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HSRP Senarios

Hallo again,

i know that hsrp with layer3 can work in one of 3 senarios either vlan isl , bridging or pim protocol , is there another possibility to let it work with ospf , i know that multicast ospf over cisco switches is not supported. is it supported on other vnedors (nortel, foundry, extreme ,,,,,,,)or not?

many thanks in advance.

Hallo All,

i need to know if i like to build a hsrp net as the following

we have 2 seperate networks

the first is a DIS router (above this router there is a core router ) connected to two routers the running routing protocol is OSPF

we like to connect this 2 access routers (a , b)to the costumer network wihch is the second network.

here is the story

i like to know how many hsrp solution can we implement

1- first senario : costumer network it is two core switches working on layer 3 (i mean routing protocol running only either ospf or rip) and one switch has one connection for router access a, and the other switch has one connection for router access b

do you think this senarion could work , do we required to connect the 2 layer 3 switches over layer 3 link or must through layer 2 link or if whatever will no work.

2- the second senario will it work if the costumer network has one core switch working on layer 3.

3,4- i think that costumer network has layer 2 (1 switch, 2 switches) will work fine with one switch has one link to acc router a and other switch has one link to acc router b.

i would like to thank you all for reading this long massege.

Best regards,


P.S. i will give one senario visio drawing of them as reference.

  • LAN Switching and Routing

Re: HSRP Senarios

A set of routers that run HSRP works in concert to present the illusion of a single default gateway router to the hosts on the LAN. This set of routers is known as an HSRP group or standby group. A single router that is elected from the group is responsible for the forwarding of the packets that hosts send to the virtual router. This router is known as the active router. Another router is elected as the standby router. If the active router fails, the standby assumes the packet forwarding duties. Although an arbitrary number of routers may run HSRP, only the active router forwards the packets that are sent to the virtual router IP address.

In order to minimize network traffic, only the active and the standby routers send periodic HSRP messages after the protocol has completed the election process. Additional routers in the HSRP group remain in the initial state. If the active router fails, the standby router takes over as the active router. If the standby router fails or becomes the active router, another router is elected as the standby router.

Each standby group emulates a single virtual router (default gateway). For each group, a single well-known MAC and IP address is allocated to that group. Multiple standby groups can coexist and overlap on a LAN, and individual routers can participate in multiple groups. In this case, the router maintains a separate state and timers for each group.


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