Any other way to..

Discussion in 'Cisco' started by robertandconchi@aol.com, Oct 16, 2008.

  1. Guest

    Is there any other recommended way besides creating stubs to filter
    out lsa type 5 routes ( static route redistribution) from a backbone
    area to another?

    thanks in advance.
     
    , Oct 16, 2008
    #1
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  2. John Agosta Guest

    <> wrote in message
    news:...
    > Is there any other recommended way besides creating stubs to filter
    > out lsa type 5 routes ( static route redistribution) from a backbone
    > area to another?
    >
    > thanks in advance.



    I would think an inbound route-map on the ABR that denies metric-types 1 and
    2 would do the trick.........

    -ja
     
    John Agosta, Oct 16, 2008
    #2
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  3. Stephen Guest

    On Thu, 16 Oct 2008 10:25:25 -0500, "John Agosta"
    <> wrote:

    >
    ><> wrote in message
    >news:...
    >> Is there any other recommended way besides creating stubs to filter
    >> out lsa type 5 routes ( static route redistribution) from a backbone
    >> area to another?
    >>
    >> thanks in advance.

    >
    >
    >I would think an inbound route-map on the ABR that denies metric-types 1 and
    >2 would do the trick.........


    AFAIR external routes are not filtered within OSPF - ie you cannot
    stop them propagating via the OSPF database between routers.
    So filtering at the ABR would alter the routing table on the ABR, but
    not stop those type 5 external routes propagating between areas.

    often the easiest way is to make sure they are not type 5 in the 1st
    place -
    Try using "passive interface" so a local route is OSPF rather than
    static, but prevent the source router forming an adjacency on the
    subnet.
    Or aggregate a bunch of statics at the point they get injected into
    OSPF using route maps.

    Have a look at NSSA areas - but cannot remember if they give you much
    control of externals.
    >
    >-ja
    >

    --
    Regards

    - replace xyz with ntl
     
    Stephen, Oct 16, 2008
    #3
  4. Guest

    On Oct 16, 5:09 pm, Stephen <> wrote:
    > On Thu, 16 Oct 2008 10:25:25 -0500, "John Agosta"
    >
    > <> wrote:
    >
    > ><> wrote in message
    > >news:....
    > >> Is there any other recommended way besides creating stubs to filter
    > >> out lsa type 5 routes ( static route redistribution) from a backbone
    > >> area to another?

    >
    > >> thanks in advance.

    >
    > >I would think an inbound route-map on the ABR that denies metric-types 1 and
    > >2 would do the trick.........

    >
    > AFAIR external routes are not filtered within OSPF - ie you cannot
    > stop them propagating via the OSPF database between routers.
    > So filtering at the ABR would alter the routing table on the ABR, but
    > not stop those type 5 external routes propagating between areas.
    >
    > often the easiest way is to make sure they are not type 5 in the 1st
    > place -
    > Try using "passive interface" so a local route is OSPF rather than
    > static, but prevent the source router forming an adjacency on the
    > subnet.
    > Or aggregate a bunch of statics at the point they get injected into
    > OSPF using route maps.
    >
    > Have a look at NSSA areas - but cannot remember if they give you much
    > control of externals.
    >
    > >-ja

    >
    > --
    > Regards
    >
    > - replace xyz with ntl


    could you elaborate a little more on your suggestion? I have a main
    router in area 0 with static routes and I want to prevent them from
    traversing through the ABR. I need adj between all routers.
     
    , Oct 17, 2008
    #4
  5. Merv Guest

    use BGP to carry the static if there are a lot of them - if not them
    do not worry about it
     
    Merv, Oct 17, 2008
    #5
  6. Guest

    On Oct 17, 4:03 am, Merv <> wrote:
    > use BGP to carry the static if there are a lot of them - if not them
    > do not worry about it


    thanks Merv. Still curious about this though.

    Try using "passive interface" so a local route is OSPF rather than
    static, but prevent the source router forming an adjacency on the
    subnet.

    a snippet would be great.
     
    , Oct 17, 2008
    #6
  7. John Agosta Guest

    <> wrote in message
    news:...
    On Oct 16, 5:09 pm, Stephen <> wrote:
    > On Thu, 16 Oct 2008 10:25:25 -0500, "John Agosta"
    >
    > <> wrote:
    >
    > ><> wrote in message
    > >news:...
    > >> Is there any other recommended way besides creating stubs to filter
    > >> out lsa type 5 routes ( static route redistribution) from a backbone
    > >> area to another?

    >
    > >> thanks in advance.

    >
    > >I would think an inbound route-map on the ABR that denies metric-types 1
    > >and
    > >2 would do the trick.........

    >
    > AFAIR external routes are not filtered within OSPF - ie you cannot
    > stop them propagating via the OSPF database between routers.
    > So filtering at the ABR would alter the routing table on the ABR, but
    > not stop those type 5 external routes propagating between areas.
    >
    > often the easiest way is to make sure they are not type 5 in the 1st
    > place -
    > Try using "passive interface" so a local route is OSPF rather than
    > static, but prevent the source router forming an adjacency on the
    > subnet.
    > Or aggregate a bunch of statics at the point they get injected into
    > OSPF using route maps.
    >
    > Have a look at NSSA areas - but cannot remember if they give you much
    > control of externals.
    >
    > >-ja

    >
    > --
    > Regards
    >
    > - replace xyz with ntl


    could you elaborate a little more on your suggestion? I have a main
    router in area 0 with static routes and I want to prevent them from
    traversing through the ABR. I need adj between all routers.


    Perhaps running two OSPF processes on the ABR and controlling via
    redistribution
    which routes are passed between area 0 and the non-0 area will work for you.
    Be careful not to send routes received from area 0 and passed into the non-0
    area,
    back towards area 0.....

    -ja
     
    John Agosta, Oct 17, 2008
    #7
  8. Stephen Guest

    On Thu, 16 Oct 2008 20:08:45 -0700 (PDT),
    wrote:

    >On Oct 16, 5:09 pm, Stephen <> wrote:
    >> On Thu, 16 Oct 2008 10:25:25 -0500, "John Agosta"
    >>
    >> <> wrote:
    >>
    >> ><> wrote in message
    >> >news:...
    >> >> Is there any other recommended way besides creating stubs to filter
    >> >> out lsa type 5 routes ( static route redistribution) from a backbone
    >> >> area to another?

    >>
    >> >> thanks in advance.

    >>
    >> >I would think an inbound route-map on the ABR that denies metric-types 1 and
    >> >2 would do the trick.........

    >>
    >> AFAIR external routes are not filtered within OSPF - ie you cannot
    >> stop them propagating via the OSPF database between routers.
    >> So filtering at the ABR would alter the routing table on the ABR, but
    >> not stop those type 5 external routes propagating between areas.
    >>
    >> often the easiest way is to make sure they are not type 5 in the 1st
    >> place -
    >> Try using "passive interface" so a local route is OSPF rather than
    >> static, but prevent the source router forming an adjacency on the
    >> subnet.
    >> Or aggregate a bunch of statics at the point they get injected into
    >> OSPF using route maps.
    >>
    >> Have a look at NSSA areas - but cannot remember if they give you much
    >> control of externals.
    >>
    >> >-ja

    >>
    >> --
    >> Regards
    >>
    >> - replace xyz with ntl

    >
    >could you elaborate a little more on your suggestion? I have a main
    >router in area 0 with static routes and I want to prevent them from
    >traversing through the ABR. I need adj between all routers.


    passive will only work for external routes from "connected" interface
    srouces.

    you have 2 places to filter an external route from a static in OSPF
    directly - where it enters the OSPF domain, and when it drops out of
    OSPF into a routing table.

    So you can stop your statics going into OSPF entrirely, or stop them
    getting into the routing table on other routers - but since OSPF
    replicates externals via the database, you would have to do that at
    each router.

    the other way is that exernals do not cross into a stub (totally
    stubby area in cisco speak) or NSSA area.

    So all externals within OSPF get aggregated into 1 default route if
    you set the area up as totally stubby or NSSA.

    However - why filter like this? i have a customer network with 3k
    internal routes, where many are externals (and since almost all is
    dual routers in parallel, there are 2 copies of each external in the
    database).

    Not much overhead for route propagation, processing or bandwidth.
    --
    Regards

    - replace xyz with ntl
     
    Stephen, Oct 17, 2008
    #8
  9. Stephen Guest

    On Fri, 17 Oct 2008 19:24:33 GMT, Stephen <>
    wrote:

    >On Thu, 16 Oct 2008 20:08:45 -0700 (PDT),
    >wrote:
    >
    >>On Oct 16, 5:09 pm, Stephen <> wrote:
    >>> On Thu, 16 Oct 2008 10:25:25 -0500, "John Agosta"
    >>>
    >>> <> wrote:
    >>>
    >>> ><> wrote in message
    >>> >news:...
    >>> >> Is there any other recommended way besides creating stubs to filter
    >>> >> out lsa type 5 routes ( static route redistribution) from a backbone
    >>> >> area to another?
    >>>
    >>> >> thanks in advance.
    >>>
    >>> >I would think an inbound route-map on the ABR that denies metric-types 1 and
    >>> >2 would do the trick.........
    >>>
    >>> AFAIR external routes are not filtered within OSPF - ie you cannot
    >>> stop them propagating via the OSPF database between routers.
    >>> So filtering at the ABR would alter the routing table on the ABR, but
    >>> not stop those type 5 external routes propagating between areas.
    >>>
    >>> often the easiest way is to make sure they are not type 5 in the 1st
    >>> place -
    >>> Try using "passive interface" so a local route is OSPF rather than
    >>> static, but prevent the source router forming an adjacency on the
    >>> subnet.
    >>> Or aggregate a bunch of statics at the point they get injected into
    >>> OSPF using route maps.
    >>>
    >>> Have a look at NSSA areas - but cannot remember if they give you much
    >>> control of externals.
    >>>
    >>> >-ja
    >>>
    >>> --
    >>> Regards
    >>>
    >>> - replace xyz with ntl

    >>
    >>could you elaborate a little more on your suggestion? I have a main
    >>router in area 0 with static routes and I want to prevent them from
    >>traversing through the ABR. I need adj between all routers.

    >
    >passive will only work for external routes from "connected" interface
    >srouces.
    >
    >you have 2 places to filter an external route from a static in OSPF
    >directly - where it enters the OSPF domain, and when it drops out of
    >OSPF into a routing table.
    >
    >So you can stop your statics going into OSPF entrirely, or stop them
    >getting into the routing table on other routers - but since OSPF
    >replicates externals via the database, you would have to do that at
    >each router.
    >
    >the other way is that exernals do not cross into a stub (totally
    >stubby area in cisco speak) or NSSA area.
    >
    >So all externals within OSPF get aggregated into 1 default route if
    >you set the area up as totally stubby or NSSA.
    >
    >However - why filter like this? i have a customer network with 3k
    >internal routes, where many are externals (and since almost all is
    >dual routers in parallel, there are 2 copies of each external in the
    >database).
    >
    >Not much overhead for route propagation, processing or bandwidth.


    OSPF design guide on the cisco site may be useful:
    http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml
    --
    Regards

    - replace xyz with ntl
     
    Stephen, Oct 17, 2008
    #9
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