Basic OSPF:default-info originate metric-type 1 not showing entry in routing table

Unanswered Question
Mar 9th, 2010

Hi, imagine I have a very simple topology like below. Config for all routers are attached.

R2---R3---R4---R6

On R4, if I do 'router ospf 1 - default-info originate metric-type 1'.I do not see any change I can identify on the routing table of R3, R4 or other routers.

If I do instead 'defaullt-info originate always' then I see the O*E1 0.0.0.0/0 in the routing table - OK. I know the difference between 'always' and the 'metric-type 1' keyword.

If I am doing the option 'default-info originate metric-type 1' any ideas why I do not see anything changing in the routing table indicating that the route is being distributed to other routers? Basically I am trying to test this to assure that it works in a testing envrironment and I can identify the effect of the change.

I have this problem too.
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Giuseppe Larosa Tue, 03/09/2010 - 07:12

Hello Marlon,

>>

On R4, if I do 'router ospf 1 - default-info originate metric-type 1'.I do not see any change I can identify on the routing table of R3, R4 or other routers.

If I do instead 'defaullt-info originate always' then I see the O*E1 0.0.0.0/0 in the routing table - OK. I know the difference between 'always' and the 'metric-type 1' keyword.

there is a default route installed on R4 with any means different from OSPF ?

because always makes the router to generate a default route LSA type  5 in OSPF domain regardless of the presence or not of a default route in IP routing table of R4.

post

R4# sh ip route 0.0.0.0

that is the difference

Hope to help

Giuseppe

news2010a Tue, 03/09/2010 - 07:38

In my case, the R4 is announcing the network to the "ISP router R6" using a dynamic routing protocol, BGP.

My conclusion is that I do not need a default-route since I have BGP running.
That said, that means I do not even benefit at all from such 'default-info originate'  entry in OSPF, correct? So my conclusion is that I should use 'default-info originate' only when there is no dynamic routing available. Is that correct?

R4#show run | s bgp
redistribute bgp 100 metric-type 1 subnets
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.2.0.0 mask 255.255.0.0
network 10.177.206.0 mask 255.255.255.0
aggregate-address 10.2.0.0 255.255.0.0 summary-only
aggregate-address 10.177.206.0 255.255.255.0
neighbor 10.2.47.193 remote-as 200
neighbor 10.2.55.133 remote-as 200
neighbor 10.2.255.15 remote-as 100
neighbor 10.2.255.15 update-source Loopback0
no auto-summary
R4#

Jon Marshall Tue, 03/09/2010 - 09:10

news2010a wrote:

In my case, the R4 is announcing the network to the "ISP router R6" using a dynamic routing protocol, BGP.

My conclusion is that I do not need a default-route since I have BGP running.
That said, that means I do not even benefit at all from such 'default-info originate'  entry in OSPF, correct? So my conclusion is that I should use 'default-info originate' only when there is no dynamic routing available. Is that correct?

R4#show run | s bgp
redistribute bgp 100 metric-type 1 subnets
router bgp 100
no synchronization
bgp log-neighbor-changes
network 10.2.0.0 mask 255.255.0.0
network 10.177.206.0 mask 255.255.255.0
aggregate-address 10.2.0.0 255.255.0.0 summary-only
aggregate-address 10.177.206.0 255.255.255.0
neighbor 10.2.47.193 remote-as 200
neighbor 10.2.55.133 remote-as 200
neighbor 10.2.255.15 remote-as 100
neighbor 10.2.255.15 update-source Loopback0
no auto-summary
R4#

Marlon

You would benefit from using "default-information originate" if you had other OSPF speaking routers that you wanted to receive a default-route. If all your routers are receiving a default-route via BGP or they do not need a default-route then you do not get any benefit from it.

Your conclusion that you should use "default-information originate" only when there is no dynamic routing protocol available is confusing because OSPF is a dynamic routing protocol. Do you mean any other dynamic routing protocol other than OSPF. Even then you may benefit from it if you have routers that only use OSPF.

As for when to the "always" keyword and when not to. Well if you did not have any other routing protocol providing a default-route and you did not have a static default-route the "always" keyword would still allow OSPF to send a default-route to other OSPF speakers. If you miss off the "always" keyword then there has to be a default route supplied to the routers before OSPF would genearate one to other OSPF speaking routers.

Jon

news2010a Tue, 03/09/2010 - 09:39

In my case I have other routers running OSPF. Only the border routers (R4 and R5) are running BGP. Then selected BGP networks will be redistributed into OSPF on R4 and R5.

At least based on this lab, the other internal routers running OSPF were able to learn those routes fine without R4 and R5 (edge routers) using default-information originate.


Sorry for the confusion.

.

Jon Marshall Tue, 03/09/2010 - 10:47

Marlon

At least based on this lab, the other internal routers running OSPF were able to learn those routes fine without R4 and R5 (edge routers) using default-information originate.

The default-information originate only affects the default-route. So any BGP routes you redistribute into OSPF will be fine with or without that statement because they are not the default-route.

Jon

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