6500 MSFC and HSRP subnet masks

Discussion in 'Cisco' started by GJP, Dec 9, 2004.

  1. GJP

    GJP Guest

    I am currently configuring the routing interfaces on 6500 MSFCs.

    When a standby IP is added to an interface how does the router know
    how you are subnetting the IP ranges?

    For instance if I enter as a standby IP how does it know
    whether I am using an 8, 16, 24 or even a 27 bit subnet mask?

    It does not enforce entering a subnet mask when you add a standby IP.
    GJP, Dec 9, 2004
    1. Advertisements

  2. Well,
    the router is quite intelligent, isn't it? It does so by magic :)

    The router does have all information required to do so. It has
    1. The IP-address AND Subnetmask for the interface
    2. the virtual (standby) ip-address
    If now, and the cli ensures that, the standby ip-address is in the range
    of the subnet defined by (1), the subnet is defined.

    Or, see it that way: A standby address is just another IP-address in the
    range of the subnet defined by ip-address/subnetmask of the physical
    interface. It does not need to know anything about subnetting at that stage.

    CCIE #11220
    Everything written is MY opinion only, not the one of my company or
    employer unless otherwise noted

    The early bird gets the worm, but the second mouse gets the cheese

    My signature is certified by Fraunhofer Society.
    The root-ca IS trusted but the browser-manufacturers want big $ to have
    it included
    Mathias Gaertner, Dec 9, 2004
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.