Hcip day 14 notes

LDP --- Label distribution agreement --- Mainly used in MPLS The control level of

MPL S The main work to be completed at the control level is to allocate labels and transfer labels . The premise of assigning labels is that labels must first exist in the local routing table , The premise of transferring labels is also to have a routing foundation . therefore ,LDP Want to work properly , You need to IGP As the foundation .

1, Assign tags

Not all devices assign labels to all routing entries in their local routing table , Instead, you decide that you are the outbound station of a certain network segment LSR when , Will actively assign labels .

Of course , In the form of reaching the target network segment LSP In the process , All the middle L SR Need to give the corresponding FEC Assign tags . Then other devices only receive the mapping relationship between the label and the target network segment , Will passively allocate labels . Before assigning labels, you need to complete the check action , Mainly check whether the local routing table of the target network segment can reach , And whether the next hop is the same as the announcer . Labels can be assigned if the inspection is passed , If you fail, you cannot assign labels .

LDP How to assign tags to :

1, In an orderly way --- By default, Huawei devices choose to allocate labels in an orderly manner  

2, Independent way --- There is no need to confirm that you are leaving LSR, You can also actively assign labels to the routing entries in the routing table .

2, Transfer label

Departure LSR After assigning labels , It needs to be passed on to others LSR equipment , The prerequisite for transmission is that they must first LDP Peer relationship . and LDP The prerequisite for establishing peer relationship is to establish LDP conversation .

Local LDP conversation --- A direct connection is established between two devices LDP conversation

long-range LDP conversation --- Between non directly connected devices , You can create remote LDP conversation

LDP The agreement is to establish a local LDP Conversation time , There is no need to manually specify the neighbor IP Address , It can automatically discover neighbor relationships . Mainly because LDP First of all, there will always be multicast (224.0.0.2) Formal period of . Sexual transmission hello Bag to find neighbors .hello Package usage UDP 646 End C To complete .

Local LDP The process of establishing a session :

1, stay LSR. Activate on LDP after , First, send periodically hello Package to complete peer discovery .

stay HELL0 You need to carry a - Some parameters , It contains the transmission address and LDP ID. Transmission address : This address is mainly established later TCP The address needed for the conversation , By default , We will use the L SR ID As this address . So ask for ,LSR ID Must be available and accessible IP Address .

LDP ID: All active LDP Agreed L SR The equipment must have a LDP ID, This ID By 48 Bit binary structure , Expression bit 32 position : 16 position , front 32 Bit usage is LSRID, after 1 6 Bit use 0 To express . This is related to the label space , All device based tag spaces , It's all worth 0.

hello The default sending cycle of packets is 5s, The survival time is 3 times hello Time , Default 15 second

2, Both sides are interacting hello After the package , Will get the other party's transmission address , Will be established according to this transmission address TCP conversation .

In establishment TCP Between sessions ,LDP There are also check actions , You need to confirm the received transmission address first , Is it reachable in the local routing table , Reachable can be established normally TCP conversation .

If both sides establish TCP conversation , Two two-way channels will be created , Waste of resources . At the receiving end hello After the transmission address in the packet , Compare with the local transmission address , The larger the transmission address - Fang , We call it the active party , The active party can take the initiative to establish TCP conversation , The passive side does not establish .

 

 3, complete TCP After the session is established , The larger the delivery address - Party A will give priority to the use of initialization messages , It contains some negotiated parameters and sends them to the passive party . If the other party confirms the parameters , Will reply keeplive Message to confirm , At the same time, send your own local initialization message , Carry your own parameters . The active party will also confirm the parameters after receiving , If there is no problem, it will also be sent keeplive message . Received by both parties keeplive message , It means that the parameter negotiation is successful ,LDP Session successfully established .

after , It also needs to be sent periodically keeplive Keep the message alive , The default sending cycle is 15S, The survival time is 3 Times the cycle sending time , The default is 45 second

Upstream downstream relationship --- It is determined by the flow direction of data layer traffic , The data sender is upstream , The recipient is the downstream . From the perspective of the control layer , Then the direction of label transmission should be from downstream to upstream . Then the upstream equipment will collect the downstream labels .

Label transfer method --- DU Pattern --- Downstream autonomous mode --- Huawei equipment adopts this mode by default , all LSR After assigning labels , You can actively transfer labels to others LSR

If you choose downstream autonomous mode , Then the device passes the label , Unable to judge the relationship between upstream and downstream , The label will be sent to all peer relationships . When the device receives the label , Then you can judge the upstream and downstream relationship based on the routing table . Huawei equipment , Only the upstream equipment will record the labels sent by the downstream equipment , Labels sent by upstream devices will not be saved .( And one more The storage mode of each label is to save both upstream and downstream labels .

DOD Pattern --- Downstream on demand mode --- Only the downstream equipment receives the notification from the upstream equipment , Will send labels to upstream devices .

Data level flow process

In the process of data level traffic passing , Inbound L SR Equipment and battle L SR Both devices need to query two tables , a sheet FIB surface ,- - Zhang LFIB Packets can complete the forwarding process , Resulting in reduced efficiency , Need to optimize .

Optimization idea :

Inbound LSR -- Because the inbound packet does not contain labels , therefore , Must view FIB surface . You can directly add the outbound label to FIB In the table , In this way, you will no longer need to view LFPB surface .

Departure LSR --- PHP --- Last hop pop-up mechanism ---- Departure L SR The equipment is giving FEC Assign special labels directly when assigning labels 3 ( Implicit empty tag ), after , Pass this tag to your upstream device , The upstream will record this tag as an outbound tag in LFIB In the table . When data comes to the device , matching LFIB It was found that the battle tag was 3, Then he will pop up this label directly . Then exit like this L SR The device will receive an unlabeled packet , Then he can directly check FIB Table to realize forwarding .

Huawei devices enable the next last hop pop-up mechanism by default .

LDP Configuration of

1, First of all LSR. Start the IGP agreement , Ensure the routing foundation

2, To configure MPLS Of LSR ID

[r1]mpls Isr-id 1.1.1.1

3, Activate MPLS and LDP

Global activation

[r1]mpls

Info: Mpls starting, please wait... OK!

[r1]mpls ldp

Interface activation

[r1-GigabitEthernet0/0/0]mpls

[r1-GigabitEthernet0/0/0]mpls ldp

[r1]display mpls Idp peer --- see LDP Peer relationship

[r1]display mpls ldp session --- see LDP conversation

[r4]display mpls Isp --- see LFIB surface

Be careful : Huawei equipment only gives /32 Host routing assignment label , because MPLS It is not mainly used in data forwarding , If there are too many routing entries in the routing table , Will result in too many LSP, Waste of resources .

[r4-mpls]lsp-trigger all -- This command can be given by the device /32 Route assignment label outside the host route

MPLS Solve the routing black hole problem

[r2]route recursive-lookup tunnel --- During recursive route lookup , If there is a tunnel, recursively enter the tunnel

[r2]display fib verbose --- see FIB Details of the table

PE --- Service provider boundary equipment

Connection required CE ( Boundary devices of customer network ) equipment , You need to accept the routing information of the customer's private network . He also needs to transmit the routing information of the private network to the remote PE equipment . On . The transmission of this part of the route mainly uses BGP Protocol to deliver . Then the middle P equipment ( Service provider's equipment ), Only need to complete the high-speed forwarding of routing information .

VRF --- Virtual routing forwarding

VPN instance (VPN example ) --- We can abstract a real physical device into several virtual devices . Every virtual device is called a VRF Space , Every VRF Each space has its own routing table ,FIB surface , Dynamic routing protocol , And interface .

 

RD value --- Routing discrimination code

from 64 Bit binary , The most common expression of Huawei equipment is AS:NN ( front AS Representative's AS Number , Back NN Represents a custom value )

 

VPNV4 route

IPV4 Add RD The value of , From the original 32 A into 96 position , It will become VPNV4 route .

MP-BGP

It can carry the routing information of various address groups . If you need to deliver VPNV4 route , You need to use MP- BGP To deliver .

RT--- Routing target value

VPN Target --- 32 Bit binary structure --- from BGP Community attributes to carry

Departure RT value --- Export RT --- PE The equipment is different VRF Outbound with different space configurations RT, Sent by the community attribute , Need and remote PE Inbound on device RT Corresponding .

Inbound RT value --- Import RT --- PE The equipment is different VRF Inbound with different space configurations RT, Compare according to the value carried in the community attribute , Put it in the corresponding VRF In space

Data layer traffic --- Data layer traffic mainly arrives at the far end PE When on the device, you can't tell which one is added VRF In the space , therefore , You need to use double-layer labels to distinguish .---- Outer label ( Close to the second floor ) --- Public label --- from LDP Agreement to allocate , Its purpose is to ensure that the data can pass normally MPLS Domain , Reach the far end PE.

Inner label ( Close to the third floor ) --- Private label --- from MP- BGP Agreement to allocate , The purpose is at the far end PE After the outer label pops up on the device , You can judge which one to reach according to the inner label VRF Of data traffic . The inner label needs to match VRF There is correspondence in space , This label is made up of MP- BGP After the distribution , The community attribute is passed along with the route to the opposite end PE.