Default-information originate vs Default-information originate always

Oke, the #default-information originate command is used to advertise and default route to other OSPF router in area, but with the always command this somehow is forced?? So how and based on what will the router originate a defualte route?? Pointing to itself??

I'm having trouble wiht grasping the difference between them.

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networker050184

The 'always' knob allows the router to advertise a default route even if there is not one in the routing table.

FrankGuthrie

networker050184 wrote: »

The 'always' knob allows the router to advertise a default route even if there is not one in the routing table.

I have ssen this written on the internet, but it doesn't register with me

So if you use #default-information originate, the router is going to REdistribute a default route it got from another Router, and with the default-information originate always command the Router will generate default route pointing to itself?? Did I under this correctly.

networker050184

If you do not use 'always' the router only advertises a default route if it has one in its own routing table. Either way the default route sent into OSPF is the same though.

xXErebuS

FrankGuthrie wrote: »

I have ssen this written on the internet, but it doesn't register with me

So if you use #default-information originate, the router is going to REdistribute a default route it got from another Router, and with the default-information originate always command the Router will generate default route pointing to itself?? Did I under this correctly.

Almost correct - the default-information originate will redistribute any default route whether it be from another router or if you create a static default route on itself - it can even be from a different routing protocol but it has to be present in the routing table.

Note that the always command still shows up as a O*E2 so technically it redistributes a default route pointing to itself.

FrankGuthrie

xXErebuS wrote: »

Almost correct - the default-information originate will redistribute any default route whether it be from another router or if you create a static default route on itself - it can even be from a different routing protocol but it has to be present in the routing table.

Note that the always command still shows up as a O*E2 so technically it redistributes a default route pointing to itself.

Even from a different protocol..... interesting. All the awnsers given helped me with my doubts, thanks guys

. This is now clear.

So to sum up, if I get a default route from another Router, via a Dynamic Routing Protocol (meaning it's in the Routing table) or I have issued the (config)#ip route 0.0.0.0 0.0.0.0 X.X.X.X command and I issues the (config-router)#default-information originate command this will (re)advertise the default route to downstream Routers.

If I have not issued the (config)#ip route 0.0.0.0 0.0.0.0 X.X.X.X command or learned a default route from a Dynamic Routing Protocol, and i want to advertise a default route I can use the (config-router)#default-information originate always to automatically generate a default route pointing to that Router, which then will be advertised downstream.

Correct? I think i got it

networker050184

Correct. Most of the time the always is going to be used unless you want a conditional default route. No point in having the default route advertised and withdrawn if the router is the only gateway out.

FrankGuthrie

@networker050184

Thanks