route Maps with OSPF for set ip next-hop

Discussion in 'Cisco' started by philbo30, Jul 16, 2007.

  1. philbo30

    philbo30 Guest

    Situation:

    3845 router with multiple Virtual Tunnel Interfaces facing the
    Internet and two Interfaces facing a PIX firewall.

    Need:
    Routes to certain tunnels must be available from the PIX via a
    specific interface (one of the two).

    Question:
    Can a route map be used with the outbound LSAs to specify the next hop
    that the PIX knows about ? In other words, I want to run a route map
    on the 3845 that sets the "ip next-hop" that is advertised into OSPF.

    For example, the PIX would then know that network 10.0.0.0 /24 is
    available via interface G0 on the 3845 router and network 11.0.0.0/24
    is available via interface G1 on the 3845 router.

    Note that I can make this happen by running 2 OSPF processes on the
    PIX and the router, but I would prefer to do it with route maps. Both
    interfaces on the 3845 router can be in the same area or different
    areas, whichever is necessary to make this thing work.

    Bottom line, can route maps with the set ip next-hop command be used
    to control the information that an OSPF participant receives?
    philbo30, Jul 16, 2007
    #1
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  2. philbo30

    Merv Guest


    > Bottom line, can route maps with the set ip next-hop command be used
    > to control the information that an OSPF participant receives?



    If the question is can outbound LSA's be modified using route maps,
    AFAIK this is not possible.

    There is now the ability to perform OSPF ABR Type 3 LSA Filtering -
    see
    http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080087be9.html

    If you ran BGP between the 3845 and the PIX, then doing what you want
    to do is easily accomplished by setting next hop via a BGP outbound
    route map.
    Merv, Jul 16, 2007
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  3. philbo30

    Guest

    On 16 Jul, 18:51, Merv <> wrote:
    > > Bottom line, can route maps with the set ip next-hop command be used
    > > to control the information that an OSPF participant receives?

    >
    > If the question is can outbound LSA's be modified using route maps,
    > AFAIK this is not possible.
    >
    > There is now the ability to perform OSPF ABR Type 3 LSA Filtering -
    > seehttp://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_featu...
    >
    > If you ran BGP between the 3845 and the PIX, then doing what you want
    > to do is easily accomplished by setting next hop via a BGP outbound
    > route map.


    I would think that such LSA filtering as requested
    by the OP would violate the OSPF architecture.

    OSPF does not advertise routes or next hops
    between routers, it instead sends information
    about the network topology. Every router in an area
    has the same information about the topology from
    which the next hops are (routing table entries)
    are determined. It is an absolute
    requirement (in order to avoid loops and provide
    reachability) that every router in an area
    has the same topology database and so
    filtering would not be possible.

    Between areas and between routing processes
    then things are different.
    , Jul 16, 2007
    #3
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