❑ EIGRP(Enhanced Interior Gateway Routing Protocol)
❍ Overview : A dynamic routing protocol based on distance vector protocol, but also uses link state protocol.
* Improved protocol from IGRP.
* Generally, Cisco network equipments are available.
* Protocol number : 88
❍ Network shape
- Routers with the same AS number consistute one network.
- The update is performed between routers with the same AS number.
❍ How it works
- How to route : Packets are transmitted to path with the lowest metric value.
- Metric calculation : DUAL(Diffusing Update Algorithm) algorithm is used that is mainly based on bandwidth and delay.
- Routing information update
· Partial update : If changes are detected on the link state, only those changes are updated.
* Link state : The interface state that includes IP address, subnet mask, cost etc.
· Bounded update : The update is performed between routers with the same AS number.
❍ EIGRP related word
- FD(Feasible Distance) : Optimal metric value from source to destination.
- AD(Advertised Distance) = RD(Reported Distance) : Optimal metric value from source's next hop router to destination.
- Successor : The next hop router of optimal path.
- Feasible Successor : The next hop router of optimal path except the successor.
❍ EIGRP packet
- Hello : The packet for establishing a neighbor relationship with neighboring routers.
- Update : The packet for transmitting routing information.
- Query : The packet for requestting routing information.
- Reply : The packet for replying to the query packet.
- Ack : The packet for acknowledgment of a packet except hello packet.
* EIGRP uses multicast address 224.0.0.10 for sending a packet to many.
❍ How to configure : View the EIGRP configuration.
❑ OSPF(Open Shortest Path First)
❍ Overview : A dynamic routing protocol based on link state protocol.
* It is supported by all routers.
* Protocol number : 89
❍ Network shape
- Routers with the same area number consistute one network.
- The other areas are connected to the backbone area(Area 0).
- The update is performed between routers with the same area number.
❍ How it works.
- How to route : Packets are transmitted to path with the lowest metric value.
- Metric calculation : Dijkstra algorithm is used that is based on the cost(Bandwidth).
- Routing information update
· Partial update : If changes are detected on the link state, only those changes are updated.
* Link state : The interface state that includes IP address, subnet mask, cost etc.
· Link state Refresh : The routing information is updated every 30 minutes even if no change occurs.
- DR/BDR Election
· The router with the highest OSPF priority value is DR. The next highest router is BDR.
· If the OSPF Priority values are all the same, the router with the highest router ID is DR. the next highest router is BDR.
❍ OSPF related word
- LSA(Link-State Advertisement) : Information that stores changes of the link state. It is encapsulated by the OSPF packet header.
- BR(Backbone router) : A router in the backbone area(Area 0).
- IR(Internal Router) : A router belonging to only one area.
- ABR(Area Border Router) : A router belonging to two or more area. It is located in area boundary.
- ASBR(AS boundary Router) : A routers with OSPF and other routing protocols. It is located in AS boundary.
- DR(Designated Router) : A router to distribute LSA information.
- BDR(Backup Designated Router) : A router to distribute LSA information when DR does not operate.
- DROTHER : Routers except DR and BDR. DROTHER sends and receives LSA information with DR/BDR if the DR/BDR exist.
❍ OSPF packet
- Hello : The packet for establishing a neighbor relationship with neighboring routers.
- DBD(DataBase Description) : The packet for data synchronization. It stores links state information.
- LSR(Link-State Request) : The packet for requesting detailed information(LSA) when there is a route that doesn't exist after receiving DBD packet.
- LSU(Link-State Update) : The packet for replying to LSR packet. It includes LSA.
- LSAck(Link-State Acknowledgement) : The packet for acknowledgment of a packet except hello packet.
* OSPF uses multicast address 224.0.0.5 and 224.0.0.6 for sending a packet to many.
❍ How to configure : View the OSPF configuration.