Illustrated network: what is the hot backup router protocol HSRP?

Hello , This is the network technology alliance station .

Today we continue the graphic network series .

Yesterday I introduced to you VRRP Virtual router redundancy protocol .

Today I'd like to introduce to you VRRP Twin brother ：

HSRP

.

HSRP It's a Cisco private agreement , So what are its special functions , What is the principle , and VRRP What is the difference between ？

Today, Rego will take you to study hard , Let's go straight to ！

What is? HSRP？

• English full name ：
  Hot Standby Routing Protocol

• Chinese full name ：
  Hot backup router protocol

• CISCO  Proprietary agreement

• First hop redundancy protocol

• standard ：RFC2281

What is the first hop Redundancy Protocol ？

First hop redundancy protocol ：

• English full name ：
  First Hop Redundancy Protocols

• abbreviation ：
  FHRP

In the network environment , Devices must communicate with each other inside and outside the network , Devices that communicate with other devices outside the network or subnet need a default gateway , The gateway is the default IP Packets are used to ensure that network requests are sent to the correct destination

First route

.

Node configuration used as the default gateway IP Address , Each client in the network or subnet is configured with the same  IP  Address , therefore , If the router or layer 3 switch as the default gateway fails , All devices connected to it will be isolated from the external network .

In order to reduce the occurrence of such failures , Developed

First hop redundancy protocol

 (FHRP).

Let's see if FHRP The situation of ：

There are three first hop redundancy protocols ：

HSRP This article is about ,VRRP We talked about it in the last article ,GLBP In the next section, we will talk about .

HSRP The term

• fictitious  IP
  ： The default gateway address of the virtual device .

• fictitious  MAC  Address
  ：MAC  Address by  HSRP  Automatic generation , front  24  Bit is the default  CISCO  Address , Next 16  Is it HSRP ID, Last  8  Group number with hexadecimal digits .

• priority
  ： By default , The priority value is
  100
  .

• Hello  news
  ： Regular messages exchanged by active and standby routers , These messages every  3  Every second , Tell the status of the router .

• Hold timer
  ： The default value is  10  second , That is, about  hello  Of message value  3  times , This timer tells us the router , If you don't receive it on time , How long will the standby router wait  hello  news .

HSRP  Router role

HSRP  There are three main router roles ：

Main router

The main router is the router through which traffic passes , Provide activity traffic , Actively send and receive data packets to hosts in the region , The primary router is the default gateway router , Only one active router will be selected in the router cluster .

Backup router

If the existing master router is offline , The router in the standby router will be selected as the primary route .

If the main router is offline , Router failover will occur , These changes will not affect the host , The host will remain the same  IP  Address and  MAC  Address , The default gateway  IP  The address is on all hosts

Still the same

, The host  ARP  The table will not change , Because the virtual gateway router  MAC  The address is the same , Failover changes only occur on routers and switches , The host is not affected .

Monitor the router

Monitoring the router is to participate  HSRP  Other routers of the Group .

HSRP  state

Initial

Not ready or unable to participate  HSRP, The protocol is not yet running , Interface available .

Standby

Be a candidate for the next main router , Act as a backup , Monitor and send  hello  news .

Learn

Virtual has not been determined  IP  Address and you haven't seen  hello  news .

Active

Actively forwarding traffic , Receive and forward user traffic .

Listen

Receiving  hello  news .

Speak

Send and receive  hello  news .

Only in three states , Will send  hello  news ：Speak、Standby and Active state .

HSRP  news

HSRP There are three kinds of news ：

Hello news

Hello  Message through

Multicast

swapping , And connect the local router  HSRP  The status and priority values inform other gateways .

Hello  Messages also include groups  ID、HSRP  Timer value 、 Version and authentication information .

Coup news

Coup  The message is that the current standby router wants to assume  HSRP  Sent when the group's primary router role , In other words, when the standby router wants to assume the active role （ preemption ） when , Use coup news .

Resign news

Resign  Messages are sent by the main router at the gateway that is about to shut down or has a higher priority  Hello  or  Coup  When sending a message , This message tells the standby router to be ready and take over the active role .

HSRP  edition

HSRP There are two versions ：

• edition  1

• edition  2

edition  1

• Group number ：
  0 – 255

• fictitious  MAC  Address ：
  0000.0c07.acXX
  （XX =  Group number ）

• Multicast address ：
  224.0.0.2

• Use  UDP  port  1985

edition  2

• Group number ：
  0 – 4095

• fictitious  MAC  Address ：
  0000.0c9f.fXXX
  （XX =  Group number ）

• Multicast address ：
  224.0.0.102

• Use  UDP  port  1985

HSRP Convergence time

HSRP  The convergence time of is determined by

Timer

Definition ,HSRP  The router sends a keep alive message , If there are three  keepalive  The loss of , The router will assume that the main router is turned off , By default , Each of them  3  Seconds to send hello  Data packets , If  10  Not received within seconds  hello（ Retention time ）, Will  active  Expressed as  dead.

HSRP  preemption

Default

Under the circumstances ,HSRP  Device already

Ban

preemption , It means , If devices with higher priority appear in existing  HSRP  On the Internet , It will not automatically become active  HSRP  equipment , Only when both active and standby equipment fail , It will get this role .

If enabled  HSRP  preemption , Then the device with higher priority will declare itself as an activity when it goes online  HSRP  equipment ..

HSRP  Router election

HRSP The main router election is based on

Priority value

（0~255, The default is  100）,

The highest priority

The router of will become the master router .

If the priority is the same ,HSRP  There are

The highest  IP  Address

The router of will become the master router .

summary

HSRP  It is a way to create virtual  IP First hop Redundancy Protocol , yes Cisco  Proprietary agreement , If the primary router fails , The backup router in its network will take over the virtual address .

HSRP There are two versions ：V1  and  V2,V1 The packet is sent to  TTL 1  The multicast address of  

224.0.0.2

, Use  UDP  port

1985

;V2 The packet is sent to  TTL 1  The multicast address of  

224.0.0.102

, Use  UDP  port  

1985

.

This article mainly introduces HSRP The following content ：

• What is? HSRP？

• What is the first hop Redundancy Protocol ？

• HSRP The term

• HSRP  Router role

• Main router

• Backup router

• Monitor the router

• HSRP  state

• Initial

• Standby

• Learn

• Active

• Listen

• Speak

• HSRP  news

• Hello news

• Coup news

• Resign news

• HSRP  edition

• edition  1

• edition  2

• HSRP Convergence time

• HSRP  preemption

• HSRP  Router election

Thank you for reading , If you think the article will help you , Don't forget to like 、 Collection ！ Any questions , Welcome to discuss with me in the comment area below ！！！