Difference between Default-originate and network 0.0.0.0 in BGP

[turbo_engine26]

Hello,

Please i need someone to clarify what is the difference between the

"default-originate" command and "network 0.0.0.0 - ip route 0.0.0.0 0.0.0.0 null0" commands. 

I see both are serving the same purpose by advertising a default route to a peer but in the same time i feel a difference on them.

Thx

Regards,

A.M.

[davinci]

Peter, can you explain a scenario where you would use a

route map with the neighbor X.X.X.X default-originate?

[Georg Pauwen]

Hello,

take the example below.

The default route to neighbor 10.10.10.2 is injected only if there is a route to 192.168.1.0.

access-list 1 permit 192.168.1.0
!
route-map DEFAULT 10 permit
match ip address 1
!
router bgp 1
network 10.0.0.0 mask 255.0.0.0
neighbor 10.10.10.2 remote-as 2
neighbor 10.10.10.2 default-originate route-map DEFAULT

[ChrisNewnham_]

Hello @Peter Paluch ,

You said:

• default-information originate

  causes the default route to be artificially generated and injected into the BGP RIB, regardlessly of whether it is present in the routing table.

But I believe this is not true - default-information originate requires the default route to be redistributed? It will not artificially generate the default route I believe?

Thanks!

[MHM Cisco World]

Make new post it better

And ask your Q 

This make many answer you and you can more clarify the best answer for you 

MHM

[Harold Ritter]

Hi @ChrisNewnham_ ,

These are two different commands that are often mistaken.

router bgp xxx

address-family ipv4 unicast

neighbor x.x.x.x default-originate

!

router bgp xxx

address-family ipv4 unicast 

default-information originate

When you use the "neighbor x.x.x.x default-originate", it will as mentioned in this post advertise a default route to the neighbor, regardless if the default route is present in the routing table or not.

The other command "default-information originate" configured lets say under "address-family ipv4 unicast". In this case, this will allow redistribution of the default route from any protocol into BGP. Without this command the default route would not be redistributed into BGP. The default route would definitely need to be present in the routing table in order to be redistributed into BGP. 

Regards,

[Uttkap]

Hi,

Thanks for the information, but i still have a little doubt, what is the difference between

default-information originate and default-information originate always ???

[Uttkap]

Adding 1 more question to this question ::

Hi,

what is the difference between

default-information originate and default-information originate always ???

[Bo Urskov]

Hi Uttkap...

There is no such command in

BGP - default-information originate always"... this is for OSPF...

In OSPF the

default-information originate

will advertise a default route when such a route is present in the RIB

default-information originate always

will make the router advertise a default route regardless of the presence of a default route in the router - hence it ALWAYS originates a default route...