I'll start a Wireshark capture again.
On the serial link.
In the output, we can see a hollow packet sent.
By right of one.
So this is an OSPF packet sent to the multicast address for OSPF.
We can see that it's showing as a unicast packet in hdl-c.
The protocol type is IP version four.
We can see the source 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 hello packet with this
network mask.
And it's from this router.
So looking at the.
TLC messages notice its IP version for as the protocol.
Here is CDP.
Different type here is slope.
A different type.
And once again.
If we ping using IP version six.
His IP version six a different hdl-c type.
What I'll do now is purposely change the encapsulation.
On one side to something else.
So the different encapsulation, but I'll set it to pop.
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 two.
Slash zero.
In the output.
We can see that the physical interface is up, but the line protocol is down.
Encapsulation is PPTP.
This means that we don't have a layer one problem.
The interface is physically connected, but this is showing us that we have a layer two problem, which
in our case is a encapsulation issue.
On this side.
OSPF has gone down.
Show interface serial two.
Slash zero.
So there's the command.
The interface is up physically, but the line protocol is down.
The reason why is the encapsulation on the side is hdl-c, but the encapsulation on the side is PPTP.
So for the interface to be up up you need to ensure that the encapsulation on both sides is the same.
So once again on the side, I'll change it to Hdl-c.
And hopefully what should happen is the interface comes up after a while.
Now that's based on keeper lives, so you may have to wait a while.
Keep the lights on these when interfaces 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 an interface and expect it to immediately be working or immediately to go down.
Wait a few seconds so that keeper lives can traverse the link to ensure that things are working properly.
So the line protocol was upped down at that time.
And notice here it went up.
So always wait a few seconds so that keeper lives can succeed from one side to the other.
The encapsulation is now hdl-c.
On this side we can see that the interface came up, OSPF relationships were formed and if you look
at the interface.
We can see that the interfaces up up encapsulation is TLC.
Notice the keep alive.
In a Wireshark capture.
Scrolling up.
You can see a lot of negotiation taking place between OSPF neighbors.
What I'd like to point out here is notice the keeper lives.
So there's a keep alive sent from one side to the other.
And notice we have sequence numbers for the keeper lives.
So there's an outgoing sequence number and a returned sequence number for the keeper lives.
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 one as the interface came up again.
Here's the OSPF negotiation.
He has the IP version six and negotiation and notice here are the keeper lives continuing a bunch of
OSPF stuff and notice the sequence numbers in the keeper lives because the interface came up again on
router two.
So those keeper lives are shown.
So it's important that both sides have the same encapsulation.
It's important that you check the encapsulation.
Check that the physical interface is up.
Check that the line protocol is up.
And wait a few seconds for the keeper lives to succeed on both sides.
So wait, for instance, half a minute to give it time to settle down and to send and receive keeper
lives.