Layer 3 switching and VRRP

Catalog

Preface

One . Three layer exchange

Two . Working principle of three-layer switching

3、 ... and .vrrp The role of

Four .vrrp working process

5、 ... and .vrrp To configure

  summary

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Preface

Virtual routing redundancy protocol (Virtual Router Redundancy Protocol, abbreviation VRRP) By IETF A routing protocol is proposed to solve the single point of failure of static gateway in LAN ,1998 The official has been launched in RFC2338 Protocol standard .VRRP It is widely used in edge networks , It is designed to support specific situations IP Data traffic failure transfer will not cause confusion , Allow the host to use a single router , And maintaining the connectivity between routers even when the actual first hop router fails to use .

One . Three layer exchange

Three layer exchange ： Layer 2 switching and layer 3 forwarding

Contains two information tables

Forwarding information table （FIB）：FIB Similar to routing table , Contains the image of the forwarding information in the routing table . When the topology of the network changes , The routing table will be updated , and FIB Will also change .
Adjacency table ： Every FIB entry , The adjacency relation table contains the corresponding number 2 Floor address .

Two . Working principle of three-layer switching

 

PC1 to pc2 Send unicast packets
Switch lookup FIB surface , Find the next hop address
Find the two-layer encapsulation information of the collar relationship corresponding to an address
Forward data

3、 ... and .vrrp The role of

Virtual router redundancy protocol （VRRP） It's a choice protocol , It can dynamically assign the responsibility of a virtual router to VRRP One of the routers . Control the virtual router IP Address of the VRRP A router is called a master router , It's responsible for forwarding packets to these virtual IP Address . Once the main router is not available , This selection process provides a dynamic fail over mechanism , This allows the virtual router to IP The address can be used as the default first hop router of the terminal host . Use VRRP The advantage is that it has higher availability of default path without configuring dynamic routing or route discovery protocol on each end host . VRRP The bag is enclosed in IP Send... In package .

Four .vrrp working process

 1. VRRP The devices in the group elect Master.Master The device sends ARP message , Virtual MAC Address notification to the device or host to which it is connected .

2. Master Periodically, the device sends data to all Backup Device send VRRP Notification message .

3. If Master The device is out of order ,VRRP In the backup group Backup Equipment re elects new Master.

4. primary Master When the equipment fails to recover , If the equipment IP The address is larger than the preempted master, It will be decided to re elect master.

5、 ... and .vrrp To configure

 

SW1
undo t m
system-view
user-interface console 0
idle-timeout 0
q
vlan b 10 20
int e0/0/1
port link-type access
port default vlan 10
int e0/0/2
port link-type access 
port default vlan 20
int g0/0/1
port link-type trunk 
port trunk allow-pass vlan all 
int g0/0/2
port link-type trunk     
port trunk allow-pass vlan all 
q

SW2
undo t m
system-view
user-interface console 0
idle-timeout 0
q
vlan b 10 20 30
int g0/0/1
port link-type trunk 
port trunk allow-pass vlan all 
q
int vlan 10
ip add 192.168.10.100 24
vrrp vrid 1 virtual-ip 192.168.10.1
vrrp vrid 1 preempt-mode timer delay 6
vrrp vrid 1 priority 105
vrrp vrid 1 track int g0/0/2
int vlan 20
ip add 192.168.20.100 24
vrrp vrid 2 virtual-ip 192.168.20.1
vrrp vrid 2 track int g0/0/2
int g0/0/2
port link-type access
port default vlan 30
int vlan 30
ip add 192.168.30.1 24
q

LSW3
undo t m
system-view
user-interface console 0
idle-timeout 0
q
vlan b 10 20 30
int g0/0/1
port link-type trunk 
port trunk allow-pass vlan all 
q
int vlan 10
ip add 192.168.10.110 24
vrrp vrid 1 virtual-ip 192.168.10.1
vrrp vrid 1 track int g0/0/2
int vlan 20
ip add 192.168.20.110 24
vrrp vrid 2 virtual-ip 192.168.20.1
vrrp vrid 2 preempt-mode timer delay 6
vrrp vrid 2 priority 105
vrrp vrid 2 track int g0/0/2
int g0/0/2
port link-type access
port default vlan 30
int vlan 30
ip add 192.168.40.1 24
q

R1
undo t m
system-view
user-interface console 0
idle-timeout 0
q
int g0/0/0
ip add 192.168.30.2 24
int g0/0/1
ip add 192.168.40.2 24
int lo0
ip add 30.0.0.1 24
q
ip route-static 192.168.10.0 24 192.168.30.1
ip route-static 192.168.10.0 24 192.168.40.1 preference 70 
ip route-static 192.168.20.0 24 192.168.30.1
ip route-static 192.168.20.0 24 192.168.40.1 preference 70 

  Cut off the sw2, Check whether it is preempted by the backup route

 

 ​​​​​​​ summary

Three layer routing , One time routing , Forward many times

vrrp Realize one active and multiple standby , To solve a single point of failure

By identifying priorities and ip, The big ones will be called master