HSRP (Hot Standby Router Protocol)

HSRP (Hot Standby Router Protocol)

Purpose:

• HSRP is a Cisco proprietary redundancy protocol used to provide high availability for IP networks, primarily in router environments.
• It allows for the automatic failover of a router in the event of a failure, ensuring minimal disruption to network traffic.

HSRP State

• Initial statge -- when interface just got enable for congratulations HSRP.
• Listening mod ---Router knows the virtual ip address and will listen for hello message from other HSRP router
• Speak mode --- the router will send the hello message and will join the election to see which router will become a active or standby
• Standby ---the router didn't become the active router but will keep sending hello message. If the active router fail it will take over.
• Active ----the router will actively forward packets from client and sends hello message.
• Hello timer 3 sec
• hold timer 10 sec
• every router of priority by default 100
• HSRP router of max priority by 255
• Hello send multicast IP add 224.0.0.2
• Version 1, version 2 multicast address 224.0.0.102

2. Components:

• Active Router: The router that currently forwards packets sent to the virtual IP address.
• Standby Router(s): The router(s) that are ready to take over forwarding if the active router fails.
• Virtual IP Address: An IP address shared between the routers in the HSRP group, representing the default gateway for hosts on the network.

3. Group Configuration:

• Routers participating in HSRP belong to the same HSRP group, identified by a numeric group ID (0-255).
• Each group has a unique virtual IP address.

4. Router Priority:

• Each router in the HSRP group has a priority value (1-255), indicating its suitability to become the active router.
• The router with the highest priority becomes the active router.
• If priorities are tied, the router with the highest IP address on the HSRP interface becomes the active router.

5. Preemption:

• Preemption allows a higher priority router to preempt a lower priority router and become the active router.
• By default, preemption is disabled, but it can be enabled using the standby <group-number> preempt command.

6. Tracking:

• HSRP allows routers to track the status of certain interfaces or routes.
• If a tracked interface or route goes down, the router's HSRP priority is decremented, making it less likely to become the active router.
• Tracking helps ensure that the active router is only active if it has access to necessary resources.

7. Versions:

• HSRP has multiple versions, including HSRPv1 and HSRPv2.
• HSRPv2 introduces support for IPv6 and provides additional features compared to HSRPv1.

8. Security:

• HSRP messages are sent using IP protocol 112 (UDP).
• HSRPv2 supports authentication using MD5 authentication keys to prevent unauthorized routers from participating in the HSRP group.

9. Configuration and Verification:

• HSRP configuration is done at the interface level.
• Commonly used commands for configuring and verifying HSRP include standby, show standby, and debug standby.

10. Use Cases:

• HSRP is commonly used in enterprise networks, data centers, and any environment where high availability and fault tolerance are critical.
• It ensures uninterrupted connectivity for end devices by providing redundant routing paths.
• HSRP is a fundamental protocol for ensuring network reliability and is widely deployed in Cisco-based networks. Understanding its features and configuration options is essential for network engineers responsible for designing and managing resilient network architectures.

Configuration HSRP

Step 1: Configure IP Addresses on Interfaces:

Step 2: Enable HSRP on Interfaces:

Step 3: Verify Configuration:

Troubleshooting HSRP:

Step 1: Check HSRP State:

    
Step 2: Verify Interface Status:

Step 3: Check HSRP Configuration:

Step 4: Debug HSRP Events (Optional - Caution: Can Generate a Lot of Output):

Step 5: Check Tracking Status:

Step 6: Verify HSRP Neighborship:

Step 7: Review HSRP Statistics:

• Ensure to replace interface numbers, IP addresses, priorities, and tracking interfaces with your actual configurations. Additionally, be cautious when using debugging commands in a production environment, as they can generate a lot of output and impact router performance. These steps should help you configure and troubleshoot HSRP effectively on your Cisco routers.