Various extensions of hcip-9.ospf

OSPF Routing control

priority

[r3-ospf-1]preference 50--- modify OSPF Routing default priority --- This life The command will only affect all types of fields OSPF（OSPF Routing information inside the network ） Routing information for .

[r3-ospf-1]preference ase 100--- Modify the default priority of routes imported outside the domain level .

The above modification , Only for the default priority of the corresponding type of route in the local route table of the device Level .

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open Pin value

COST = Reference bandwidth / Real bandwidth

1, Change the overhead value by modifying the reference bandwidth

[r3-ospf-1]bandwidth-reference 1000 --- Modifying the reference bandwidth requires all OSPF The devices in the network are all changed to the same .

Because once the reference bandwidth is modified , All devices in the whole network have to be modified into one What kind of , therefore , Its essence cannot control the choice of road . Its significance lies in when the real bandwidth more , The reference bandwidth can be increased , Avoid poor routing .

2, The effect of modifying the cost value is achieved by modifying the real transmission rate of the interface

[r3-GigabitEthernet0/0/0]undo negotiation auto --- Turn off auto negotiation

[r3-GigabitEthernet0/0/0]speed 10

Be careful , The command takes effect after restarting the interface

This method can indeed change the size of the cost value for the specified interface , Play a Control the effect of route selection . however , It will affect the real transmission rate of the interface , and And , It can only be reduced , therefore , It is not recommended to make With this scheme .

3, Directly modify the cost value of the interface

[r3-GigabitEthernet0/0/0]ospf cost 1000--- Modify the interface cost value

Be careful ： Because the cost value of the loopback interface is a defined value , therefore , As a result,

Change without external changes , namely 1,2 Neither method will affect the loopback interface

Cost value of . however , The first 3 This method can change the cost value of the loopback interface .

Particular attention ：OSPF The cost value of reaching the target network segment in , Routing information sender

Directed Cost value flowing into the interface The cumulative value of .

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OSPF The appendix E

appendix E It mainly defines a solution in a special case .

appendix E The proposed solution masks a shorter normal entry , And the longer the mask will be his LS  ID Use direct broadcast address to express .

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OSPF The road selection principle

Intra domain ---1 class ,2 class LSA

Inter domain ---3 class LSA

Outside the country ---5 class ,7 class LSA --- type 1、 type 2

1, Intra domain --- If there are multiple passes to reach the same target network segment 1 class ,2 class LSA Learning to

When routing information for , The cost value reaching the target network segment will be compared , Choose the one with low cost . If on

Same pin value , Then the load will be balanced .

2, Inter domain --- If there are multiple passes to reach the same target network segment 3 class LSA Learned routing information , The cost value reaching the target network segment will be compared , Choose the one with low cost . If the cost value is the same , Then the load will be balanced .

3, Outside the country

[r3]display ospf lsdb ase--- You can expand all at once 5 class LSA

type 1： If the cost value type is type 1, Then all devices in the domain reach the target network segment outside the domain

The cost value of is equal to the cost value of the local arrival notifier plus the seed metric .

[r4-ospf-1]import-route rip 1 type 1--- Modify the cost value type when republishing

type 2： If the cost value type is type 2, Then all devices in the domain reach the target network segment outside the domain

The cost value of is equal to the seed measure .

type 1 Always better than type 2.--- The purpose of this design is to More convenient to interfere with route selection .

type 2 The road selection principle ： If there are multiple passes to reach the same target network segment 5 class /7 class

LSA Learned routing information , And the cost value types are all types 2, Compare species first

Sub measure , Give priority to those with small seed metrics ; If the seed measures the same , Then compare

Accumulate the cost value along the way , Give priority to those with small accumulated cost value along the way . If you accumulate expenses along the way

The same value , Load balancing .

type 1 The road selection principle ： If there are multiple passes to reach the same target network segment 5 class /7 class

LSA Learned routing information , And the cost value types are all types 1, Will be more general

expenses （ Seed measure + Accumulate the cost value along the way ）, Give priority to those with low total cost . Such as

If the total cost is the same , Load balancing .

4, Intra domain and inter domain --- If the same destination network segment exists, pass 1 Classes and 2 class LSA Study

To the domain information and through 3 class LSA Learned inter domain information , Will be preferred to pass 1 class

2 class LSA Learned , Even if the cost is more valuable .---- Intra domain is better than inter domain .

5, Interregional and extraterritorial --- If the same destination network segment exists, pass 3 class LSA Learned domain

Information between and through 5 class /7 class LSA Learned foreign information . Will be preferred to pass 3 class

LSA Learned , Even if the cost is more valuable .---- Inter domain is better than extradomain .

6, In the Huawei system ,5 Classes and 7 class LSA The routing rules are the same .

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OSPF My guard ring

Inter domain anti ring                                                                                             

1,OSPF Because routing information is also transmitted between regions , therefore , There are regional horizontal scores

Cutting mechanism . The routing information learned from which region will not be returned to this region .

2, The region division of star topology requires itself to be an anti ring mechanism .

In domain anti ring

OSPF Anti ring mechanism in the domain ---SPF Algorithm --- Shortest path first algorithm

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heavy Release

effect ： In a network , If you run multiple routing protocols or different processes of the same routing protocol

cheng ; The protocols cannot directly communicate with each other, including the independent forwarding and operation between processes ; therefore

You need to republish to realize the sharing of routes .

strip Pieces of :

1, There must be ASBR equipment --- Simultaneous connection Two kinds of Agreement or Two process ; Can be the same as

Learn the routing information on both sides , Then complete the route sharing .

2, We must pay attention to three measures ---A The protocol and B The measurement calculation logic between protocols is illogical ,

Cannot be used directly . So I will A The agreement is published to B When the agreement ,ASBR Will not carry A agreement

Measures to B agreement , It's sharing to B When the agreement , from ASBR The device adds

Add a starting measure .

gauge be :

1, take A The protocol is imported into B When the agreement , Need to be in ASBR Of B Configure republication on the protocol .

2, take A The agreement is published to B When the agreement , Yes, it will ASBR On all the adopt A The agreement learned And

ASBR Announced on A All direct routes of the protocol Share all to B Agreement .

spot

Single point --- Between two protocols or two processes 1 individual ASBR equipment

Bipoint --- Between two protocols or two processes 2 individual ASBR equipment

Multipoint --- There are multiple... Between two protocols or two processes ASBR equipment

towards

A one-way  ---  Only will A The agreement is published to B In the agreement

double towards  --- A/B All routes of the protocol are shared

To configure

A -> B： One dynamic routing protocol is published to another dynamic routing protocol

static state -> B： Import static routes into dynamic routing protocols

Direct connection -> B： Import direct route into dynamic routing protocol

RIP

A -> B： One dynamic routing protocol is published to another dynamic routing protocol

[r2-rip-1]import-route ospf 1

Conclusion ： Through republishing technology, the routing information of other protocols is imported into RIP in , The default seed measure assigned to it is 0.

How to modify the seed measure ：

① Modify the overall situation in the process ：[r2-rip-1]default-cost 2

② Modify for this reissue ：[r2-rip-1]import-route ospf 1 cost 3

Be careful ： When the above two commands are executed at the same time , Will be in accordance with paragraph 2 strip , Match more Precise commands to execute .

static state  - >B: Import static routes into dynamic routing protocols

[r2-rip-1]import-route static

Conclusion ： During the republication process, the default route will not be republished to the dynamic routing protocol .

Direct connection  - >B: Import direct route into dynamic routing protocol

[r2-rip-1]import-route direct

Conclusion ：1, except R1 Outside the direct network segment of , All direct connections will be imported

2, if ASBR the A->B Re release and direct connection ->B Retransmission of cloth , And contain the same routing information twice , Will give priority to learning direct connection ->B Re release information .

[r2-ospf-1]default cost ?

INTEGER<0-16777214> Cost value 

[r2-ospf-1]default type ?

INTEGER<1-2> Type value