[AUDIO LOGO]
Next up, we're moving on to Trouble Ticket 4.
To this ticket, we're still going to be on MPLS Topology 1.
However, notice that this time our core protocol
has switched to OSPF.
Our ticket, however, may look just a little bit familiar.
Here we have Router 6 is not doing
label switching to 10.5.5.5.
So once again, we're back to looking at Router 6.
Going to Router 5's loopback, we've seen this before.
But of course, it's a different issue this time,
and we have a different core protocol this time.
So as per usual, let's jump in, verify the ticket,
make sure that it's actually broken,
and then of course, we'll start our troubleshooting process.
So we'll start with our trace.
Again to Router 5's loopback, sourcing it from our loopback.
So as we can see here on the trace, the ticket is correct.
We are not doing label switching.
So let's again go to our first hop router, Router 1,
and see if it has any information about Router 5.
So on Router 1, let's do a show OSPF database opaque-area
for extended prefixes, and let's just
include the 10.5.5.5 since we know what we're looking for.
What we see here is we have no entry.
Now in this particular case, if you've never
done this command before, maybe you're not confident
that the filter worked.
So let's try it for something else
that we suspect is probably working.
Let's try for example, Router 3's loopback,
and we see here we have an entry for it.
So that is in our database.
So the fact that Router 5 is not is a pretty good indicator
that we have a problem.
Let's go over and see if Router 3 has a label for Router 5.
So we'll simply do the exact same command on router.
We can see it doesn't have an entry either.
Let's see if it has an adjacency SID for it.
So let's do "show OSPF segment routing adjacency-sids,"
and we see here that we actually do have an adjacency SID 24,008
for neighbor 10.5.5.5 out our Gigabit 0/0/0/0 interface,
which looks correct.
So let's verify the OSPF neighborship.
We'll do a show OSPF neighbor detail.
So we see here we're looking at Neighbor 5.
We see that the state is full.
And again, we see down here that the adjacency SIDs are being
exchanged, which we just saw.
But overall, this neighborship looks
perfectly fine from Router 3's perspective.
So let's go ahead and jump over to Router 5,
see if we configure what's going on over there.
So let's do a show IP OSPF database opaque-area
type extended prefix self-originated.
We'll look at the database entries
that Router 5 itself is creating.
This is just a way of filtering the output
to make it a little more relevant.
And we see here that Router 5 is not generating anything.
Well, does it have any entries?
Let's take the self-originated off,
and we see that we are, in fact, getting entries type-10 Opaque
LSAs from other devices.
Just as an example, here's advertising Router 1 telling us
about its prefix SID.
So we are getting the information.
We're just not generating any.
So let's see if Router 5 is even configured
to generate a prefix SID.
Let's just do show run, and we'll
look for the section segment.
So what we see here is under segment-routing MPLS
in the global config, it actually
is configured to generate a prefix SID for its loopback.
It's configured to generate 16,005.
But we can see that it's not doing that.
So since it's set to generate an absolute value of 16,005.
Let's make sure that's within our SRGB.
So let's do a show MPLS label range,
and we see that the SRGB is, in fact, set to 16,000/23,999.
So this is the default SRGB range.
Our absolute value is within that range.
So that's not the problem.
So maybe this is an OSPF issue.
Let's do a show run section OSPF.
Now all of these top entries are the OSPF entries
under the interfaces.
So if we look down here at the global process,
we see that all it's configured for is the router ID.
This is not enabled for segment routing.
Now of course, what's interesting about this,
and we saw this in some previous tickets with ISIS
as well, not having the protocol enabled
doesn't necessarily stop the protocol from learning
information.
So this device has learned things like prefix SIDs
from other routers.
It's just not putting its own information into OSPF.
So this is clearly--
probably, our issue.
Let's go ahead and fix this and see if it solves the problem.
So let's go into configuration mode in the Router OSPF 1,
and we'll turn on segment routing for MPLS.
Let's exit configuration.
And let's do our verification.
First, let's do our "show ip OSPF database opaque-area
type extended prefix self-originated," heck
of a command.
And we see here that we are now generating
the type-10 Opaque LSA, Opaque type-7 for the extended prefix.
We see that it is for our loopback interface,
and it's advertising an index SID 5.
So this looks like it's correct.
Let's work our way backwards again,
make sure everything's OK.
If we go back to router and see if it has the extended prefix,
we see that now it does have an entry for the 10.5.5.5/32.
Let's check Router 1, Router 1 also
has that entry for Router 5 now.
So let's go back and verify our original ticket.
So back on Router 6, we'll do our trace again.
So here we see that it is working now.
Of course, our focus being Hop 2,
we see not only are we doing our multi-pathing,
but we're using our Label 16,005,
which was the original ticket.
We were, of course, not doing segment routing/MPLS label
switching.
So I would consider this to be ticket-4 fixed.
So in this ticket, we saw an example of a router that
was running OSPF that had segment routing
enabled globally but did not have it
enabled under the OSPF process.
The interesting behavior, of course, that we see
is that OSPF was still receiving the information.
Router 5 still had information about its peers
and other devices prefixed SIDs.
It just wasn't putting its own prefix into OSPF,
even though it was configured to generate one
under the global configuration.
Once we fixed that, it started putting its prefix SID
into OSPF.
Everybody else then learned it, and of course, everybody else
started using it, and that solved the problem.
I hope this has been informative for you,
and I'd like to thank you for viewing.