I'll sort of want shock capture again on the surreal link
in the output we can see a hollow packet sent by writer 1.
So this is an no SPF packet sent to the multicast address for 0 SPF.
We can see that it showing as a unit cost packet in each GLC.
The protocol type is IP version for we can see the source IP address destination ip address shown here
once again the protocol type is 0 SPF.
So it's protocol 89 and the protocol used is always P.F. and we can see that it's a hollow packet with
this network mask and it's from this Rhonda
so looking at the HDD see messages.
Notice it's IP version 4 as the protocol here is CTP.
Different type.
Here is slop.
A different type.
And once again if we ping using IP version 6 his IP version 6 a different HDL type what I'll do now
is purposely change the encapsulation on one side to something else.
So the different encapsulation is but I'll set it to BP and what we should notice is that the interface
goes down.
We can see that oh SPF is saying that the relationship has gone down and that the line protocol has
gone down.
So show interface serial to slash zero
in the output we can see that the physical interfaces up but the line protocol is down encapsulation
is BPP.
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 of SPF has gone down show interface serial to 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 PDP.
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 keep the 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 keep lives can traverse the link to ensure that things are working properly
so the line protocol is up 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 the side we can see that the interface came up with peer relationships
were formed and if we look at the interface
we can see that the interfaces up encapsulation as HTC noticed that keep alive you know why shock capture
scrolling up can see a lot of negotiation taking place between 0 SPF neighbors
what I'd like to point out here is notice that keep lives so there is a keep alive scent from one side
to the other.
And notice we have sequence numbers for the keeper lives so there is 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 1 as the interface came up again
here's the 0 SPF negotiation here's the IP version 6 and negotiation and notice share all the keeper
lives continuing bunch of 0 SPF stuff.
Notice the sequence numbers in the keeper lives because the interface came up again on Robert 2.
So those keep the lives as 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.