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RE: Ccie R&S lab 3 questions for the list.... posted 09/28/2004
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	Yes, route-maps have an implicit deny at the end of them like
access-lists, but that doesn't relate to BGP dampening.  

	When BGP dampening is configured with the route-map option, only
sequences that have the "set dampening" option configured will have
dampening applied.  Sequences that do not have this option will not have
default dampening parameters applied, regardless if the sequence says
permit or deny.

	For example, look at the output when dampening is configured
without a route-map:

router bgp 200
 bgp dampening

Rack4R1#show ip bgp dampening parameters 
 dampening 15 750 2000 60 (DEFAULT)
  Half-life time      : 15 mins       Decay Time       : 2320 secs
  Max suppress penalty: 12000         Max suppress time: 60 mins
  Suppress penalty    :  2000         Reuse penalty    : 750

	The "show ip bgp dampening parameters" output dictates the
default dampening options for all prefixes.  Now look at what happens
when a route-map is applied:

router bgp 200
 bgp dampening route-map DAMPENING
!
ip prefix-list 222.22.2.0 seq 5 permit 222.22.2.0/24
!
route-map DAMPENING permit 10
 match ip address prefix-list 222.22.2.0
 set dampening 15 750 2000 60
!
route-map DAMPENING permit 20

Rack4R1#show ip bgp dampening parameters 
 dampening 15 750 2000 60 (route-map DAMPENING 10)
  Half-life time      : 15 mins       Decay Time       : 2320 secs
  Max suppress penalty: 12000         Max suppress time: 60 mins
  Suppress penalty    :  2000         Reuse penalty    : 750

	Note that the "show ip bgp dampening parameters" only lists the
parameters defined in sequence 10 of route-map DAMPENING.  Even though
sequence 20 is explicit permit, there are no dampening parameters
defined, hence no other routes besides 222.22.2.0/24 will be dampened.



HTH,

Brian McGahan, CCIE #8593
bmcgahan@xxxxxxxxxxxxxxxxxxxxxx 

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> -----Original Message-----
> From: James [mailto:james@xxxxxxxxxxxx]
> Sent: Tuesday, September 28, 2004 3:49 PM
> To: Edwards, Andrew M
> Cc: Brian McGahan; Matt; ccielab@xxxxxxxxxxxxxx
> Subject: Re: Ccie R&S lab 3 questions for the list....
> 
> On Tue, Sep 28, 2004 at 01:39:33PM -0700, Edwards, Andrew M wrote:
> > Then, if I were only asked to dampen ONE route, and I match it with
the
> > first sequence of the route-map, I wouldn't need an additional
sequence
> > because I have no other routes I want to dampen... True?
> 
> Correct. route-maps are implicit deny.
> 
> -J
> 
> >
> >
> > -----Original Message-----
> > From: Brian McGahan [mailto:bmcgahan@xxxxxxxxxxxxxxxxxxxxxx]
> > Sent: Tuesday, September 28, 2004 11:53 AM
> > To: Matt; ccielab@xxxxxxxxxxxxxx
> > Subject: RE: Ccie R&S lab 3 questions for the list....
> >
> >
> > Matt,
> >
> > 	Dampening is applied on the router itself not on a specific
> > peering.  This is why it doesn't relate to what it advertised.  When
you
> > call your route-map you need to call it like this:
> >
> > router bgp 1
> >  bgp dampening route-map DAMPEN
> >
> > 	If you then want to filter what is advertised to a specific peer
> > create another route-map for that purpose and apply it to the peer.
> >
> >
> > HTH,
> >
> > Brian McGahan, CCIE #8593
> > bmcgahan@xxxxxxxxxxxxxxxxxxxxxx
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> > 24/7 Support: http://forum.internetworkexpert.com
> > Live Chat: http://www.internetworkexpert.com/chat/
> >
> >
> > > -----Original Message-----
> > > From: Matt [mailto:matt_ccie_2004@xxxxxxxxx]
> > > Sent: Tuesday, September 28, 2004 1:41 PM
> > > To: Brian McGahan
> > > Subject: RE: Ccie R&S lab 3 questions for the list....
> > >
> > > Actually,   maybe I am missing something here.
> > >
> > > R1 is advertising 3 /32 routes to R3:
> > >
> > > R3#sh ip bgp
> > > BGP table version is 4, local router ID is 1.1.1.2
> > > Status codes: s suppressed, d damped, h history, *
> > > valid, > best, i - internal,
> > >               r RIB-failure, S Stale
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > >
> > >    Network          Next Hop            Metric LocPrf
> > > Weight Path
> > > *> 1.1.1.1/32       10.1.1.1                 0
> > >     0 1 i
> > > *> 2.2.2.2/32       10.1.1.1                 0
> > >     0 1 i
> > > *> 3.3.3.3/32       10.1.1.1                 0
> > >     0 1 i
> > > R3#
> > >
> > > now when i add the following route-map to that
> > > peering:
> > > route-map dampen permit 10
> > >  match ip address prefix-list Dampen
> > >  set dampening 2 15 15 2
> > >
> > > ip prefix-list Dampen seq 5 permit 1.1.1.1/32
> > >
> > > R3(config)#router bgp 2
> > > R3(config-router)#neigh 10.1.1.1 route-map dampen in
> > > % "dampen" used as BGP inbound route-map, set
> > > dampening not supported
> > > R3(config-router)#^Z
> > > R3#
> > > 01:44:11: %SYS-5-CONFIG_I: Configured from console by
> > > console
> > > R3#
> > > R3#clear ip bgp * s
> > > R3#sh ip bgp
> > > BGP table version is 6, local router ID is 1.1.1.2
> > > Status codes: s suppressed, d damped, h history, *
> > > valid, > best, i - internal,
> > >               r RIB-failure, S Stale
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > >
> > >    Network          Next Hop            Metric LocPrf
> > > Weight Path
> > > *> 1.1.1.1/32       10.1.1.1                 0
> > >     0 1 i
> > > R3#
> > >
> > > it gives me an error, yet it only allows the route
> > > specified by the prefix list since I do not have a
> > > permit 20 statement.
> > >
> > > thoughts?  (didn't want to spam the whole list with
> > > this)
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > --- Brian McGahan <bmcgahan@xxxxxxxxxxxxxxxxxxxxxx>
> > > wrote:
> > >
> > > > 	Actually this second route-map statement will not
accomplish
> > > > anything, because the routes will not be dampened
> > > > unless specific
> > > > dampening parameters are applied to them.  This is
> > > > not to say that the
> > > > routes will or will not be used or advertised,
> > > > simply that they will not
> > > > be dampened regardless whether the second route-map
> > > > sequence is there or
> > > > not.
> > > >
> > > >
> > > > HTH,
> > > >
> > > > Brian McGahan, CCIE #8593
> > > > bmcgahan@xxxxxxxxxxxxxxxxxxxxxx
> > > >
> > > > Internetwork Expert, Inc.
> > > > http://www.InternetworkExpert.com
> > > > Toll Free: 877-224-8987 x 705
> > > > Outside US: 775-826-4344 x 705
> > > > 24/7 Support: http://forum.internetworkexpert.com
> > > > Live Chat: http://www.internetworkexpert.com/chat/
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: nobody@xxxxxxxxxxxxxx
> > > > [mailto:nobody@xxxxxxxxxxxxxx] On Behalf
> > > > Of
> > > > > Matt
> > > > > Sent: Tuesday, September 28, 2004 11:02 AM
> > > > > To: Edwards, Andrew M; ccielab@xxxxxxxxxxxxxx
> > > > > Subject: Re: Ccie R&S lab 3 questions for the
> > > > list....
> > > > >
> > > > > regarding the second permit statement in the
> > > > dampening
> > > > > route-map...that statement is there to permit
> > > > anything
> > > > > else not specified in the first statement.
> > > > Without
> > > > > it, the rest will be denied.
> > > > >
> > > > > -matt
> > > > >
> > > > > --- "Edwards, Andrew M"
> > > > <andrew.m.edwards@xxxxxxxxxx>
> > > > > wrote:
> > > > >
> > > > > > For those of you familiar with the lab, I'd
> > > > > > appreciate any feedback.
> > > > > > Especially on bgp dampening because I think I
> > > > really
> > > > > > need to get the
> > > > > > purpose of the second route-map permit sequence.
> > > > > > Re:  requirement to not accept routes from any
> > > > other
> > > > > > EIGRP routers on
> > > > > > VLAN 1 that may be added in the future
> > > > > > The author used a distribute list with the
> > > > gateway
> > > > > > statement to allow
> > > > > > only R2 to provide updates to R3 on this VLAN.
> > > > > > I used a different method and wanted to run it
> > > > by
> > > > > > the groupstudy.
> > > > > > I used the distance command such that there were
> > > > two
> > > > > > entries in the
> > > > > > following order:
> > > > > > 1.  distance 90 172.16.0.1 0.0.0.0
> > > > > > 2.  distance 255 172.16.0.0 0.0.255.255
> > > > > >
> > > > > > With this configuration, R3 became adjacent to
> > > > > > another router (I used
> > > > > > the 3550 switch to test) on the VLAN, but DID
> > > > NOT
> > > > > > take any routing
> > > > > > updates from it.
> > > > > > Would this have also met the requiremet from the
> > > > > > lab?  Curious...
> > > > > > re: bgp dampening
> > > > > > I noticed that there were 2 route map sequences
> > > > in
> > > > > > the solution.
> > > > > >
> > > > > > I am not sure what the purpose is to the final
> > > > > > route-map sequence
> > > > > > "permit 20".  Can someone elaborate?
> > > > > >
> > > > > > Generally it was this in Lab 3:
> > > > > >
> > > > > > bgp dampen route-map dampen
> > > > > >
> > > > > > route-map dampen permit 10
> > > > > > match ip add 3
> > > > > > set damp x x x x
> > > > > >
> > > > > > route-map dampen permit 20
> > > > > >
> > > > > > access-list 3 permit ip w.x.y.z 0.0.0.15
> > > > > >
> > > > > > re: bgp rib failures
> > > > > > The author indicates that all the IGP routes
> > > > should
> > > > > > be backdoored for
> > > > > > full points.
> > > > > >
> > > > > > If you only backdoor the peered eBGP neighbor
> > > > > > networks though the routes
> > > > > > will stop flapping and the other routes will
> > > > just be
> > > > > > eBGP instead of
> > > > > > OSPF.
> > > > > >
> > > > > > Is it true, in a lab environment, that we should
> > > > > > ALWAYS set backdoor
> > > > > > routes for IGP learned routes over EGP routes?
> > > > > >
> > > > > > Andy
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
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