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help understanding OSPF

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  • help understanding OSPF


    I'm in the middle of trying to audit our internal networks but OSPF (To which I have a little understanding of) is hampering my search

    for example if the below appears in the sh ip route table

    O E2 [110/20] via *.*.*.*, 6d13h, Vlan101

    How do i locate what switch this network is actually connected to ?


  • #2
    Re: help understanding OSPF

    First you have to understand what that route entry means.

    The E2 means that this route was redistributed into OSPF from another routing protocol (RIP, EIGRP, via static etc....).

    The subnet learned is

    The 110 is the Administrative Distance for OSPF

    The 20 is the cost (metric) of the route (20 is the default for E2 routes. This is not the full path cost to the destination but the cost of the ASBR (Autonomous System Boundary Router) to the destination. If you want the full path cost it needs to be converted to an E1.

    The via is the next hop to reach the destination subnet.

    The VLAN101 is the local interface where the route was learned

    To find where that remote network originates just go to the next hop and work from there.
    CCNA, CCNA-Security, CCNP
    CCIE Security (In Progress)


    • #3
      Re: help understanding OSPF

      Thank you so very much