The Problem occured while studying for my exams

Problem: I have to design a Network for a Company. The given IP Adress Space is which has to be divided into 4 Subnets. These Subnets share a Backbone, consistig of 2 Core Switches which are connected to the Internet via 2 redundant Routers (HSRP)

My question now: How many IP Adresses are needed for the redundant Router configuration in each subnet?

Sorry if this question is stupid or badly phrased, im a newbee

2 Answers 2


Each router will have its own address. The HSRP/VRRP group will have one virtual address shared by those in the group. (one active, one or more standby's)

  • ... except for the purely inter-router subnets as @SteveDugan has pointed out. Routers among themselves don't use a FHRP but a routing protocol like OSPF.
    – Zac67
    Aug 24, 2022 at 14:48
  • One can complain about the "bad" network setup all they want. It is what it is: a pair of routers using HSRP to present a single IP default gateway. That's going to take one address per router, and one per group.
    – Ricky
    Aug 25, 2022 at 22:34

The real problem here is that the author of the question you are trying to solve doesn't understand HSRP correctly! HSRP, as well as other FHRPs (VRRP, GLBP) are solutions to solve hsot to default gateway issues. A host can only be assigned a single default gateway, therefor if there is redundancy, a FHRP must be used. In the question you are being asked, they are using HSRP to comunicate from core switches to some redundant routers via HSRP. THIS IS WRONG! You should be routing (OSPF/EIGRP) from the core switches to the redundant internet routers.

To answer the other half of your question. When PROPERLY using HSRP/VRRP it will consume 3 addresses minimum. One for each router assigned to the interface, and one virtual address.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.