default-route redi issue on ospf

syjeon · ‎07-04-2010

Greeting.

We knew that,

if we advertise default-route to all ospf domain, we should confiigure 'ospf default-information originate' in ospf process.

However,

but some ios, or version, We can do as following to advertise ospf default-route.

ip route 0.0.0.0 0.0.0.0 x.x.x.x(next-hop)

!

router ospf 1

redistribute static subnet

!

we can see default-route in RIB on another ospf router.

but some ios, even if we configure above, we can't see the default-route 0.0.0.0 on RIB on another same ospf domain

in this case, we should configure ' default-information originate' on ospf router.

What is the difference of redi static subnet(default-route 0.0.0.0) and default-information originate.

Finally, Can I advertise default-route to another ospf process using with 'ospf default-information' in spite of configuring redi static subnet?

Ganesh Hariharan · ‎07-05-2010

Greeting.
We knew that,
 if we advertise default-route to all ospf domain, we should confiigure 'ospf default-information originate' in ospf process.
However,
 but some ios, or version, We can do as following to advertise ospf default-route.
 ip route 0.0.0.0 0.0.0.0 x.x.x.x(next-hop)
 !
 router ospf 1
 redistribute static subnet
 !
we can see default-route in RIB on another ospf router.
but some ios, even if we configure above, we can't see the default-route 0.0.0.0 on RIB on another same ospf domain
in this case, we should configure ' default-information originate' on ospf router.
What is the difference of redi static subnet(default-route 0.0.0.0) and default-information originate.
Finally,
Can I advertise default-route to another ospf process using with 'ospf
default-information' in spite of configuring redi static subnet?

Hi,

The default routes created using the ip route 0.0.0.0 0.0.0.0 command are not propagated by OSPF and IS-IS. Additionally, this default cannot be redistributed into OSPF or IS-IS using the redistribute command. Use the default-information originate command to generate a default route into an IS-IS or OSPF routing domain.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094374.shtml

Hope to Help !!

Ganesh.H

Remember to rate the helpful post

syjeon · ‎07-06-2010

Thank for your comment.

but That's some strange.

Device A has default-route and redis sub net on ospf 1. as following :

Device_A(x.x.x.141)
router ospf 1
log-adjacency-changes
redistribute static subnets ( there is no default-information originate )
!
!
ip route 0.0.0.0 0.0.0.0 x.x.x.x

but device B received default-route from device A.
Device_B
LUS_Device#show ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "ospf 1", distance 110, metric 1, candidate default path
Tag 1, type extern 2, forward metric 2
Last update from x.x.x.44 on FastEthernet1/0/48, 2w1d ago
Routing Descriptor Blocks:
* x.x.x.141, from x.x.x.44, 2w1d ago, via FastEthernet1/0/48
Route metric is 1, traffic share count is 1
Route tag 1

both device IOS ver.
* 1 52 WS-C3750-48TS 12.2(35)SE5 C3750-IPSERVICESK9-M

Could you check me up?. Is It a IOS bug?

Hitesh Vinzoda · ‎07-06-2010

Hi,

When you redistribut static routes in OSPF, it checkes the static route installed in routing table and picks up all installed static routes and redistribute them in OSPF doesnt matter if it was a default route configured statically ok so whats the difference between resdistibuting static routes and default information originate command

for example if there were more static routes configured and you just wanted to have default advertised, you have to use route-map to filter out other routes than default, while if you use default information originate it only looks for any default route installed in routing table or not, if its there than it will advertize the default route... simply

HTH

Hitesh Vinzoda

Pls rate useful posts

Edison Ortiz · ‎07-06-2010

When you redistribut static routes in OSPF, it checkes the static route 
installed in routing table and picks up all installed static routes and 
redistribute them in OSPF doesnt matter if it was a default route 
configured

Incorrect. It will bring all static routes into OSPF with the exception of the default route.

Hitesh Vinzoda · ‎07-06-2010

Hey Edison,

Thanks for pointing out the odd, I need to revisit the docs ..

Regards

Hitesh Vinzoda

Edison Ortiz · ‎07-06-2010

It's this a normal OSPF area or a stub/nssa area?

What you are seeing it's not normal under a normal OSPF area, please refer to this document for more info:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a74.shtml

Can you provide information from typing show ip os data external

Regards,

Edison