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2022-07-20 13:32:00 【Guan Bolan,】

Catalog

OSPF Routing control

priority ：

Cost value ：

OSPF The appendix E 

OSPF The road selection principle

Intra domain

Inter domain

Outside the country

 OSPF My guard ring

Inter domain anti ring

In domain anti ring

Reissue

effect

Conditions

The rules

To configure

OSPF Routing control

priority ：

[r3-ospf-1]preference 50---- modify OSPF Routing default priority
This command will only affect all types of fields in the routing table OSPF Routing information for .
[r3-ospf-1]preference ase 100---- Modify the default priority of routes imported outside the domain .
The above modification , Only for devices (R3) The default priority of the route in the local route table is
Line modification .

Cost value ：

cost= Reference bandwidth / Real bandwidth
1. 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 . The essence cannot control the route .
2. The 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. 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 .

OSPF The appendix E 

OSPF The road selection principle

Intra domain

  There are multiple passes to reach the same target network segment 1 class ,2 class LSA Learned routing information , The cost value reaching the target network segment will be compared , Choose the one with low cost . The cost value is the same , Then the load will be balanced

Inter domain

  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 .

Outside the country

 

 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

Reissue

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 .

Conditions

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 .

The rules

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 .

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
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