OSPF Question

Discussion in 'Cisco' started by timo, Dec 29, 2003.

  1. timo

    timo Guest

    Hey

    Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
    VLANs are setup on both MSFCs except for a few specifics.

    To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
    1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
    This is an administrative hassle bc whenever a new VLAN is created we have
    to remember to do ip ospf cost 2 or load sharing occurs . This extra step
    is tedious, plus I really dont need OSPF running on most of these interfaces
    anyway (I think ) because 1. there are no other OSPF routers on these VLANs
    and 2. since both MSFCs have connected interfaces they can route traffic
    from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
    all VLAN interfaces that are on both MSFCs.

    If I were to remove all the ip ospf cost cmd's, add passive interface
    default and no passive interface vlan3 to both router ospf configs would
    there be any downsides ? I see lots of benefits like - dont have to worry
    about rogue routers on end user vlan poisioning route tables , - less CPU
    util since no SPF algo running for all these passive interfaces, -less admin
    work (no more need for ip ospf cost 2) ... I cant think of any downsides...

    Take a look at this example
    http://box1.theglens.net/net/ip-ospf-issue.gif


    Thanks

    Timo
    timo, Dec 29, 2003
    #1
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  2. timo

    Mike Guest

    timo wrote:

    > Hey
    >
    > Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
    > VLANs are setup on both MSFCs except for a few specifics.
    >
    > To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
    > 1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
    > This is an administrative hassle bc whenever a new VLAN is created we have
    > to remember to do ip ospf cost 2 or load sharing occurs . This extra step
    > is tedious, plus I really dont need OSPF running on most of these interfaces
    > anyway (I think ) because 1. there are no other OSPF routers on these VLANs
    > and 2. since both MSFCs have connected interfaces they can route traffic
    > from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
    > all VLAN interfaces that are on both MSFCs.
    >
    > If I were to remove all the ip ospf cost cmd's, add passive interface
    > default and no passive interface vlan3 to both router ospf configs would
    > there be any downsides ? I see lots of benefits like - dont have to worry
    > about rogue routers on end user vlan poisioning route tables , - less CPU
    > util since no SPF algo running for all these passive interfaces, -less admin
    > work (no more need for ip ospf cost 2) ... I cant think of any downsides...
    >
    > Take a look at this example
    > http://box1.theglens.net/net/ip-ospf-issue.gif
    >
    >
    > Thanks
    >
    > Timo

    That is exactly what I would do. Works great.
    Mike, Dec 29, 2003
    #2
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  3. timo

    Hansang Bae Guest

    In article <>,
    says...
    > Hey
    >
    > Ive got 2 6509 \w MSFC2 connected to each other with about 15 VLANs. Most
    > VLANs are setup on both MSFCs except for a few specifics.
    >
    > To keep traffic between the 2 switches on a specific VLAN I use ip ospf cost
    > 1 on the interswitch VLAN3 and 'ip ospf cost 2' on all other VLANs 1,2.
    > This is an administrative hassle bc whenever a new VLAN is created we have
    > to remember to do ip ospf cost 2 or load sharing occurs . This extra step
    > is tedious, plus I really dont need OSPF running on most of these interfaces
    > anyway (I think ) because 1. there are no other OSPF routers on these VLANs
    > and 2. since both MSFCs have connected interfaces they can route traffic
    > from the interswitch VLAN to the destination VLAN. I have HSRP config'd on
    > all VLAN interfaces that are on both MSFCs.
    >
    > If I were to remove all the ip ospf cost cmd's, add passive interface
    > default and no passive interface vlan3 to both router ospf configs would
    > there be any downsides ? I see lots of benefits like - dont have to worry
    > about rogue routers on end user vlan poisioning route tables , - less CPU
    > util since no SPF algo running for all these passive interfaces, -less admin
    > work (no more need for ip ospf cost 2) ... I cant think of any downsides...
    >
    > Take a look at this example
    > http://box1.theglens.net/net/ip-ospf-issue.gif


    Not really. But you don't have any redundant connections between the
    two. Even that won't matter in some cases (though it's not a good
    design practice).

    --

    hsb

    "Somehow I imagined this experience would be more rewarding" Calvin
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    Hansang Bae, Dec 30, 2003
    #3
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