Solved: Re: Packet tracer OSPF issue

thajiyev9 · ‎01-01-2018

Hello!

I have an issue about OSPF in packet tracer. I upload my topology. There are 5 router in my network and R4 connected to R5(ISP). So that, I have default route to isp and originate it in ospf. R2 get this default route with 2 different way. When i ping from R1 to R5, if R2 using route via 10.10.12.0, it cause problem. I dont want default route via 10.10.12.1, only want to use 10.10.24.4. Changing bandwith and ospf cost didnt change anything.
Edit:
English is not my mother tongue, so I apologize for writing mistakes.

Julio E. Moisa · ‎01-01-2018

Hi

Please correct me if Im understanding wrong but you want to prefer the path from R1 through R3 instead R2?

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

View solution in original post

Georg Pauwen · ‎01-01-2018

Hello,

the problem is that Packet Tracer does not really simulate 'real' IOS devices, but rather executes a number of commands and displays pre-programmed results.

If you lab this is e.g. GNS3, your router R4 would not even generate a default route (to R2 and R3) because there is no default route existing in the routing table. You would need to add the 'always' keyword to the 'default-information originate' command for the default route to be installed regardless of its existence in the routing table. Also, having to paths is not happening in a real network. I don't know why Packet Tracer installs both default routes.

Conclusion: forget about it and lab this in GNS3 to get more reliable results.

View solution in original post

Julio E. Moisa · ‎01-01-2018

Hi

It looks like a bug on the PT, if you verify the routing table on R2 it shows the same metrics for both default routes and from R1's perspective it learns one of the 2 paths until you execute: show ip ospf process <yes>.

I changed the area number to zero and it fixed the trouble, probably it is related with multi-areas on packet tracer.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

View solution in original post

Julio E. Moisa · ‎01-01-2018

Hi

You are welcome :-)

Yes it could be a bug on PT.

Have a great new year.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

View solution in original post

Julio E. Moisa · ‎01-01-2018

Hi

Please correct me if Im understanding wrong but you want to prefer the path from R1 through R3 instead R2?

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

Yeah, it is true.

Julio E. Moisa · ‎01-01-2018

Hi

It can depend of the cost, try configuring the following cost under the link between R1 and R2:

ip ospf cost 20000

And try in few seconds again. The trafic should go through: R1 ---> R3 ---> R4 ---> R5

:-)

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

Hi,

Sorry, but it did not change anything. Both of them are in routing table.

Julio E. Moisa · ‎01-01-2018

Ok

Have you verified if the path is being known through R3? You can shutdown the R1's interface facing to R2 and try again.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

I shutdown R1, gig0/0 interface and default route via 10.10.12.0 disappear.

Julio E. Moisa · ‎01-01-2018

Ok, are you able to go through R3, R4 and R5?

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

Before i shutdown R1's interface facing to R2 the same issue happened in R3 ( via 10.10.13.1 ) but when i shutdown interface, 10.10.13.1 disappear and all ping were success. Then i up interface and the same issue appeared.

Julio E. Moisa · ‎01-01-2018

Hi

Could you please share the configuration of each router? it could be paste here or attaching a notepad.

Thank you in advance.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

May i send you my pkt file?

Julio E. Moisa · ‎01-01-2018

Hi,

Yes but I think that file cannot be attached. Please let me share a configuration based on your topology.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

Julio E. Moisa · ‎01-01-2018

R1

conf t

int fa0/0

description TO-R2

ip add 10.0.12.1 255.255.255.0

no shutdown

int fa0/1

description TO-R3

ip add 10.0.13.1 255.255.255.0

no shutdown

router ospf 1

net 10.0.12.1 0.0.0.0 area 0

net 10.0.13.1 0.0.0.0 area 0

R2

conf t

int fa0/0

description TO-R1

ip add 10.0.12.2 255.255.255.0

no shutdown

int fa0/1

description TO-R4

ip add 10.0.24.2 255.255.255.0

no shutdown

router ospf 1

net 10.0.12.2 0.0.0.0 area 0

net 10.0.24.2 0.0.0.0 area 0

R3

conf t

int fa0/0

description TO-R1

ip add 10.0.13.3 255.255.255.0

no shutdown

int fa0/1

description TO-R4

ip add 10.0.34.3 255.255.255.0

no shutdown

router ospf 1

net 10.0.13.3 0.0.0.0 area 0

net 10.0.34.3 0.0.0.0 area 0

R4

conf t

int fa0/0

description TO-R2

ip add 10.0.24.4 255.255.255.0

no shutdown

int fa0/1

description TO-R3

ip add 10.0.34.4 255.255.255.0

no shutdown

int fa0/2

description TO-R5

ip add 10.0.45.4 255.255.255.0

no shutdown

router ospf 1

net 10.0.34.4 0.0.0.0 area 0

net 10.0.24.4 0.0.0.0 area 0

net 10.0.45.4 0.0.0.0 area 0

R5

interface loopback 0

ip add 5.5.5.5 255.255.255.255

conf t

int fa0/0

description TO-R4

ip add 10.0.45.5 255.255.255.0

no shutdown

router ospf 1

net 10.0.45.5 0.0.0.0 area 0

net 5.5.5.5 0.0.0.0 area 0

You should have something like that configuration, R1 will have 2 equal cost path to R5's loopback. You could configure higher cost between R1 and R2 to move the traffic to R3.

:-)

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

thajiyev9 · ‎01-01-2018

R5 dont use ospf. I design as R5 is ISP and R4 have static route to R5. Then i originate this static route with ospf.

R4

ip route 0.0.0.0 0.0.0.0 10.10.45.5

(router mode)

default-information originate

thajiyev9 · ‎01-01-2018

R1

conf t

int fa0/0

ip add 10.10.12.1 255.255.255.0

no shutdown

int fa0/2

ip add 10.10.13.1 255.255.255.0

no shutdown
cost 100

router ospf 1

net 10.10.12.1 0.0.0.0 area 0

net 10.10.13.1 0.0.0.0 area 0

R2

conf t

int fa0/0

ip add 10.10.12.2 255.255.255.0

no shutdown

int fa0/1

ip add 10.10.24.2 255.255.255.0

no shutdown

router ospf 1

net 10.10.12.2 0.0.0.0 area 0

net 10.10.24.2 0.0.0.0 area 1

R3

conf t

int fa0/2

ip add 10.10.13.3 255.255.255.0

no shutdown

int fa0/1

ip add 10.10.34.3 255.255.255.0

no shutdown

router ospf 1

net 10.10.13.3 0.0.0.0 area 0

net 10.10.34.3 0.0.0.0 area 1

R4

conf t

ip route 0.0.0.0 0.0.0.0 10.10.45.5

int fa0/0

ip add 10.10.24.4 255.255.255.0

no shutdown

int fa0/1

ip add 10.10.34.4 255.255.255.0

no shutdown

int fa0/2

ip add 10.10.45.4 255.255.255.0

no shutdown

router ospf 1

net 10.10.34.4 0.0.0.0 area 1

net 10.10.24.4 0.0.0.0 area 1

passive-interface gig 0/2(faced to R5)

default-information originate

R5

conf t

int fa0/0

ip add 10.10.45.5 255.255.255.0

no shutdown