Re: Conditional Advertise

For this u gotta use the CONTINUE Clause in route-maps

Filtering Traffic Using Continue Clauses in a BGP Route Map

Perform this task to filter traffic using continue clauses in a BGP route
map. In Cisco IOS Release 12.3(2)T, 12.0(24)S, 12.2(33)SRB, and later
releases, the continue clause was introduced into BGP route map
configuration. The continue clause allows for more programmable policy
configuration and route filtering and introduced the capability to execute
additional entries in a route map after an entry is executed with successful
match and set clauses. Continue clauses allow the network operator to
configure and organize more modular policy definitions so that specific
policy configurations need not be repeated within the same route map. Before
the continue clause was introduced, route map configuration was linear and
did not allow any control over the flow of a route map.

In Cisco IOS Release 12.0(31)S, 12.4(4)T, 12.2(33)SRB, and later releases,
support for continue clauses for outbound route maps was introduced.
Route Map Operation Without Continue Clauses

A route map evaluates match clauses until a successful match occurs. After
the match occurs, the route map stops evaluating match clauses and starts
executing set clauses, in the order in which they were configured. If a
successful match does not occur, the route map "falls through" and evaluates
the next sequence number of the route map until all configured route map
entries have been evaluated or a successful match occurs. Each route map
sequence is tagged with a sequence number to identify the entry. Route map
entries are evaluated in order starting with the lowest sequence number and
ending with the highest sequence number. If the route map contains only set
clauses, the set clauses will be executed automatically, and the route map
will not evaluate any other route map entries.
Route Map Operation with Continue Clauses

When a continue clause is configured, the route map will continue to
evaluate and execute match clauses in the specified route map entry after a
successful match occurs. The continue clause can be configured to go to (or
jump to) a specific route map entry by specifying the sequence number, or if
a sequence number is not specified, the continue clause will go to the next
sequence number. This behavior is called an "implied continue." If a match
clause exists, the continue clause is executed only if a match occurs. If no
successful matches occur, the continue clause is ignored.
Match Operations with Continue Clauses

If a match clause does not exist in the route map entry but a continue
clause does, the continue clause will be automatically executed and go to
the specified route map entry. If a match clause exists in a route map
entry, the continue clause is executed only when a successful match occurs.
When a successful match occurs and a continue clause exists, the route map
executes the set clauses and then goes to the specified route map entry. If
the next route map entry contains a continue clause, the route map will
execute the continue clause if a successful match occurs. If a continue
clause does not exist in the next route map entry, the route map will be
evaluated normally. If a continue clause exists in the next route map entry
but a match does not occur, the route map will not continue and will "fall
through" to the next sequence number if one exists.
Set Operations with Continue Clauses

Set clauses are saved during the match clause evaluation process and
executed after the route-map evaluation is completed. The set clauses are
evaluated and executed in the order in which they were configured. Set
clauses are executed only after a successful match occurs, unless the route
map does not contain a match clause. The continue statement proceeds to the
specified route map entry only after configured set actions are performed.
If a set action occurs in the first route map and then the same set action
occurs again, with a different value, in a subsequent route map entry, the
last set action may override any previous set actions that were configured
with the same set command unless the set command permits more than one
value. For example, the set as-path prepend command permits more than one
autonomous system number to be configured.

http://www.cisco.com/en/US/docs/ios/12_4t/ip_route/configuration/guide/t_brbext.html#wp1061585

On Sat, Aug 29, 2009 at 7:20 PM, S Malik <ccie.09_at_gmail.com> wrote:

> Natraajan,
> you are correct, ACL & Prefix-list under same clause don't go together.
> Please see following link quoting example and I wrongly understood AND/OR
> logic from there,
>
>
> http://books.google.com/books?id=-SM1Jeu07UYC&pg=RA1-PA273&lpg=RA1-PA273&dq=r
>
> oute-map+logical+AND&source=bl&ots=w8TcsNnJHf&sig=jvVGIhjeOBFS6njdfBjFzn4cnyY
>
> &hl=en&ei=fDGZSs_kAcuf8Qau8uSfBQ&sa=X&oi=book_result&ct=result&resnum=2#v=one
> page&q=route-map%20logical%20AND&f=false
>
>
> On Sat, Aug 29, 2009 at 9:28 AM, Anantha Subramanian Natarajan <
> anantha.natarajan_at_gravitant.com> wrote:
>
> > Hi Scott,
> >
> > If I understand properly from you ,I tried that,it give an error
> > mentioning u can't use the prefix-list and access-list on the same
> route-map
> > sequence as below
> >
> > *"% prefix-list and access-list can not co-exist in one route-map
> > sequence"*
> >
> > Thanks
> >
> > Regards
> > Anantha Subramanian Natraajan
> >
> > On Sat, Aug 29, 2009 at 8:25 AM, Scott Morris <smorris_at_ine.com> wrote:
> >
> >> If they're the same TYPE (e.g. two ACLs) then the router will redo
> things
> >> for you onto the same line, making the logic an OR. Kind of obnoxious
> if
> >> you ask me. :)
> >>
> >> But if you do two DIFFERENT things (e.g. one prefix list and one ACL)
> you
> >> can have the AND logic working.
> >>
> >>
> >>
> >>
> >> *Scott Morris*, CCIE*x4* (R&S/ISP-Dial/Security/Service Provider) #4713,
> >>
> >> JNCIE-M #153, JNCIS-ER, CISSP, et al.
> >>
> >> JNCI-M, JNCI-ER
> >>
> >> evil_at_ine.com
> >>
> >>
> >> Internetwork Expert, Inc.
> >>
> >> http://www.InternetworkExpert.com <http://www.internetworkexpert.com/>
> >>
> >> Toll Free: 877-224-8987
> >>
> >> Outside US: 775-826-4344
> >>
> >>
> >> Knowledge is power.
> >>
> >> Power corrupts.
> >>
> >> Study hard and be Eeeeviiiil......
> >>
> >>
> >>
> >>
> >> S Malik wrote:
> >>
> >> One thing is sure that same line is O, when we assign two ACL under one
> >> clause, it is shown in one line and treated as OR.
> >>
> >> On Sat, Aug 29, 2009 at 7:53 AM, Anantha Subramanian Natarajan
> <anantha.natarajan_at_gravitant.com> wrote:
> >>
> >>
> >>
> >> Hi Sugar Can,
> >>
> >> Can you try inside the route-map as below
> >>
> >> Match ip address prefix-list <prefix-list1><prefix-list2>
> >>
> >> I think whenever we specify the match criteria on same line ,it is an
> AND
> >> operation
> >>
> >> Regards
> >> Anantha Subramanian Natarajan
> >>
> >> On Sat, Aug 29, 2009 at 12:57 AM, Sagar Rane <sagar.ccie_at_gmail.com>
> <sagar.ccie_at_gmail.com> wrote:
> >>
> >>
> >>
> >> Hi All,
> >>
> >> I have requirement where, bgp should check its bgp routing table for two
> >> routes eq (10.1.1.0/24 and 20.2.2.2/32) and only if both routes are
> >> present,
> >> it should originate a route advertisement of 192.168.10.0/24.
> >>
> >> I have tried advertise-map and exist map, but how can we used exist-map
> >>
> >>
> >> to
> >>
> >>
> >> check both the routes at the same time?
> >>
> >> Anyway how we can meet this requirement please let me know.
> >>
> >> Regards,
> >> Sagar
> >>
> >>
> >> Blogs and organic groups at http://www.ccie.net
> >>
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