have been seen.
  •  topological database -:  The topological database contains information from all of the link state advertisement packets that have been received for an area.
  •  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.
  •  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.
  •  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.
  • Enabling OSPF  There are two basic elements of OSPF configuration- 1. Enabling OSPF 2. Configuring OSPF
  • 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.
  • OSPF configuration  # conf t  (config)# router ospf 1 (1 is process ID)  (config)# network area 1  # copy run start
  •  # 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