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OSPF protocol for dynamic routing. Internal and external Gateway protocols for routing Overview

Internal gateway protocol and external gateway protocol 1. Zoning management, autonomous system (AS) so many routes. two。 Interior Gateway Protocol (IGP) RIP OSPF ISIS runs in their own internal areas but cannot communicate in different areas. External Gateway Protocol (EGP) BGP has only one protocol, such as Alibaba Feitian wants to communicate through the external protocol BGPECS is Alibaba's CVM 2.ospf is a link-state routing protocol

OSPF is a link-state routing protocol. Each link is a directly connected segment of a router. It knows all the packet information. They will exchange information with each other and generate a routing table, but the link state is transmitted. It also contains network segment information, which is different from RIP, in which RIP learns routing tables from each other. The link state (LSA) is the description information on the OSPF interface, such as the IP address on the interface, the subnet mask, the network type, the Cost value and so on. What the OSPF routers exchange is not the routing table, but the link state (LSA). By obtaining all the link state information in the network, OSPF calculates the exact network path to each destination. The working process of 3.OSPF

Ospf shortest path first selection Protocol path cost bandwidth is higher, path cost is lower 4.OSPF area

Five regional backbone areas, standard areas, stub areas, stub areas, non-stub areas, these are all non-backbone regional running LSA protocol 5.ROUTER ID selection rules.

If there is no Loopback interface, choose the one with the highest IP address in the physical port, but there is something wrong with the interface, ID will have no Ip address and 6.DR and BDR will be invalid.

The roles of routers DR and BDR establishing adjacencies in broadcast networks even if one route fails the middle router of a star, several routers are scattered and connected to the boss DR to send instructions to count the status of each link BDR second backup 7.DR and BDR selection method

The largest router of RouterID on the network segment will be elected bit DR, and the second largest will be elected bit BDR. In the real environment, who starts OSPF first is DR, so generally priority is to enable DR. 8.ospf Multicast address ospf Multicast address 224.0.0.5 Boss receives this interface disconnect message and sends it to other routes 224.0.0.6 listening router information such as an interface break, he knows first and then sends the metric to DR boss 9.OSPF

OSPF metric COSTcost=10 to the power of 100 megabytes divided by the cost of the bandwidth path 10.OSPF five packet types

How 11.OSPF adjacency routers work

1.down status R1 sends hello packets R2 from down state to initialization state 2.Init interacts with each other DR and BDR election 3. 2way only selects the two largest, 4.EXsrart status quasi-startup state we will determine DR and BDR5. They are familiar with each other to send DBD messages, link state 6.Exchange state out of DBD and LSAck confirmation 7.loading state except HEllo,Dbd other packets have 8.FULL state, algorithm, routing table will enter this state after 12.OSPF divides the network into four types

Characteristics and use of 13.OSPF

The above are all single-area II. OSPF multi-area overview

Three kinds of traffic of 1.OSPF

Ospf area division is divided according to the router interface, so a router can belong to multiple areas. ISIS is divided by route. ABR is responsible for the transmission of inter-domain traffic. ASBR is responsible for the transmission of traffic outside the domain. 2.OSPF area type.

3. LSA type

TYPE1 router LSA: all routers in the area send link information TYPE2 network LSA: the DR in the area sends out announcement network information, and a network segment is added, deleted, and changed, which is first known and then sent to DR, and then sent to all TYPE3 network summary LSA: route summary information exchange between ABR areas has 5, 4, 2 are bundled TYPE4 ASBR summary LSA: ABR tells other routers the location of ASBR Dealing with other AS external LSA: ASBR tells the internal and external routing information, tells the external internal TYPE7 NSSA external LSA: only in the NSSA area, non-storage stub area, 1.2 each area has 3.4.5 some areas have, some areas do not have, 74.OSPF commonly used check commands

5. Stub area and complete stub area

6. Route redistribution

7. Two types of paths that are redistributed to OSPF protocol routes

three。 Let's summarize the four routing types of OSPF, the five backbone areas, the standard area, the stub area, the stub area, the non-stub area, these are all non-backbone areas, run LSA protocol five, big data packet type hello DBD LSR LSU (including multiple LSA) LSACKHello packets: used to discover and maintain neighbor relationships, elect DR and BDR. Database description package (DBD): used to send summary information to neighbors to synchronize the link-state database. Link-state request packet (LSR): sent after the router receives a DBD containing new information to request more detailed information. Link-state update packet (LSU): a link-state advertisement (LSA) is sent when a LSR is received. A LSU packet may contain multiple LSA. Link-state acknowledgement packet (LSAck): acknowledges that LSU has been received, and each LSA protocol is acknowledged separately. Six kinds of LSA TYPE1 router LSA: all routers in the area send link information TYPE2 network LSA: DR in the area sends out announcement network information, and one network segment is added, deleted, changed. I first know it and then send it to DR, and then send it to all TYPE3 network summary LSA: five out of five routing summary information exchanges between ABR areas, four are bundled TYPE4 ASBR summary LSA: ABR tells other routers the location of the ASBR, TYPE5 AS external LSA: ASBR tells internal and external routing information, external TYPE7 NSSA external LSA: only available in NSSA areas, non-stub areas 1.2 each area has 3.4.5 some areas have, some areas do not have, 7 seven states 1, Down status: did not receive Hello message 2, Init status: received Hello message activation startup router 3, 2-Way status: elect the two largest RouterID But did not confirm DR and BDR4, ExStart status (quasi-startup state): confirm master-slave routing (confirm DR and BDR) 5, Exchange status: exchange messages (DBD and LSAck) 6, Loading status: in addition to Hello and DBD, run other messages such as LSR message, LSU message (most abundant state-load state) 7, Full status: algorithm, routing table generation # is part of our OSPF protocol. In the next two chapters, we will synthesize experiments. Single area OSPF configuration, multi area OSPF configuration, virtual link.

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