HSRP Configuration on Cisco IOS
In this section we will do an HSRP configuration to understand the issue better. To do this wewill use the below topology. At the end of this article, you will find the GNS3 configuration lab of this lesson.
Before the HSRP configuration, we must prepare our topology. WE will change the router names and we will assigned the ip addresses of the router interfaces.
For the left side of the topology, we will use 10.10.10.0 network and for the right side, we will use 10.10.20.0 network. All the interfaces connected to the layer 2 swicth will be assigned with the ip addresses related to its connected port. For example the fa0/0 interface of the Site1 router will be assigned the ip address 10.10.10.1 and the GW1’s and GW2’s fa0/0 ip addresses will be 10.10.10.2 and 10.10.10.3 orderly.
After interface configuration, we will configure a static route on each Site1 and Site2. In this static route we will use two virtual ip addresses that we will explain in this article. This virtual addresses will be 10.10.10.10 and 10.10.20.20.
Now our configuration is ready to HSRP configuration. Let’s start on one side(left) on GW1 and GW2 and after that we will configure a second HSRP configuration for the other side(right).
You do not need to do this configuration for both sides, but in this configuration, we do it for both sites. After this you can check the configuration with “show standby” command on GW1 and GW2. As you see below, for both redundancy configuration GW1 is the active router and the GW2 is the standby.
To check that the traffic from Site1 to Site2 is prefering the GW1 while it is active, do traceroute from Site1. AS you see below the next hop will be the GW1.
And like the same, when you start traceroute from Site2 to Site1, the traffic will choose the GW1 again, because for this redundancy session, the active router is GW1 again.
When we administratively shutdown the fastethernet 0/0 interface of GW1 for test, we see that GW2 become active by a console message and after that when we check the status, we see that it is active like below.
Lastly, when we start traceroute from Site1 to Site2 then we realize that the traffic is no longer go through GW1, but it is going through GW2.
Beside this basic configuration commands, we can also use the below command while configuring the redundancy with HSRP.
We use “preempt” command above but it is necessary to tell about something about this command. This command is used to force a router that has higher friority become active router. By default if a higher priority router come online, it does not become active if the preempt command is not used on it.
Another important point is “delay” command. It is use to mentione the waiting time before becoming active router.
You can also change hello and holder time with the below command.
By default HSRP Hello packets are sent to the multicast address 220.127.116.11 over UDP port 1985.
There can be multiple HSRP virtual ip addresses.
HSRP Group is also assigned a “virtual MAC address”. For HSRP Group 8, the value is 0000.0c07.ac08.
For authentication, all the HSRP group must be configured with the same password.
Lastly I want to refer one point, “tracking”. During HSRP usage, there can be a problem on an interface that is critical for the connection. This interface can be other than the interface that provide standby-active routers’ connection. So, a link down in this interface can not be realize by stanby router. To overcome this issues, HSRP use “track” command that provide decreasing the priority of the router even if a specified interface become down. With this decrease, the active router is changed.
I hope this artickle will be helpful for you. Let’s continue with VRRP, the standard based redundancy protocol;)
Other First Hop Redundancy Protocols (FHRPs) Lessons
First Hop Redundancy Protocols (FHRPs) – Overview
First Hop Redundancy Protocols (FHRPs) – HSRP
First Hop Redundancy Protocols (FHRPs) – HSRP Configuration on Cisco
First Hop Redundancy Protocols (FHRPs) – VRRP
First Hop Redundancy Protocols (FHRPs) – VRRP Configuration on Cisco
First Hop Redundancy Protocols (FHRPs) – GLBP
First Hop Redundancy Protocols (FHRPs) – GLBP Configuration on Cisco