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ThinkMo EDU Share – network 55.FHRP – HSRP and VRRP

Jacky.K No Comments 11/18/2022

ThinkMo EDU Share – network 55.FHRP – HSRP and VRRP


  1. HSRP defines a router’s backup group .
  2. The backup group is a group of routers participating in HSRP, and together they simulate a virtual router.
  3. The HSRP standby group contains the following entities:

Active router (active).

Backup router (standby).

Virtual router (Virtual).

other HSRP member routers.

  1. The active router backup router sends Hell. The packets are sent through the multicast destination UDP=1985 port is used, and the interval is 3s.


HSRP: Hot Standby Router Protocol (HSRP: Hot Standby Router Protocol).

The condition for realizing HSRP is that there are multiple routers in the system, and they form a “hot standby group”, and this group forms a virtual router. At any moment, only one router in a group is active, and it forwards data packets. If the active router fails, a backup router will be selected to replace the active router. However, from the perspective of the hosts in this network, the virtual The router has not changed.

Therefore, the host remains connected and is not affected by the failure, thus better solving the problem of router switching.

In order to reduce the data traffic of the network, after the active router and the backup router are configured, only the active router and the backup router send HSRP packets regularly.

If the active router fails, the backup router will take over as the active router. If the backup router fails or becomes the active router, another router will be elected as the backup router.

  • Features:
  1. High reliability . The HSRP (Hot Backup Redundancy Protocol) protocol is used between the two routers to ensure that any one of the two routers goes down, or the WAN port of the router goes down, it will quickly switch to the other one .
  2. Effectively achieve load balancing, make full use of bandwidth resources, and achieve load balancing.
  3. There is no single point of failure problem.

HSRP commands

Core-switch(config-if)#standby 1 ip

Add the interface to HSRP group 1, and the virtual IP is

Core-switch(config-if)#standby 1 priority 120

The priority of this interface in group 1 is 120

Core-switch(config-if)#standby 1 preempt

When the priority of active is lower than this interface, preempt active (preemption is disabled by default)

Core-switch#show standby brief Verify the working status of HSRP

Experiment 1:

Requirements: R1 and R2 do routing redundancy.

Basic ip configuration:

LSP1 is the same as LSP2:


LSP1(config-if)#ip add

LSP1(config-if)#no shutdown



PC1(config)#no ip routing

PC1(config)#int f0/0

PC1(config-if)#ip add

PC1(config-if)#no shutdown


PC1(config)#ip default-gateway

R1 is the same as R2:

R2(config)#int f0/0

R2(config-if)#ip add

R2(config-if)#no shutdown


R2(config)#int f0/1

R2(config-if)#ip add

R2(config-if)#no shutdown

R2#ping to ensure that the direct network is pinged normally


· Configure HSRP:

R1 is configured the same as R2:

R2(config)#int f0/1

R2(config-if)#standby 1 ip

R2(config-if)#standby 1 preempt Turn on the preemption function, and the one with higher priority will become the main route first


R1#show standby br Check whether the configuration is complete

Interface Grp Prio PState Active Standby Virtual IP

Fa0/1 1 100 P Active local

R2#show standby brief

Interface Grp Prio P State Active Standby Virtual IP

Fa0/1 1 100 P Standby local

lsp1 route:

LSP1(config)#ip route f0/0

Use pc1 to test whether the ping is successful


Test whether the R1 port is down and will switch to R2

PC1#ping repeat 200

Type escape sequence to abort.

Sending 200, 100-byte ICMP Echos to, timeout is 2 seconds:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!

Success rate is 97 percent (194/200), round-trip min/avg/max = 104/172/320 ms

R1(config)#int f0/1


Remarks: R1(config-if)#standby 1 priority 120, set the priority, and adjust the main route manually.

show arp, used to view the cached ip and corresponding mac:

The last 01 of the mac address corresponding to the virtual route in the figure above indicates that the group number is 1. The last two digits are hexadecimal characters.

Important: HSRP has a disadvantage that it cannot sense uplink damage. For example, in the previous topology diagram, the failure of LSP1 or 2 will not trigger standby redundancy, so you need to use the associated Track:

R1(config-if)#standby 1 track f0/0 50, monitor whether the f0/0 protocol is down on the f0/1 port. If it is down, the priority of the f0/1 port is lowered by 50.

TIPS: Port preemption must be enabled.

HSRP load idea: establish different groups and serve as backups for each other.


  • Introduction

Using VRRP a group of routers work together, but only one is active. Multiple routers in a VRRP group share a virtual IP address, which is used as the default gateway address of all hosts in the LAN. The VRRP protocol determines which router is activated, and the activated router is responsible for receiving and routing the data packets sent.

  • VRRP router type
  1. Master router:

It is the router that actually forwards data packets in the VRRP group. In each VRRP group, only the MASTER responds to the ARP request for the virtual IP address.

  1. Backup router:

It is the router in the listening state in the VRRP group. Once the Master router fails, the BACKUP router will start to take over.

  • Three states of VRRP
  1. Initial state (Initialize):

The router enters this state when it is just started, and enters other states after exchanging data through VRRP packets.

  1. Active status (Master):

A state of currently forwarding data packets determined by routers in a VRRP group through VRRP packet exchange.

  1. Backup status (Backup):

The routers in the VRRP group are in the monitoring state determined by VRRP packet exchange.

  • VRRP packets

VRRP routers use multicast for message transmission. The IP multicast address used by VRRP packets is

  • Notification interval
  1. The master router sends VRRP advertisement messages according to the time interval defined by Advertisement_Interval, which is 1s by default.
  2. It can be manually configured on the backup router but must be the same as the main router, and this time interval can also be learned from the main router.
  • Hold time

The interval at which the Backup router considers the Master router to be down.

By default, it is equal to three times the interval for sending VRRP Advertisement packets.

  • VRRP configuration

VRRP and HSRP configurations are basically the same

R1(config-if)#vrrp1 ip Add the interface to group 1, the virtual ip is

R1(config-if)#vrrp1 priority 120 Set the priority of the interface in group 1

R1(config-if)#vrrp1 preempt Enable preemption function, enabled by default

The difference is track tracking:

Gateway(config)#track 1 interface f0/0 line-protocol Create a tracking object 1 in global mode to track the f0/0 link protocol

Gateway(config-if)#vrrp 1 track 1 decrement 30 If the condition of track1 is met, subtract 30 from the priority of vrrp1 where the current interface is located

Gateway(config-if)#vrrp 1 authentication md5 key-string lance This is encryption, whether it needs to depend on the situation

The difference between HSRP and VRRP

HSRP is private to CISCO, and VRRP is a public protocol.

VRRP allows physical IP to overlap with virtual IP (become MASTER), but HSRP does not.

By default, preemption is enabled for VRRP, but not for HSRP.

HSRP sends packets with multicast; virtual mac format: 0000.0c07.ac group ID.

VRRP is sent in multicast; 000.5e00.01 group ID.

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