This tutorial explains how to configure, verify, and debug the HSRP protocol on a Cisco router. Learn how to configure HSRP load balancing through a packet tracer example.
HSRP (Hot Standby Router Protocol) is a Cisco proprietary protocol. It is used to dynamically manage multiple default gateway routers. It creates a group and adds all available gateway routers to that group. Afterward, it selects two routers: one as the main (or active) router and the other as the standby (or passive) router. The main router forwards the traffic. The standby router waits for the main router to fail. If the main router fails, the standby router takes over the responsibilities of the main router. If the standby router fails, one router from the remaining routers takes over the responsibilities of the standby router.
To learn this concept in detail, you can check the previous part of this article. The previous part of the tutorial is the following.
The major drawback of this concept is that it does not utilize all routers effectively. At a time, it uses only one router and keeps all remaining routers in the standby position. For example, if you have ten gateway routers, at a time it will use only one router and will keep the remaining nine routers in the waiting or standby position.
We can't change the basic concept of the HSRP. But we can design our network in such a way that it allows us to configure multiple instances of HSRP. Through multiple instances of HSRP, we can utilize all routers at a time. This is known as HSRP load balancing.
In the following section, we will learn how to do this through an example. First, we will create an example network on Packet Tracer. Then, we will configure the HSRP protocol and HSRP load balancing on it. Later, we will discuss how to debug and verify the HSRP configuration.
HSRP Packet Tracer lab
Either create a Packet Tracer lab as shown in the following picture or download the following pre-created lab.
Packet Tracer lab example network layout
In this example network, the local subnet contains end-user systems and the remote subnet contains a Server. The local subnet is connected to the remote subnet via WAN links. For redundancy, three gateway routers (R1, R2, and R3) are used to connect the local subnet to the remote subnet.
To dynamically manage gateway routers, if we configure HSRP on gateway routers, only one router will be used at a time. To use all routers at the same time, we need to configure multiple instances of HSRP. To configure multiple instances of HSRP, we need to divide the network into sub-networks. After dividing the network into sub-networks, we can configure a separate instance of HSRP on each sub-network.
Our example network contains three gateway routers. To use three gateway routers at the same time, we need to configure three instances of HSRP. To configure three instances of HSRP, we need to divide the network into three sub-networks. To divide the network, we can use VLANs. VLANs divide a network into sub-networks.
VLANs are logical. To implement VLANs in the network, we don't need to modify the physical layout of the network. A VLAN creates a logical boundary. Devices inside the boundary can't access the devices that are outside the boundary. In simple words, devices inside a VLAN and devices outside the VLAN belong to two separate networks and can't communicate without a router.
In our example, we can divide our local subnet into three VLANs and can configure a separate instance of HSRP in each VLAN. Since the HSRP load balancing depends on VLAN, if you don't know what VLANs are, I strongly suggest you take a pause here and learn VLANs first.
To learn how VLANs work and how to configure VLANs in the network, you can use the following article.
Initial configuration
The initial configuration allows us to verify, test, and debug the HSRP configuration. The initial configuration includes the following settings.
- IP configuration on all interfaces
- The same routing protocol on all routers
- The same VLANs database on all switches
- VLANs configuration on all interfaces that are connected to the local subnet
- DTP configuration on all interfaces that carry data of multiple VLANs
- Router-on-stick configuration on the interface that provides connectivity between multiple VLANs
The following image shows the initial configuration of our example network.
Either download the following pre-configured lab or configure the initial configuration as described in the following section.
HSRP Packet Tracer lab with the initial configuration
Configuring the initial configuration
This section describes how to configure the initial configuration on our example network. If you are using the pre-configured lab, skip this section. The pre-configured lab already contains this initial configuration.
R1
R1>enable R1#configure terminal R1(config)#interface Serial0/0/0 R1(config-if)#ip address 40.0.0.1 255.0.0.0 R1(config-if)#no shutdown R1(config-if)#exit R1(config)#interface gigabitEthernet 0/0 R1(config-if)#no ip address R1(config-if)#no shutdown R1(config-if)#exit R1(config)#interface gigabitEthernet 0/0.10 R1(config-subif)#encapsulation dot1Q 10 R1(config-subif)#ip address 10.0.0.1 255.0.0.0 R1(config-subif)#exit R1(config)#interface gigabitEthernet 0/0.20 R1(config-subif)#encapsulation dot1Q 20 R1(config-subif)#ip address 20.0.0.1 255.0.0.0 R1(config-subif)#exit R1(config)#interface gigabitEthernet 0/0.30 R1(config-subif)#encapsulation dot1Q 30 R1(config-subif)#ip address 30.0.0.1 255.0.0.0 R1(config-subif)#exit R1(config)#router rip R1(config-router)#network 10.0.0.0 R1(config-router)#network 20.0.0.0 R1(config-router)#network 30.0.0.0 R1(config-router)#network 40.0.0.0 R1(config-router)# exit R1(config)#
R2
R2>enable R2#configure terminal R2(config)#interface Serial0/0/0 R2(config-if)#ip address 50.0.0.1 255.0.0.0 R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface gigabitEthernet 0/0 R2(config-if)#no ip address R2(config-if)#no shutdown R2(config-if)#exit R2(config)#interface gigabitEthernet 0/0.10 R2(config-subif)#encapsulation dot1Q 10 R2(config-subif)#ip address 10.0.0.2 255.0.0.0 R2(config-subif)#exit R2(config)#interface gigabitEthernet 0/0.20 R2(config-subif)#encapsulation dot1Q 20 R2(config-subif)#ip address 20.0.0.2 255.0.0.0 R2(config-subif)#exit R2(config)#interface gigabitEthernet 0/0.30 R2(config-subif)#encapsulation dot1Q 30 R2(config-subif)#ip address 30.0.0.2 255.0.0.0 R2(config-subif)#exit R2(config)#router rip R2(config-router)#network 10.0.0.0 R2(config-router)#network 20.0.0.0 R2(config-router)#network 30.0.0.0 R2(config-router)#network 50.0.0.0 R2(config-router)# exit
R3
R3>enable R3#configure terminal R3(config)#interface Serial0/0/0 R3(config-if)#ip address 60.0.0.1 255.0.0.0 R3(config-if)#no shutdown R3(config-if)#exit R3(config)#interface gigabitEthernet 0/0 R3(config-if)#no ip address R3(config-if)#no shutdown R3(config-if)#exit R3(config)#interface gigabitEthernet 0/0.10 R3(config-subif)#encapsulation dot1Q 10 R3(config-subif)#ip address 10.0.0.3 255.0.0.0 R3(config-subif)#exit R3(config)#interface gigabitEthernet 0/0.20 R3(config-subif)#encapsulation dot1Q 20 R3(config-subif)#ip address 20.0.0.3 255.0.0.0 R3(config-subif)#exit R3(config)#interface gigabitEthernet 0/0.30 R3(config-subif)#encapsulation dot1Q 30 R3(config-subif)#ip address 30.0.0.3 255.0.0.0 R3(config-subif)#exit R3(config)#router rip R3(config-router)#network 10.0.0.0 R3(config-router)#network 20.0.0.0 R3(config-router)#network 30.0.0.0 R3(config-router)#network 60.0.0.0 R3(config-router)# exit R3(config)#
RemoteRouter(RR)
Router>enable Router#configure terminal Router(config)#interface Serial0/0/0 Router(config-if)#ip address 40.0.0.2 255.0.0.0 Router(config-if)#no shutdown Router(config-if)#exit Router(config)#interface Serial0/0/1 Router(config-if)#ip address 50.0.0.2 255.0.0.0 Router(config-if)#no shutdown Router(config-if)#exit Router(config)#interface Serial0/1/0 Router(config-if)#ip address 60.0.0.2 255.0.0.0 Router(config-if)#no shutdown Router(config-if)#exit Router(config)#interface GigabitEthernet0/0 Router(config-if)#ip address 70.0.0.1 255.0.0.0 Router(config-if)#no shutdown Router(config-if)# Router(config-if)#exit Router(config)#router rip Router(config-router)#network 70.0.0.0 Router(config-router)#network 60.0.0.0 Router(config-router)#network 50.0.0.0 Router(config-router)#network 40.0.0.0 Router(config-router)# exit Router(config)#
VLAN and DTP configuration
Switch1
S1>enable S1#configure terminal S1(config)#vlan 10 S1(config-vlan)#exit S1(config)#vlan 20 S1(config-vlan)#exit S1(config)#vlan 30 S1(config-vlan)#exit S1(config)#interface fastEthernet 0/1 S1(config-if)#switchport access vlan 10 S1(config-if)#exit S1(config)#interface fastEthernet 0/2 S1(config-if)#switchport access vlan 20 S1(config-if)#exit S1(config)#interface fastEthernet 0/3 S1(config-if)#switchport access vlan 30 S1(config-if)#exit S1(config)#interface gigabitEthernet 0/1 S1(config-if)#switchport mode trunk S1(config-if)#exit S1(config)#interface fastEthernet 0/24 S1(config-if)#switchport mode trunk S1(config-if)#exit S1(config)#interface fastEthernet 0/23 S1(config-if)#switchport mode trunk S1(config-if)#exit S1(config)#
Switch2
S2>enable S2#configure terminal S2(config)#vlan 10 S2(config-vlan)#exit S2(config)#vlan 20 S2(config-vlan)#exit S2(config)#vlan 30 S2(config-vlan)#exit S2(config)#interface fastethernet 0/1 S2(config-if)#switchport access vlan 10 S2(config-if)#exit S2(config)#interface fastethernet 0/2 S2(config-if)#switchport access vlan 20 S2(config-if)#exit S2(config)#interface fastethernet 0/3 S2(config-if)#switchport access vlan 30 S2(config-vlan)#exit S2(config)#interface gigabitEthernet 0/1 S2(config-if)#switchport mode trunk S2(config-if)#exit S2(config)#interface fastEthernet 0/24 S2(config-if)#switchport mode trunk S2(config-if)#exit S2(config)#interface fastEthernet 0/23 S2(config-if)#switchport mode trunk S2(config-if)#exit S2(config)#interface fastEthernet 0/22 S2(config-if)#switchport mode trunk S2(config-if)#exit S2(config)#interface fastEthernet 0/21 S2(config-if)#switchport mode trunk S2(config-if)#exit S2(config)#
Switch3
S3>enable S3#configure terminal S3(config)#vlan 10 S3(config-vlan)#exit S3(config)#vlan 20 S3(config-vlan)#exit S3(config)#vlan 30 S3(config-vlan)#exit S3(config)#interface fastEthernet 0/1 S3(config-if)#switchport access vlan 10 S3(config-if)#exit S3(config)#interface fastEthernet 0/2 S3(config-if)#switchport access vlan 20 S3(config-if)#exit S3(config)#interface fastEthernet 0/3 S3(config-if)#switchport access vlan 30 S3(config-if)#exit S3(config)#interface gigabitEthernet 0/1 S3(config-if)#switchport mode trunk S3(config-if)#exit S3(config)#interface fastEthernet 0/21 S3(config-if)#switchport mode trunk S3(config-if)#exit S3(config)#interface fastEthernet 0/22 S3(config-if)#switchport mode trunk S3(config-if)#exit S3(config)#
The IP configuration of the Server0
Implementing the HSRP protocol
The configuration of HSRP is straightforward. To configure HSRP, you need the following command.
#standby HSRP_Group_Number ip Virtual_IP_Address
In this command, the HSRP_Group_Number is the group number of HSRP and the Virtual_IP_address is the virtual IP address of the HSRP group. You need to run this command on all interfaces that you want to use as the default gateway for a particular sub-network (or a VLAN).
In our example, we divided the local network into the three VLANs (sub-networks): VLAN10, VLAN20, and VLAN30. The following table lists the group ID (HSRP group number) and group IP (HSRP virtual IP) for these VLANs.
| VLAN | Router | Interface | Interface IP | HSRP Group | HSRP IP |
| 10 | R1 | G0/0.10 | 10.0.0.1 | 10 | 10.0.0.10 |
| 10 | R2 | G0/0.10 | 10.0.0.2 | 10 | 10.0.0.10 |
| 10 | R3 | G0/0.10 | 10.0.0.3 | 10 | 10.0.0.10 |
| 20 | R1 | G0/0.20 | 20.0.0.1 | 20 | 20.0.0.10 |
| 20 | R2 | G0/0.20 | 20.0.0.2 | 20 | 20.0.0.10 |
| 20 | R3 | G0/0.20 | 20.0.0.3 | 20 | 20.0.0.10 |
| 30 | R1 | G0/0.30 | 30.0.0.1 | 30 | 30.0.0.10 |
| 30 | R2 | G0/0.30 | 30.0.0.2 | 30 | 30.0.0.10 |
| 30 | R3 | G0/0.30 | 30.0.0.3 | 30 | 30.0.0.10 |
If you only want to implement HSRP, the above command and configuration are sufficient. You don't any further configuration. But, with this configuration, only one router will active at a time. If you want to make all routers active at the same time, you need to configure HSRP load balancing.
Configuring the HSRP load balancing
By default, HSRP sets a router as the main router if it comes up first. For example, if you have three routers in an HSRP group. The router that starts first will be selected as the main router. Once the main router is selected, HSRP does not run the selection process again until the main router remains available.
To configure HSRP load balancing, we have to adjust the priority sequence in such a way that if a router is active in one VLAN, it does not become active in other VLANs. We also need to make sure that HSRP always uses our sequence, no matter which router starts first.
To set priority in this way, we need the following commands.
#stanby HSRP_Group_ID priority Priority_Sequence #stanby HSRP_Group_ID preempt
The first command sets the priority of the interface (router) in the HSRP group. You can set any value in the range 0 - 255. The default value is 100. If you will not use this command, HSRP will assign the default priority to the interface. HSRP selects the interface that has the highest value. For example, if two interfaces have priority values 120 and 140, the interface that has the priority value 140 will be selected.
The second command instructs HSRP to always use our sequence, no matter which router is started earlier or later. You need to run this command only on the interface that you want to make active for the VLAN.
The following table lists the priority values that we will use in our example network.
| VLAN | Router | Interface | Priority | Preempt |
| 10 | R1 | G0/0.10 | 120 | yes |
| 10 | R2 | G0/0.10 | 100 (default) | |
| 10 | R3 | G0/0.10 | 110 | |
| 20 | R1 | G0/0.20 | 110 | |
| 20 | R2 | G0/0.20 | 120 | yes |
| 20 | R3 | G0/0.20 | 100 (default) | |
| 30 | R1 | G0/0.30 | 100 (default) | |
| 30 | R2 | G0/0.30 | 110 | |
| 30 | R3 | G0/0.30 | 120 | yes |
Let's configure the HSRP load balancing on our example network.
R1
R1>enable R1#configure terminal R1(config)#interface gigabitEthernet 0/0.10 R1(config-subif)#standby 10 ip 10.0.0.10 R1(config-subif)#standby 10 priority 120 R1(config-subif)#standby 10 preempt R1(config-subif)#exit R1(config)#interface gigabitEthernet 0/0.20 R1(config-subif)#standby 20 ip 20.0.0.10 R1(config-subif)#standby 20 priority 110 R1(config-subif)#exit R1(config)#interface gigabitEthernet 0/0.30 R1(config-subif)#standby 30 ip 30.0.0.10 R1(config-subif)#exit R1(config)#
R2
R2>enable R2#configure terminal R2(config)#interface gigabitEthernet 0/0.10 R2(config-subif)#standby 10 ip 10.0.0.10 R2(config-subif)#exit R2(config)#interface gigabitEthernet 0/0.20 R2(config-subif)#standby 20 ip 20.0.0.10 R2(config-subif)#standby 20 priority 120 R2(config-subif)#standby 20 preempt R2(config-subif)#exit R2(config)#interface gigabitEthernet 0/0.30 R2(config-subif)#standby 30 ip 30.0.0.10 R2(config-subif)#standby 30 priority 110 R2(config-subif)#exit R2(config)#
R3
R3>enable R3#configure terminal R3(config)#interface gigabitEthernet 0/0.10 R3(config-subif)#standby 10 ip 10.0.0.10 R3(config-subif)#standby 10 priority 110 R3(config-subif)#exit R3(config)#interface gigabitEthernet 0/0.20 R3(config-subif)#standby 20 ip 20.0.0.10 R3(config-subif)#exit R3(config)#interface gigabitEthernet 0/0.30 R3(config-subif)#standby 30 ip 30.0.0.10 R3(config-subif)#standby 30 priority 120 R3(config-subif)#standby 30 preempt R3(config-subif)#exit R3(config)#
We also need to configure or update IP configuration on PCs of the local subnet to use the virtual IP address of the HSRP group as the default gateway. The following table lists the IP configuration of all PCs.
| PC | VLAN | HSRP Group | IP Address | Subnet mask | Gateway IP |
| V10PC1 | 10 | 10 | 10.0.0.100 | 255.0.0.0 | 10.0.0.10 |
| V20PC1 | 10 | 10 | 10.0.0.101 | 255.0.0.0 | 10.0.0.10 |
| V30PC1 | 10 | 10 | 10.0.0.102 | 255.0.0.0 | 10.0.0.10 |
| V20PC1 | 20 | 20 | 20.0.0.100 | 255.0.0.0 | 20.0.0.10 |
| V20PC2 | 20 | 20 | 20.0.0.101 | 255.0.0.0 | 20.0.0.10 |
| V20PC3 | 20 | 20 | 20.0.0.102 | 255.0.0.0 | 20.0.0.10 |
| V30PC1 | 20 | 30 | 30.0.0.100 | 255.0.0.0 | 30.0.0.10 |
| V30PC2 | 20 | 30 | 30.0.0.101 | 255.0.0.0 | 30.0.0.10 |
| V30PC3 | 20 | 30 | 30.0.0.102 | 255.0.0.0 | 30.0.0.10 |
Assign IP configuration on all PCs as listed in the above table. The following image shows the IP configuration on V10PC1.
Testing and verifying HSRP load balancing
To test and verify the HSRP configuration, we can use the "ping" and "tracert" commands.
Open the command prompt of any PC (such as V10PC1) and use the ping command to test connectivity between the PC and Server. Use the tracert command to print the path between the PC and Server. If HSRP is configured properly, the main gateway router should be used to forward the packet.
Now, power off the switch's interface that connects the PC to the default gateway router.
Wait for a few seconds, and run both commands on the PC again. If the PC can still access the Server, it verifies that the HSRP configuration is working properly. It also verifies that the failed gateway router has been replaced by the standby router.
Now power on the switch's interface again, wait for a few seconds, and run both commands again. This time the PC should take the original path again. The main gateway router should be the original gateway router again.
You can repeat this process from other PCs to do more testing.
The following link provides the lab used in this tutorial with all configurations. You can use this lab to check your configuration or for any other purpose.
HSRP Packet Tracer lab with all configurations
Debugging and troubleshooting HSRP configuration
If the HSRP configuration does not work, use the following steps to debug and troubleshoot the configuration.
Check the IP configuration of PCs
PCs of the local subnet must be configured to forward traffic to the virtual IP address of the HSRP group. If PCs are configured to forward traffic to the physical interface of the router, the HSRP configuration will not work.
Check the HSRP group ID members
The HSRP group ID must be the same on all members. HSRP uses the group ID to add an interface to the group. If two interfaces are configured with two different group IDs, they will work in two different groups.
Check the virtual IP address on all members
HSRP uses the virtual IP address to receive traffics from the local subnet. If two interfaces of the same HSRP group are configured with different virtual IP addresses, the interface that is configured with the virtual IP that is configured as the default gateway IP on the local subnet will receive the traffic from the local subnet.
You can use the "show standby brief" command to view the standby configuration on the router. The following image shows the output of this command.
The "show standby brief" command provides the summarized version of the configuration. If you want to view the detailed version of the configuration, use the "show standby" command.
That's all for this tutorial. If you like this tutorial, please don't forget to share it with friends through your favorite social network.
