route-map

Discussion in 'Cisco' started by mmark751969, Mar 24, 2008.

  1. mmark751969

    mmark751969 Guest

    i am looking at a 7206 router configuration with the following
    statement 'route-map ISP-IN permit 10'. There is no information that
    follows this for this route map(no match or set statements). What
    purpose can this serve. Thanks
     
    mmark751969, Mar 24, 2008
    #1
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  2. mmark751969

    Trendkill Guest

    On Mar 24, 3:21 pm, mmark751969 <> wrote:
    > i am looking at a 7206 router configuration with the following
    > statement 'route-map ISP-IN permit 10'. There is no information that
    > follows this for this route map(no match or set statements). What
    > purpose can this serve. Thanks


    I doubt anything. If there is no match statement that references an
    access-list, then even if a routing protocol was using the route-map,
    there are no addresses to match on and therefore prioritize. I would
    presume it was a legacy statement for BGP preference setting w/ your
    ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    one ISP over the other or something, along with prepends? Just
    guessing, but I don't think it can do anything without a match
    statement. Else someone else on here will surely speak up.
     
    Trendkill, Mar 24, 2008
    #2
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  3. mmark751969

    p_teatreeoil Guest

    On Mar 24, 2:21 pm, mmark751969 <> wrote:
    > i am looking at a 7206 router configuration with the following
    > statement 'route-map ISP-IN permit 10'. There is no information that
    > follows this for this route map(no match or set statements). What
    > purpose can this serve. Thanks


    It isn't doing anything that I know of. Do a:

    show run | i route-map ISP-IN

    If the only match you get is the route-map itself, then it isn't
    applied to anything and you might as well delete it.

    It could be some kind of hack or workaround for a crappy IOS, but I'm
    not familiar with it.
     
    p_teatreeoil, Mar 25, 2008
    #3
  4. mmark751969

    Trendkill Guest

    On Mar 27, 10:36 am, wrote:
    > In article <>, Trendkill <> writes:
    >
    > > On Mar 24, 3:21 pm, mmark751969 <> wrote:
    > >> i am looking at a 7206 router configuration with the following
    > >> statement 'route-map ISP-IN permit 10'. There is no information that
    > >> follows this for this route map(no match or set statements). What
    > >> purpose can this serve. Thanks

    >
    > > I doubt anything. If there is no match statement that references an
    > > access-list, then even if a routing protocol was using the route-map,
    > > there are no addresses to match on and therefore prioritize.

    >
    > In the absence of any match clauses, the route-map entry matches
    > everything, yes? Documentation says that "all" match clauses must match.
    > If there are no match clauses, that condition is vacuously satisfied.
    > That means that this route-map matches all traffic.
    >
    > However, if the route-map were removed, I assume that the resulting
    > configuration would match no traffic.
    >
    > > I would
    > > presume it was a legacy statement for BGP preference setting w/ your
    > > ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    > > one ISP over the other or something, along with prepends? Just
    > > guessing, but I don't think it can do anything without a match
    > > statement. Else someone else on here will surely speak up.

    >
    > Or it could simply be a filter on which ISP routes to accept.
    >
    > e.g.
    >
    > route-map ISP-IN permit 10
    >
    > router bgp 12345
    > ...
    > neighbor isp.address.goes.here route-map ISP-IN in
    > ...
    >
    > As things stand, he gets all ISP routes.
    > Delete the route-map and he gets no ISP routes.
    > Delete the neighbor clause and he gets all ISP routes.
    >
    > If he _wants_ to filter ISP-learned routes then the right move is to
    > populate the route-map with match clauses using prefix-lists, access
    > lists, AS-paths or similar.
    >
    > If he just wants to clean up the config then he should remove the
    > neighbor clause and then remove the route map. And then he should
    > reset the ISP peering session and make sure that things still work as
    > expected. (clear ip bgp isp.address.goes.here soft in)


    Interesting, although he never confirmed that he did have it applied
    on any neighbor statement. I'm still not sure why you would have a
    map to adjust basically nothing on everything (all routes). Still
    seems like a legacy statement left in or something not fully
    implemented that nobody every fixed or questioned.
     
    Trendkill, Mar 27, 2008
    #4
  5. mmark751969

    Trendkill Guest

    On Mar 27, 11:22 am, wrote:
    > In article <>, Trendkill <> writes:
    >
    >
    >
    > > On Mar 27, 10:36 am, wrote:
    > >> In article <>, Trendkill <> writes:

    >
    > >> > On Mar 24, 3:21 pm, mmark751969 <> wrote:
    > >> >> i am looking at a 7206 router configuration with the following
    > >> >> statement 'route-map ISP-IN permit 10'. There is no information that
    > >> >> follows this for this route map(no match or set statements). What
    > >> >> purpose can this serve. Thanks

    >
    > >> > I doubt anything. If there is no match statement that references an
    > >> > access-list, then even if a routing protocol was using the route-map,
    > >> > there are no addresses to match on and therefore prioritize.

    >
    > >> In the absence of any match clauses, the route-map entry matches
    > >> everything, yes? Documentation says that "all" match clauses must match.
    > >> If there are no match clauses, that condition is vacuously satisfied.
    > >> That means that this route-map matches all traffic.

    >
    > >> However, if the route-map were removed, I assume that the resulting
    > >> configuration would match no traffic.

    >
    > >> > I would
    > >> > presume it was a legacy statement for BGP preference setting w/ your
    > >> > ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    > >> > one ISP over the other or something, along with prepends? Just
    > >> > guessing, but I don't think it can do anything without a match
    > >> > statement. Else someone else on here will surely speak up.

    >
    > >> Or it could simply be a filter on which ISP routes to accept.

    >
    > >> e.g.

    >
    > >> route-map ISP-IN permit 10

    >
    > >> router bgp 12345
    > >> ...
    > >> neighbor isp.address.goes.here route-map ISP-IN in
    > >> ...

    >
    > >> As things stand, he gets all ISP routes.
    > >> Delete the route-map and he gets no ISP routes.
    > >> Delete the neighbor clause and he gets all ISP routes.

    >
    > >> If he _wants_ to filter ISP-learned routes then the right move is to
    > >> populate the route-map with match clauses using prefix-lists, access
    > >> lists, AS-paths or similar.

    >
    > >> If he just wants to clean up the config then he should remove the
    > >> neighbor clause and then remove the route map. And then he should
    > >> reset the ISP peering session and make sure that things still work as
    > >> expected. (clear ip bgp isp.address.goes.here soft in)

    >
    > > Interesting, although he never confirmed that he did have it applied
    > > on any neighbor statement. I'm still not sure why you would have a
    > > map to adjust basically nothing on everything (all routes). Still
    > > seems like a legacy statement left in or something not fully
    > > implemented that nobody every fixed or questioned.

    >
    > Agreed on both counts. He never indicated whether the route-map was
    > actually referred to elsewhere in the configuration. And the route-map
    > is most likely either either left-over cruft or not-fully-implemented
    > cruft.
    >
    > The key point that I'd hoped to make was that even though this route-map
    > doesn't _do_ much, deleting it could have nasty consequences if
    > it is still referred to and if one didn't clean up those dangling
    > references first.
    >
    > Clearly if it is not referred to then it is not doing anything and
    > can be safely removed.


    Yes, and I definitely appreciate you clearing that up for me. Out of
    experience, I would have ripped it off the neighbor statement first
    and then cleared the actual map (can't think of a single instance
    where this isn't the best thing to do except when just replacing an
    ACL or map), but definitely a good thing to keep in the back of my
    mind going forward. I don't think I would have expected that to be
    the way it is, as usually networking software is not assumption-based,
    as it seems in this case.
     
    Trendkill, Mar 27, 2008
    #5
  6. mmark751969

    Guest

    In article <>, Trendkill <> writes:
    > On Mar 24, 3:21 pm, mmark751969 <> wrote:
    >> i am looking at a 7206 router configuration with the following
    >> statement 'route-map ISP-IN permit 10'. There is no information that
    >> follows this for this route map(no match or set statements). What
    >> purpose can this serve. Thanks

    >
    > I doubt anything. If there is no match statement that references an
    > access-list, then even if a routing protocol was using the route-map,
    > there are no addresses to match on and therefore prioritize.


    In the absence of any match clauses, the route-map entry matches
    everything, yes? Documentation says that "all" match clauses must match.
    If there are no match clauses, that condition is vacuously satisfied.
    That means that this route-map matches all traffic.

    However, if the route-map were removed, I assume that the resulting
    configuration would match no traffic.

    > I would
    > presume it was a legacy statement for BGP preference setting w/ your
    > ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    > one ISP over the other or something, along with prepends? Just
    > guessing, but I don't think it can do anything without a match
    > statement. Else someone else on here will surely speak up.


    Or it could simply be a filter on which ISP routes to accept.

    e.g.

    route-map ISP-IN permit 10

    router bgp 12345
    ...
    neighbor isp.address.goes.here route-map ISP-IN in
    ...

    As things stand, he gets all ISP routes.
    Delete the route-map and he gets no ISP routes.
    Delete the neighbor clause and he gets all ISP routes.

    If he _wants_ to filter ISP-learned routes then the right move is to
    populate the route-map with match clauses using prefix-lists, access
    lists, AS-paths or similar.

    If he just wants to clean up the config then he should remove the
    neighbor clause and then remove the route map. And then he should
    reset the ISP peering session and make sure that things still work as
    expected. (clear ip bgp isp.address.goes.here soft in)
     
    , Mar 27, 2008
    #6
  7. mmark751969

    Guest

    In article <>, Trendkill <> writes:
    > On Mar 27, 10:36 am, wrote:
    >> In article <>, Trendkill <> writes:
    >>
    >> > On Mar 24, 3:21 pm, mmark751969 <> wrote:
    >> >> i am looking at a 7206 router configuration with the following
    >> >> statement 'route-map ISP-IN permit 10'. There is no information that
    >> >> follows this for this route map(no match or set statements). What
    >> >> purpose can this serve. Thanks

    >>
    >> > I doubt anything. If there is no match statement that references an
    >> > access-list, then even if a routing protocol was using the route-map,
    >> > there are no addresses to match on and therefore prioritize.

    >>
    >> In the absence of any match clauses, the route-map entry matches
    >> everything, yes? Documentation says that "all" match clauses must match.
    >> If there are no match clauses, that condition is vacuously satisfied.
    >> That means that this route-map matches all traffic.
    >>
    >> However, if the route-map were removed, I assume that the resulting
    >> configuration would match no traffic.
    >>
    >> > I would
    >> > presume it was a legacy statement for BGP preference setting w/ your
    >> > ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    >> > one ISP over the other or something, along with prepends? Just
    >> > guessing, but I don't think it can do anything without a match
    >> > statement. Else someone else on here will surely speak up.

    >>
    >> Or it could simply be a filter on which ISP routes to accept.
    >>
    >> e.g.
    >>
    >> route-map ISP-IN permit 10
    >>
    >> router bgp 12345
    >> ...
    >> neighbor isp.address.goes.here route-map ISP-IN in
    >> ...
    >>
    >> As things stand, he gets all ISP routes.
    >> Delete the route-map and he gets no ISP routes.
    >> Delete the neighbor clause and he gets all ISP routes.
    >>
    >> If he _wants_ to filter ISP-learned routes then the right move is to
    >> populate the route-map with match clauses using prefix-lists, access
    >> lists, AS-paths or similar.
    >>
    >> If he just wants to clean up the config then he should remove the
    >> neighbor clause and then remove the route map. And then he should
    >> reset the ISP peering session and make sure that things still work as
    >> expected. (clear ip bgp isp.address.goes.here soft in)

    >
    > Interesting, although he never confirmed that he did have it applied
    > on any neighbor statement. I'm still not sure why you would have a
    > map to adjust basically nothing on everything (all routes). Still
    > seems like a legacy statement left in or something not fully
    > implemented that nobody every fixed or questioned.


    Agreed on both counts. He never indicated whether the route-map was
    actually referred to elsewhere in the configuration. And the route-map
    is most likely either either left-over cruft or not-fully-implemented
    cruft.

    The key point that I'd hoped to make was that even though this route-map
    doesn't _do_ much, deleting it could have nasty consequences if
    it is still referred to and if one didn't clean up those dangling
    references first.

    Clearly if it is not referred to then it is not doing anything and
    can be safely removed.
     
    , Mar 27, 2008
    #7
  8. In article <EaXPp1I$>,
    wrote:

    > In article
    > <>,
    > Trendkill <> writes:
    > > On Mar 27, 10:36 am, wrote:
    > >> In article
    > >> <>,
    > >> Trendkill <> writes:
    > >>
    > >> > On Mar 24, 3:21 pm, mmark751969 <> wrote:
    > >> >> i am looking at a 7206 router configuration with the following
    > >> >> statement 'route-map ISP-IN permit 10'. There is no information that
    > >> >> follows this for this route map(no match or set statements). What
    > >> >> purpose can this serve. Thanks
    > >>
    > >> > I doubt anything. If there is no match statement that references an
    > >> > access-list, then even if a routing protocol was using the route-map,
    > >> > there are no addresses to match on and therefore prioritize.
    > >>
    > >> In the absence of any match clauses, the route-map entry matches
    > >> everything, yes? Documentation says that "all" match clauses must match.
    > >> If there are no match clauses, that condition is vacuously satisfied.
    > >> That means that this route-map matches all traffic.
    > >>
    > >> However, if the route-map were removed, I assume that the resulting
    > >> configuration would match no traffic.
    > >>
    > >> > I would
    > >> > presume it was a legacy statement for BGP preference setting w/ your
    > >> > ISP(s)? Probably had an access-list w/ networks/masks to prioritize
    > >> > one ISP over the other or something, along with prepends? Just
    > >> > guessing, but I don't think it can do anything without a match
    > >> > statement. Else someone else on here will surely speak up.
    > >>
    > >> Or it could simply be a filter on which ISP routes to accept.
    > >>
    > >> e.g.
    > >>
    > >> route-map ISP-IN permit 10
    > >>
    > >> router bgp 12345
    > >> ...
    > >> neighbor isp.address.goes.here route-map ISP-IN in
    > >> ...
    > >>
    > >> As things stand, he gets all ISP routes.
    > >> Delete the route-map and he gets no ISP routes.
    > >> Delete the neighbor clause and he gets all ISP routes.
    > >>
    > >> If he _wants_ to filter ISP-learned routes then the right move is to
    > >> populate the route-map with match clauses using prefix-lists, access
    > >> lists, AS-paths or similar.
    > >>
    > >> If he just wants to clean up the config then he should remove the
    > >> neighbor clause and then remove the route map. And then he should
    > >> reset the ISP peering session and make sure that things still work as
    > >> expected. (clear ip bgp isp.address.goes.here soft in)

    > >
    > > Interesting, although he never confirmed that he did have it applied
    > > on any neighbor statement. I'm still not sure why you would have a
    > > map to adjust basically nothing on everything (all routes). Still
    > > seems like a legacy statement left in or something not fully
    > > implemented that nobody every fixed or questioned.

    >
    > Agreed on both counts. He never indicated whether the route-map was
    > actually referred to elsewhere in the configuration. And the route-map
    > is most likely either either left-over cruft or not-fully-implemented
    > cruft.


    It might be a placeholder. In a large network, it's common to have
    configuration templates. So perhaps every machine is required to have
    this route-map, but the content varies by machine, and it can be empty
    if nothing needs to be put in it.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE don't copy me on replies, I'll read them in the group ***
     
    Barry Margolin, Mar 28, 2008
    #8
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