Default metric when redistributing the default route into OSPF

[Paheeradan Nagulan]

I was looking at couple of cisco articles and they happened to mention that the default Metric when redistributing the default route from IGP/Static into OSPF is "20". But when I did a LAB in GNS3, it showed me a metric of "1". Which one is accurate?

Here is the output of "show ip ospf database external"

--------------------------------------------------

LS age: 1
Options: (No TOS-capability, DC, Upward)
LS Type: AS External Link
Link State ID: 0.0.0.0 (External Network Number )
Advertising Router: 30.0.0.2
LS Seq Number: 80000006
Checksum: 0x1677
Length: 36
Network Mask: /0
Metric Type: 2 (Larger than any link state path)
MTID: 0
Metric: 1
Forward Address: 0.0.0.0
External Route Tag: 1

[paul driver]

Hello
Apologies but you cannot redistribute a default route into ospf, this is performed via the default-information originate feature in the ospf process.

However for a default route to be entered in the ospf DB the advertising rtr needs to either have a static default route, just like you have mentioned in its route table first or you can "always" advertise a default route using the same command as above but the "always " keyword" appended.

Note -  this default route advertisement even though classed as external route like a redistributed route will not have the same metric cost as that of a redistributed E1/2 route but it will by default perform the same such that an E2 route by default (metric1) or E1 route (metric 2)

[Paheeradan Nagulan]

Hi @paul driver ,

Yes, when I meant redistributing the default route into OSPF, i meant it by issuing the command "default-information originate". Like you said, in my lab I saw E2 with a metric of 1 . So  cisco article I was referring to needs to get updated. Thank you for answering my question!

[MHM Cisco World]

I will check this in lab

MHM

[Flavio Miranda]

@Paheeradan Nagulan 

Are you refering to this?

How your OSPF got the route? Was from BGP? Or is It redistributing to BGP?

"Note: If a metric is not specified, OSPF puts a default value of 20 when it redistributes routes from all protocols except Border Gateway Protocol (BGP) routes, which gets a metric of 1"

[Paheeradan Nagulan]

Hi @Flavio Miranda ,

Here are the answers to your questions.

1)Are you refering to this?

Yes, I was referring to that specific document. 

2)How your OSPF got the route? Was from BGP? Or is It redistributing to BGP?

I did multiple ways(Redistributing from EIGRP to OSPF , Creating a dummy default route, Added default-information originate always). It was showing the metric of 1 in those scenarios!

[MHM Cisco World]

I run lab

in R1 if default route from static or from bgp in R3 the metric is 1

for your case can I see cisco doc. talking about 20 ?

[MHM Cisco World]

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13692-21.html

MHM

[Paheeradan Nagulan]

@MHM Cisco World ,

Yes, I see Cisco have mentioned default metric =1 and the  default metric type = 2 in your link. Not sure why they have mentioned differently in the other document. Anyways thank you clearing up my doubt. 

[Paheeradan Nagulan]

Hi @MHM Cisco World ,

First of all, thank you for taking your time to spin up a lab to test it. Yes, I did see the same behavior(The metric of 1).

Here is the doc that is talking about the metric of 20. May be Cisco is having some inconsistency about this.

https://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8606-redist.html

Specifically here is the line I was referring to in that doc.

"Note: If a metric is not specified, OSPF puts a default value of 20 when it redistributes routes from all protocols except Border Gateway Protocol (BGP) routes, which gets a metric of 1."

[MHM Cisco World]

Get it let me check one point 

MHM

[MHM Cisco World · Accepted solution]

friend he talking about redistribute prefix and the default metric ospf add into these prefix 
it not talk about default route 
default route always use 1

where other prefix when redistrubte into ospf it may have
1 if it from BGP
20 if it from static or other IGP

[Paheeradan Nagulan]

Hi @MHM Cisco World ,

Ah, didn't think about redistributing the specific prefixes. I need more coffee lol  . Yes, you are right. It makes perfect sense now. Thanks for the explanation!

[paul driver]

Hello
@Flavio Miranda @MHM Cisco World  I would say its irrelevant how the default is originated for an default opsf route to be advertised into opsf then my understanding its mainly performed with the default-information originate command (excluding using network 0.0.0.0) appended into the opsf process. but with a default metric-type of E2 or a metric-type of E1 UNLESS it also with own seed metric appended to either.

[paul driver]

Hello
Added default-information originate always). It was showing the metric of 1 in those scenarios! 

What you see is correct - if you think about it - its being injected locally by the rtr so the metric will be 1 by default metric-type 2 if you set it to type-1 it will increase due to link cost being added - 

additionally if you add you own seed metric to the originate that will become the default value