Which of the following statements is true about the Hot Standby Router Protocol (HSRP) in a network?
A) HSRP allows multiple routers to share the same IP address to provide load balancing across routers.
B) HSRP provides redundancy by allowing a primary and standby router to share a virtual IP address, where the standby router takes over if the primary router fails.
C) HSRP is used to dynamically assign IP addresses to devices on a network.
D) HSRP is a routing protocol that selects the best path based on hop count.
Correct Answer:
B) HSRP provides redundancy by allowing a primary and standby router to share a virtual IP address, where the standby router takes over if the primary router fails.
Detailed Explanations:
A) HSRP allows multiple routers to share the same IP address to provide load balancing across routers.
This statement is incorrect. While HSRP does allow multiple routers to share a virtual IP address, its primary function is not to provide load balancing, but rather redundancy. HSRP is designed to ensure high availability by enabling a backup router to take over if the primary router fails. In an HSRP group, one router is designated as the “active” router and another as the “standby” router. The active router is responsible for forwarding packets sent to the virtual IP address, while the standby router monitors the active router’s status. If the active router fails, the standby router takes over the virtual IP address, ensuring continuous network availability.
Load balancing, on the other hand, is a function that distributes network traffic across multiple routers to optimize resource use, decrease response times, and avoid overloading any single router. While there are protocols like GLBP (Gateway Load Balancing Protocol) that can achieve load balancing, HSRP is not designed for this purpose. HSRP focuses solely on redundancy and failover rather than traffic distribution.
B) HSRP provides redundancy by allowing a primary and standby router to share a virtual IP address, where the standby router takes over if the primary router fails.
This statement is correct. HSRP (Hot Standby Router Protocol) is a Cisco proprietary protocol that provides redundancy for IP networks. The primary goal of HSRP is to ensure that the failure of a single router does not cause a network outage. It achieves this by allowing a group of routers to share a virtual IP address, which is the address that hosts on the local network use as their gateway.
In an HSRP group, one router is elected as the “active” router, responsible for forwarding packets sent to the virtual IP address. A second router is elected as the “standby” router. If the active router fails (due to a hardware issue, network failure, etc.), the standby router automatically takes over as the active router, assuming the virtual IP address and continuing to forward traffic without interruption. This process is seamless to end-users, who experience little to no disruption in network connectivity.
HSRP uses a priority value to determine which router becomes the active router in the group. The router with the highest priority becomes the active router. If two routers have the same priority, the one with the higher IP address becomes the active router. Network administrators can also influence which router becomes active by configuring HSRP preemption, which allows a higher priority router to take over as the active router if it becomes available after a failure.
C) HSRP is used to dynamically assign IP addresses to devices on a network.
This statement is incorrect. HSRP does not have any functionality related to the dynamic assignment of IP addresses. The protocol responsible for dynamically assigning IP addresses to devices on a network is DHCP (Dynamic Host Configuration Protocol). DHCP automates the process of assigning IP addresses, subnet masks, default gateways, and other network settings to devices on a network, ensuring that each device has a unique IP address and appropriate configuration.
HSRP, in contrast, is concerned with providing redundancy and ensuring that there is always an active gateway available for network devices to use. It operates at a different layer of the network stack and is focused on maintaining availability rather than managing IP address assignments.
D) HSRP is a routing protocol that selects the best path based on hop count.
This statement is incorrect. HSRP is not a routing protocol, nor does it select paths based on hop count or any other metric. Routing protocols like RIP (Routing Information Protocol) and OSPF (Open Shortest Path First) are responsible for determining the best path through a network by analyzing various metrics, such as hop count, bandwidth, delay, or other factors, depending on the specific protocol.
HSRP, on the other hand, is not concerned with path selection. Instead, it operates in the context of a single network segment to ensure that there is a redundant gateway available at all times. The routers within an HSRP group cooperate to present a single virtual router to the network, and this virtual router is used as the default gateway by devices on that network segment. The actual routing decisions—such as which path to take to reach a particular destination—are made by the active router using its routing table, which is populated by a separate routing protocol.