CCNP Part XII BGP (IV)

CCNP- Chapter 12 -BGP( Four )

This time, we will continue to follow the last route selection principle
Last time it was before 6 strip , Now it's the following 7 strip

BGP The default routing principle is 11 strip , It can be configured to go to 13 strip 

7、 ... and .EBGP Routing is better than IBGP

I don't know how to say this
If A-B-C
that A-B by IBGP
B-C by EBGP Words
They also announced an entry
In the case of symmetry on both sides , Will choose EBGP Announced entries

8、 ... and . Disguised reference IGP agreement

It's hard to say why ?
He's like this
If above 7 There is no way to choose
After arriving at this one

IBGP Not effective !

 He will choose the one closest to the machine IGP Routes learned by neighbors 
 So I will compare the metrics of routing protocols at this time 
 Like one side EIGRP On one side OSPF
 One 90 One 110
 Then choose EIGRP over there 
 The smaller the measure, the better 
 But if all routes are static . I can't compare it for so long , I'll compare the following nine 
 Or the same routing protocols on both sides have the same bandwidth , I can't compare it with this one 

Nine . Load balancing ( Apply to EBGP)

If you can't compare with the first eight , If the ninth item is configured with , Load balancing
If you don't configure , It's like this
If the configuration makes it a load balancer
To configure :maximuh-path In fact, theoretically speaking, this is Article 10

From older EBGP Neighbors of , Choose who has a long time
Because the longer it takes , It means the more stable

Ten . Smaller ones are preferred router-id

BGP Of route-id What is it? ?

Choose the largest local lo To act as RID
Follow ospf,eigrp equally
It can be set manually or automatically

BGP Of router-id Generally, it will be manually opened , Because automatic election is easy to conflict
BGP It's not allowed RID Repetitive

The rule of choice is
Whose? route-id Small , Just go who

11、 ... and . Compare neighbor addresses

At this point, it is basically impossible to compare
You can't have the same address as your neighbors ?
The smaller the address, the better

Twelve . Preferred with smaller cluster-list(RR)

What is this thing ?
This thing is called RR
Routing reflectors

What is this routing reflector used for ?
That is, you can send routing entries to other devices

What does that mean ? stay R1 The routing entry sent from
Can pass 2 Pass to 3 and 4

Write directly to his neighbor reoute-reflector-client
Come and have a look at this time R3 and R4 The routing table for


R3 and R4 Received routing entries

If a device acts as a reflector client
Then the items from this device , I will pass it on to others IBGP neighbor
From other IBGP Entries from neighbors , It will also be passed to the client .

 therefore , Just do it RR The client of , So in fact, it is equivalent to breaking IBGP The anti ring mechanism of 

There is no limit to the number of clients

Here it is. originator It's called origin ID, It means who announced , Who started it
This one at the back cluster_list Well It is used to record every machine passing by RR The equipment BGP Of RID
But here his name is Cluster_ID

 So here comes the question , Said so much , What about the anti ring ???
 Don't worry. 
 coming 
 In fact, this route selection rule is similar to EBGP The anti ring is the same 
 It is equivalent to an additional label 

Anti ring rules :
If I receive a message containing my own cluster_list The routing , Then it will be rejected !
So why say RID You must specify... Manually .
This is aimed at RR Anti ring mechanism

RR The core
I received a message IBGP After routing, send it to another IBGP neighbor

This road selection principle
Preferably shorter cluster-list
Actually, I feel like this thing as-path equally
Just change the name
Because you can transmit , Every time you pass a device, it will increase , That's for sure !

Summary

Why use summary ?
Multiple changes 1 strip , Reduce the size of the routing table
But there will be routing black holes , Unless
For example, one of you C paragraph , Announced 254 individual , That's not really necessary , The default route is fine

IBGP Summary method :

After the summary, there is 100.1.0.0/16 Of

The receiving party

EBGP Summary

What can you see
The above is before the summary , The following is the summary
You can see that there are more measurements 0 and as-path Less 100
But what are the disadvantages of this ?

> First of all, it will affect the route selection 
> The second will affect the loop 

< Come and have a look at this time R2 The routing table for >

notice R2 On the right side of the road, there is a S
S In the explanation of routing table, it means inhibition suppressed.

But the problem is
Why would he as-path Reduction ?

 This is because , about R2 Come on , This route is not transmitted by me 
 But I suppressed the following 
 Then I ` To regenerate the ` A message was sent out 
 So for me, it just passed me 
 I'm the only one who sends it out 

therefore

1. When in BGP When summarizing , If not in the originating router 
2. But in the case of the aggregation of routers in the intermediate route 
3. You need to add a parameter 
4. Apply to EBGP,IBGP There is no need for 

This one in this command as-set It means , It is required to keep the original AS Number

 After changing the configuration, look at the routing table of the receiver 

Peer groups (Peer-Group)

In fact, this thing is easy to understand
Like link aggregation
All interfaces receive a command from a group to complete the configuration of all interfaces

First create a group

The information represented respectively is
1. other party as by 100
2. With your own lo The port is the update source
3. do rr Reflector
Done , You have to use it.
How to do? ?

ok Done.
Dolls
Make a plastic shell
Just put a Bing Dwen Dwen in

summary

1.BGP After 7 Principles of selection 
 The seventh .EBGP be better than IBGP
 The eighth . Compare the bottom IGP
 The ninth . Set up load balancing 
 The first ten . Compare time , Choose a longer (EBGP Environmental Science )
 The eleventh . Compare Route-ID( The smaller the better. )
 twelfth . Use RR When , shorter cluster_list
 thirteenth . Compare neighbors IP, The smaller the better. 
2.RR- Routing reflectors ( Apply to IBGP)
 If one IBGP The neighbor of receives the routing entry and transmits it to another neighbor 
RR It's an intermediate device , Equivalent to a reflector 
 The reflection is the routing entry of the client 
 also RR It also has anti ring mechanism ,originator-id/cluster_list
3. Route summary ,EBGP Not the originating router , You need to add as-set
4. Peer groups ,peer-group, Build template configuration .

OK, this time is over , Welcome to my article . I am a CCIE-Yasuo, Just pay attention to me if you like , See you in the next issue .
Welcome the students of Xinmeng education to communicate together , I am a 41 The strong wind and swordsman of the period
At the same time, I am also a 18 It was written at school by a student from a college aged , If there is any mistake or infringement, please contact us in time to delete .