Communication data routing review --ospf

 Communication data routing review --ospf

ospf review

Today's review ospf

full name is called ospf Open Shortest Path First protocol , which is based on the link state of the Interior Gateway Routing Protocol.
ospf support divided areas , internal router uses spf shortest path algorithm to ensure that the intra-regional loop-free.

ospf features:

1 loop-free: to support regional division
2 fast convergence: support triggered update
3 with good scalability: partitioning features of ospf
4 supports authentication: provides authentication

 

ospf principle introduction

ospf requires each operating ospf router have to understand the entire network link state information , so that it can calculate the optimal route to a destination arrival.
This function is based on:

• Link State Advertisements LSA (Link State Advertisement) to gather information
• To establish their own collection of information based on LSA link state database the LSDB (Link State Database)
• Using S based on the LSDB PF calculation algorithm to reach each network establish a shortest path tree.

ospf packets are encapsulated in IP packets, protocol number 89

 

ospf neighbor and DR

• Router ID: is a 32-bit value that uniquely identifies a router in the autonomous system
• Neighbor (Neighbor): interface to send Hello packets to discover neighbors by ospf
• Adjacent (Adjacency): Only two sides successfully exchange DD packets, and can exchange LSA

The router sends an LSA must before to discover neighbors and establish neighbor relations

DR and BDR may reduce the number of adjacencies, thus reducing the number of exchanges routing information, saving bandwidth.

DB is a port-based routing priority to elections. The higher the value, the higher the priority . Compare Router ID may also apply.

ospf area

Area0 is the backbone of the region , other regions must be connected to this area

ospf cost

ospf-based interface bandwidth calculation cost : calculated as: Cost = Reference bandwidth value Interface ÷ bandwidth.

 

ospf configuration　

[RTA] ospf router-id 1.1.1.1 // enable ospf configuration and process ID
[-ospf-the RTA. 1] The ospf area Area 0 //
[RTA-ospf-1-area -0.0.0.0] network 192.168.1.0 Interface 0.0.0.255 // specify a running ospf protocol specifies a reverse mask , for matching address value.

Configuration Validation

[RTA ] display ospf peer

• Command display ospf peer may be used to check the neighbor related attributes, including regional, state neighbor, adjacent to the main negotiation state, and from the DR and BDR situation.

ospf authentication

[RTA -GE0/0/0] ospf authentication-mode md5 1 huawei

• OSPF authentication can be disposed on the interface or region , an interface mode has higher priority than the authentication area authentication.

Configuration Validation

<RTA>terminal debugging
<RTA> debugging ospf packet

• debugging ospf packet command to debug OSPF packets, and then they can view the certification process to determine whether the successful authentication configuration.

problem:

1, ospf hello packets Router Dead Interval field is what role?
Answer: Router Dead Interval field represents the Hello packet interval of death, if at this time
is not received from the neighbor's Hello packet between, the neighbor is considered invalid. Dead interval is
four times the Hello interval, on the broadcast network default of 40 seconds (as default Hello interval
10 seconds).

2, in a broadcast network, DR and BDR to receive a link state update packets what address?
A: On a broadcast network, DR, and use the multicast address 224.0.0.6 BDR to receive link state
update packets.