Free CCNA Labs: Packet Tracer Assessment: First Hop Redundancy Protocol (FHRP)
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In the previous exercise, the client devices in the Tyrell Corporation network had DHCP deployed. DHCP is much more favourable to employee mobility and provides a scalability solution for the large numbers of clients in the enterprise network. The initial layer 2 Local VLAN and Trunking configurations unique to each device have been applied and the STP features have been deployed including load-sharing, rapid spanning-tree and layer 2 protection features.
You are tasked with configuring First Hop Router Protocol (FHRP) features in this scenario. Implementing FHRP will provide a resilient gateway solution in the event of either one of the Distribution Switches having connectivity issues. When you have completed the tasks, you will be able to Check Results.
1. Enable IP routing on the Distribution Switches 1DSW1 and 1DSW2
2. Uplink interfaces to the Core Switches should be enabled. However, this should be implemented in such a way as to create a finite failure domain for Switch Block 1. All layer 2 potential failure scenarios must be contained within the Switch Block and not impact the Core Switches CSW1 and CSW2.
3. Implement the supported Cisco proprietary first hop router protocol on the Distribution switches to provide a redundant gateway solution for the client PCs in the access VLANS. The solution should achieve the following:
a. The single active gateway that responds to the ARP requests and forwards the traffic for each VLAN must follow the layer 2 STP topology.
b. The Layer 3 Active gateway should be configured to run alongside the preferred layer 2 STP Root Bridge for each access VLAN
c. The Layer 3 Standby gateway should be configured to run alongside the preferred Layer 2 STP Backup Root Bridge for each access VLAN
d. The IP address used for the Active and Standby routers should be configured to match the settings in the recently configured DHCP pools for each access VLAN.
e. The active forwarding gateway for each access VLAN should be configured with a priority 10 higher than the default FHRP priority. The standby gateway should not have their priorities altered.
f. In the event that any Standby gateway loses communication with the Active gateway due to an outage in the VLAN, the Standby gateway should move to the Active state as quickly as possible.
g. After any outage is restored within the VLAN, the higher priority gateway should regain the Active status and forwarding should be returned through the preferred gateway according to the design criteria.
h. The design also calls for each preferred Active gateway in the VLAN to monitor the Gigabit uplinks to the core switches. In the event of a failure of the first uplink the priority of the switch to be reduced by a default value. In the event of a further failure of the second uplink, the priority of the active gateway should fall to below that of the backup gateway. With both uplinks failed, the redundant gateway should immediately take control and begin forwarding in the group.
i. When only one of the uplinks to the Core Switches is restored, the Backup Gateway should retain forwarding the traffic for each affected VLAN. Not until both uplinks to the core are restored should the preferred gateway regain the Active status and forward the traffic for the VLANS.
Important Note: For the purpose of scoring the lab tasks, failover does not need to be tested. The scoring system will be based on the configuration of the preferred and backup gateways prior to any failover.
Packet Tracer behaves like older IOS versions in this scenario. The decrement in the gateway priority is not cumulative if you do not explicitly define the decrement value in the standby track command. The problem with Packet Tracer here is that it does not allow you to enter the decrement value, and so when the two uplinks fail the default decrement values are not added together to initiate the failover.
In modern IOS and vIOS, this is different and the decrement values are added together. The result would be the primary gateway priority is lowered to below that of the backup gateway, and the backup gateway begins the forwarding role.