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Now you could configure a PC with 2 default gateways

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in other words set the default gateway to switch 1

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and switch 2 but that doesn’t work very well in windows

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and other operating systems

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so I can go to my local area connection, go to properties

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change the properties for IPv4

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and try and configure multiple default gateways

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but that’s not going to work very well at all.

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So it’s better to set the PC's to use a single default gateway

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which in this case is the HSRP virtual router

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and it’s important to remember that this is a virtual router

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not a physical router it doesn’t actually exist in our topology

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but these PC's will be configured to talk

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to the relevant virtual IP addresses in the same VLAN

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and 1 of the physical switches will forward the traffic

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on behalf of the virtual router.

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That’s once again determined through an election

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the device with the highest priority will become the forwarder for a VLAN.

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So as an example, we'll configure switch 1 with the priority of 200 on VLAN 10

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and switch 2 with the priority of 200 on VLAN 20

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to ensure that switch 1 becomes the active forwarder

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or active router for VLAN 10

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and switch 2 becomes the active router for VLAN 20

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we'll then test that failover actually takes place

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by doing a continuous ping between our PC's.

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Here’s the console of switch 1 at the moment

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sh ip int brief

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shows us the IP addresses configured

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on the relevant Switch Virtual Interfaces or SVIs on the switch.

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We'll start with VLAN 10

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so that’s the IP address configured on switch 1

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I'm going to type conf t

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to go to global config mode

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and then I’ll go to interface VLAN 10

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pressing question mark we can see the option standby

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which allows us to configure HSRP, so standby ?

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You can create multiple groups that allow you to split

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the sharing of who is the active router within a VLAN

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I’m not going to do that here, I'll simply creates a group of 1.

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Now you may want to make the group number the same as the VLAN number.

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In this case, I’m not going to do that because I simply want to show you

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that the same group number can be used on multiple VLANs

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so standby 1 specify an IP address

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and in this case, it’s the IP address of our virtual router

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which is going to be 10.1.10.254 for VLAN 10

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this HSRP router once again doesn’t exist

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we're simply configuring the virtual router.

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In this case, I’m going to configure a priority rather a standby priority

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of 200 the default is 100 but I want to influence the priority

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to ensure that switch 1 becomes the active router for VLAN 10.

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we can see already that this switch become the active router for VLAN 10 group 1

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if I do a show command, standby 1 preemption

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what preemption does is ensure that switch 1

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becomes the active router when it’s up, so switch 1 went down

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and switch 2 then became the active router, while switch 1 is down

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when switch 1 comes back again preemption will ensure that switch 1

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becomes the active router again

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so it will basically force itself to become the active device.

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we can view HSRP information by using the command show standby

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as you can see here VLAN 10 has group 1 configured

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the local router is the active router

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the virtual IP address is configured as follows.

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The active virtual MAC address is this

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so this is an HSRP MAC address

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this virtual router on VLAN 10 is using this MAC address.

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This portion of the MAC address is the HSRP well known MAC address

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so that is a reserved address for HSRP and this portion of the MAC address

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is a hexadecimal representation of the group number.

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Now we created group 1, so in hexadecimal, it's shown us 01

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if we had created a group of group 10 it would show us 0A

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A being hexadecimal for 10.

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Hello's are sent every 3 seconds, the hold-time is 10 seconds.

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at the moment, no hello's are being received from switch 2

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so switch 1 has become the active forwarder

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if there are multiple routers in the topology

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they will send keep-alive to each other

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and that is how they know whether the other device is available

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as an example, when switch 2 is configured

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it should be receiving hello's from switch 1 every 3 seconds

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if it doesn’t for a period of 10 seconds, it will become the active router.

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So it will move from standby to active and we'll test that in a moment.

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preemption is enabled the active router is the local router,

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the standby router currently is unknown

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we haven’t configured switch 2 with HSRP

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so switch 1 doesn’t know about any standby router

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at the moment, the local priority of the router is 200

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and this is the group name which is the default group name.

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So let’s configure switch 2 and see what happens in the election

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we'll configure switch 2 for VLAN 10

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and then we'll configure both routers with HSRP on VLAN 20.