Re: OSPF conditional default route injection

*Lets say you have the following topology:*

*R1 (F0/0)---------- (F0/0) R2 (F0/1)-------------(F0/1) R3*

* *

*IP addressing:*

*R1s F0/0 = 10.1.12.1 /24*

*R2s F0/0 = 10.1.12.2 /24*

*R2s F0/1 = 10.1.23.2 /24*

*R3s F0/1 = 10.1.23.3 /24*

*R3s Loopback0 = 3.3.3.3 /24*

* *

*Routing protocols:*

*R1 and R2 are running OSPF in area 0*

* *

*R2 and R3 are running Eigrp As 100, R3s Loopback0 interface is advertised
in this routing protocol.*

*Policy:*

*R2 should inject a default route ONLY if it does NOT see network 3.3.3.0
/24 in its routing table:*

*On R2*

*router ospf 1*

*network 10.1.12.2 0.0.0.0 area 0*

*default-information originate*

*We know that default-information originate on its own will NOT inject a
default route, and we need a default route in order to originate one. Lets
configure one:*

R2(config)#*ip route 0.0.0.0 0.0.0.0 Null0*

*We should see a default route injected in R1s routing table:*

*R1#Show ip route ospf | Inc O*

* *

*O*E2 0.0.0.0/0 [110/1] via 10.1.12.2, **00:08:09**, FastEthernet0/0*

*Now lets implement the policy:*

*The state of the following Boolean will ONLY be UP, if object 1 is NOT up
(Specified by the NOT keyword in the second line of the following
configuration):*

R2(config)#*track 3 list boolean and*

R2(config -track)#*object 1 NOT*

*But the question is, what is object 1? So lets define object 1:*

 R2(config)#*track 1 ip route 3.3.3.0 255.255.255.0 reachability*

* *

*In the last step, the Boolean is applied to the static route:*

* *

* *R2(config)#*ip route 0.0.0.0 0.0.0.0 Null0* *Track 3*

*Now lets test:*

*On R1*

R1#Show ip route ospf | Inc O

R1#

*Note R1 does NOT have a default route anymore because R2 can see network
3.3.3.0 /24 in its routing table, here is the proof:*

*On R2*

*R2#Show ip route | B Gate*

Gateway of last resort is not set

     3.0.0.0/24 is subnetted, 1 subnets

*D 3.3.3.0 [90/156160] via 10.1.23.3, **00:01:56**, FastEthernet0/1*

     10.0.0.0/24 is subnetted, 2 subnets

C 10.1.12.0 is directly connected, FastEthernet0/0

C 10.1.23.0 is directly connected, FastEthernet0/1

*So lets shutdown the loopback0 interface on R3 and see the result:*

*On R3*

R3(config)#*Int lo0*

R3(config-if)#*Shut*

*Lets check the routing table on R1:*

*On R1*

*BB1#Show ip route ospf*

* *

*O*E2 0.0.0.0/0 [110/1] via 10.1.12.2, **00:01:07**, FastEthernet0/0*

On Wed, Jun 9, 2010 at 9:34 AM, Narbik Kocharians <narbikk_at_gmail.com> wrote:

> I should add the following:
>
> On R2
> R2(config)#ip route 0.0.0.0 0.0.0.0 null0 track3
>
> On Wed, Jun 9, 2010 at 9:33 AM, <ccie_at_halawlaw.com> wrote:
>
>> Where did you apply the track??
>>
>> On Wed, 9 Jun 2010 09:18:19 -0700, Narbik Kocharians <narbikk_at_gmail.com>
>> wrote:
>> > *Here you go my friend:*
>> > **
>> > *Let s say you have the following topology:*
>> >
>> >
>> >
>> > *R1 (F0/0)---------- (F0/0) R2 (F0/1)-------------(F0/1) R3*
>> >
>> > * *
>> >
>> > *IP addressing:*
>> >
>> > *R1 s F0/0 = 10.1.12.1 /24*
>> >
>> > *R2 s F0/0 = 10.1.12.2 /24*
>> >
>> > *R2 s F0/1 = 10.1.23.2 /24*
>> >
>> > *R3 s F0/1 = 10.1.23.3 /24*
>> >
>> > *R3 s Loopback0 = 3.3.3.3 /24*
>> >
>> > * *
>> >
>> > *Routing protocols:*
>> >
>> > *R1 and R2 are running OSPF in area 0*
>> >
>> > * *
>> >
>> > *R2 and R3 are running Eigrp As 100, R3 s Loopback0 interface is
>> advertised
>> > in this routing protocol.*
>> >
>> >
>> >
>> > *Policy:*
>> >
>> > *R2 should inject a default route ONLY if it does NOT see network
>> 3.3.3.0
>> > /24 in its routing table:*
>> >
>> >
>> >
>> > *On R2*
>> >
>> >
>> >
>> > *router ospf 1*
>> >
>> > *network 10.1.12.2 0.0.0.0 area 0*
>> >
>> > *default-information originate*
>> >
>> >
>> >
>> > *We know that default-information originate on its own will NOT inject a
>> > default route, and we need a default route in order to originate one.
>> Let s
>> > configure one:*
>> >
>> >
>> >
>> > R2(config)#*ip route 0.0.0.0 0.0.0.0 Null0*
>> >
>> >
>> >
>> > *We should see a default route injected in R1 s routing table:*
>> >
>> >
>> >
>> > *R1#Show ip route ospf | Inc O*
>> >
>> > * *
>> >
>> > *O*E2 0.0.0.0/0 [110/1] via 10.1.12.2, **00:08:09**, FastEthernet0/0*
>> >
>> >
>> >
>> > *Now let s implement the policy:*
>> >
>> >
>> >
>> > *The state of the following Boolean will ONLY be UP, if object 1 is NOT
>> up
>> > (Specified by the NOT keyword in the second line of the following
>> > configuration):*
>> >
>> >
>> >
>> > R2(config)#*track 3 list boolean and*
>> >
>> > R2(config -track)#*object 1 NOT*
>> >
>> >
>> >
>> > *But the question is, what is object 1? So let s define object 1:*
>> >
>> >
>> >
>> > R2(config)#*track 1 ip route 3.3.3.0 255.255.255.0 reachability*
>> >
>> >
>> >
>> > *Now let s test:*
>> >
>> >
>> >
>> > *On R1*
>> >
>> >
>> >
>> > R1#Show ip route ospf | Inc O
>> >
>> > R1#
>> >
>> >
>> >
>> > *Note R1 does NOT have a default route anymore because R2 can see
>> network
>> > 3.3.3.0 /24 in its routing table, here is the proof:*
>> >
>> >
>> >
>> > *On R2*
>> >
>> >
>> >
>> > *R2#Show ip route | B Gate*
>> >
>> > Gateway of last resort is not set
>> >
>> >
>> >
>> > 3.0.0.0/24 is subnetted, 1 subnets
>> >
>> > *D 3.3.3.0 [90/156160] via 10.1.23.3, **00:01:56**,
>> FastEthernet0/1*
>> >
>> > 10.0.0.0/24 is subnetted, 2 subnets
>> >
>> > C 10.1.12.0 is directly connected, FastEthernet0/0
>> >
>> > C 10.1.23.0 is directly connected, FastEthernet0/1
>> >
>> >
>> >
>> > *So let s shutdown the loopback0 interface on R3 and see the result:*
>> >
>> >
>> >
>> > *On R3*
>> >
>> >
>> >
>> > R3(config)#*Int lo0*
>> >
>> > R3(config-if)#*Shut*
>> >
>> >
>> >
>> > *Let s check the routing table on R1:*
>> >
>> >
>> >
>> > *On R1*
>> >
>> >
>> >
>> > *BB1#Show ip route ospf*
>> >
>> > * *
>> >
>> > *O*E2 0.0.0.0/0 [110/1] via 10.1.12.2, **00:01:07**, FastEthernet0/0*
>> >
>> >
>> > On Wed, Jun 9, 2010 at 8:03 AM, Sorin Platon <sorin.platon_at_gmail.com>
>> > wrote:
>> >
>> >> So i tried tested and labed the OSPF conditional default route
>> injection,
>> >> all the scenarios i did were to inject a default route based on the
>> >> presence
>> >> of a subnet in the routing table
>> >>
>> >> This was done trough route-maps or reliable static routes
>> >>
>> >> I'm trying to do the reverse, inject a default route in case a subnet
>> is
>> >> NOT
>> >> present in the routing table
>> >>
>> >> I did tried the obvious and did a deny on the ACL or a deny in the
>> >> routing
>> >> map but didn't got the desired result
>> >>
>> >> is it feasible ?
>> >>
>> >> regards
>> >> Sorin
>> >>
>> >>
>> >> Blogs and organic groups at http://www.ccie.net
>> >>
>> >> _______________________________________________________________________
>> >> Subscription information may be found at:
>> >> http://www.groupstudy.com/list/CCIELab.html
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>> >
>> > --
>> > Narbik Kocharians
>> > CCSI#30832, CCIE# 12410 (R&S, SP, Security)
>> > www.MicronicsTraining.com <http://www.micronicstraining.com/>
>> > Sr. Technical Instructor
>> > YES! We take Cisco Learning Credits!
>> > Training And Remote Racks available
>> >
>> >
>> > Blogs and organic groups at http://www.ccie.net
>> >
>> > _______________________________________________________________________
>> > Subscription information may be found at:
>> > http://www.groupstudy.com/list/CCIELab.html
>>
>
>
>
> --
> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> www.MicronicsTraining.com <http://www.micronicstraining.com/>
> Sr. Technical Instructor
> YES! We take Cisco Learning Credits!
> Training And Remote Racks available
>

--
Narbik Kocharians
CCSI#30832, CCIE# 12410 (R&S, SP, Security)
www.MicronicsTraining.com
Sr. Technical Instructor
YES! We take Cisco Learning Credits!
Training And Remote Racks available
Blogs and organic groups at http://www.ccie.net