All sort of one shot capture again on the serial link
in the output we can see a halo packet.
S. by Rotto 1.
So this is a no SPF packet sent to the multicast address for OSPF we can see that it's showing as a
unicast pocket in HGL see the protocol type is IP version for we can see the IP address destination
IP address shown here once again the protocol type is OSPF So it's protocol 89 and the protocol used
is OSPF and we can see that it's a hollow packet with US network mask and it's from the router.
So looking at the HDFC messages notice it's IP version 4.
As the protocol here is CGP different type here is slop a different type.
And once again if we ping using IP version 6 his IP version 6 8 different HLC type what I'll do now
is purposely change the encapsulation on one side to something else.
So the different encapsulations But I'll set it to.
And what we should notice is that the interface goes down we can see that OSPF is saying that the relationship
has gone down and that the line protocol has gone down.
So show interface serial to slash is zero.
In the output we can see that the physical interface is up but the line protocol is down and kept solution
is GPP.
This means that we don't have a layer 1 problem.
The interface is physically connected but this is showing us that we have a layer 2 problem which in
our case is a encapsulation issue.
On the side OSPF has gone down.
Show interface Ciril to slash zero
surveys the command the interfaces up physically but the line protocol is down.
The reason why is the encapsulation on the site is a deal see putting kept solution on the side is Peepy
So for the interface to be up up you need to ensure that thing kept isolation on both sides is the same.
So once again on the side all change at to HDL see and hopefully what should happen is the interface
comes up after a while.
Now that's based on keep alive.
So you may have to wait a while keep alive on these whining faces are set to 10 seconds.
So it can take a few seconds for the link to either go down or to come up.
Don't know shut to an interface and expect it to immediately be working or immediately to go down.
Wait a few seconds so that keepalive can traverse the link to ensure that things are working properly.
So the line protocol was up or down at that time.
I noticed here it went up so always wait a few seconds so that keep alive can succeed from one side
to the other encapsulation is now a deal see on the side we can see that the interface came up always.
Relationships were formed and if you look at the interface
we can see that interfaces are pop.
You kept isolation is HTL see.
Notice the keepalive you know wash or capture scrolling up the can see a lot of negotiation taking place
between OSPF neighbors.
What I'd like to point out here is notice the keepalive.
So there's a keepalive saint from one side to the other.
I notice we have sequenced numbers for the keep alive.
So there's an outgoing sequence number and a returned sequence number for the keep alive from one side
of the link to the other and what you'll notice is that will keep on being sent here notice the sequence
number was set to 1 as the interface came up again.
Here's the OSPF negotiation.
Yes the IP version 6 in negotiation and notice here are the keep alive continuing bunch of OSPF stuff.
And notice the sequence numbers in the keep alive.
Because the interface came up again on Rodda too.
So those keep alive those shown.
So it's important that both sides have the same encapsulation.
It's important that you check in kept isolation check that the physical interface is up check that the
line protocol is up and wait a few seconds for the keepalive to succeed on both sides.
So wait for instance half a minute to give it time to settle down and to send and receive keep alive.