|
0:00:14
|
So now, let's take a look at some examples of what's
|
|
0:00:21
|
The topology I'm using here
|
|
0:00:24
|
matches the volume 1
|
|
0:00:27
|
As I mentioned, the PDF is available there for
|
|
0:00:33
|
And we could see, we have the IP
|
|
0:00:40
|
are 155.X.
|
|
0:00:44
|
Then, the number of the routers.
|
|
0:00:47
|
So, in this case, the link between
|
|
0:00:53
|
Whereas the point-to-point link
|
|
0:00:59
|
The X value here is referring
|
|
0:01:05
|
where in the case of today,
|
|
0:01:09
|
So, this would then mean that
|
|
0:01:12
|
is gonna be 155.10.146.4 on router 4,
|
|
0:01:26
|
So again, this topology is based
|
|
0:01:32
|
If you were to load the full Layer 2
|
|
0:01:37
|
then, your topology would
|
|
0:01:42
|
So here, were gonna
|
|
0:01:47
|
with some different
|
|
0:01:50
|
We have the Ethernet interface
|
|
0:01:55
|
we have the point-to-point
|
|
0:02:00
|
Okay, in this case, this point-to-point link
|
|
0:02:06
|
Could likewise run PPP.
|
|
0:02:08
|
That's gonna be the same
|
|
0:02:12
|
then, this frame relay interface,
|
|
0:02:16
|
this is the main serial interface in frame
|
|
0:02:22
|
So, if we were
|
|
0:02:25
|
and we look at the Show IP Interface Brief, we can
|
|
0:02:32
|
If we look at the Show
|
|
0:02:37
|
the frame relay interface here is doing
|
|
0:02:42
|
with the frame relay
|
|
0:02:46
|
So first, let's look at
|
|
0:02:50
|
we're gonna try two different types
|
|
0:02:52
|
Both to the next hop
|
|
0:02:57
|
The device on the
|
|
0:03:01
|
where from the Show
|
|
0:03:03
|
we could see that switch 2 has a
|
|
0:03:09
|
It has this port channel that's going
|
|
0:03:16
|
Then, it has a couple
|
|
0:03:21
|
So first, one router 5,
|
|
0:03:25
|
And we'll out a static route that goes
|
|
0:03:38
|
And those points to the
|
|
0:03:41
|
So, this is via 155.10.58.8.
|
|
0:03:49
|
Now, since we are already directly
|
|
0:03:53
|
this 155.10.58.8, we should have
|
|
0:04:00
|
because they have a route back to my
|
|
0:04:05
|
If we were to look at the
|
|
0:04:11
|
so the actual final destination
|
|
0:04:15
|
The router says that "This is
|
|
0:04:20
|
I know what the next hop value is, but
|
|
0:04:27
|
So, we told the router, where
|
|
0:04:31
|
So, who's the Layer 2 neighbor, but we didn't
|
|
0:04:37
|
So now, this means the router would
|
|
0:04:41
|
It would have to do
|
|
0:04:43
|
So, router 5 says,
|
|
0:04:50
|
This is via Fast Ethernet 0/0.
|
|
0:04:54
|
This address here, then should be
|
|
0:05:00
|
If we look at the Show ARP
|
|
0:05:03
|
for Ethernet, we can see, we know
|
|
0:05:07
|
So, this then means, when I'm sending
|
|
0:05:15
|
In the Layer 2 header, I'm
|
|
0:05:21
|
If we look at the ARP cache
|
|
0:05:26
|
we don't have any MAC address entries for
|
|
0:05:33
|
So, it's my two interfaces.
|
|
0:05:35
|
My two Ethernet interfaces.
|
|
0:05:37
|
Plus the MAC address of switch
|
|
0:05:44
|
Now, if we look at the routing table,
|
|
0:05:48
|
Show IP Route.
|
|
0:05:50
|
We have the static
|
|
0:05:53
|
We could see that the
|
|
0:05:58
|
There's no metric value
|
|
0:06:01
|
So, we have only the distance
|
|
0:06:05
|
And it says, "This is the next hop."
|
|
0:06:10
|
Likewise, the router then does
|
|
0:06:13
|
It says, "I found this connected
|
|
0:06:17
|
So, it means we resolved the Layer 2
|
|
0:06:24
|
Now, if we were
|
|
0:06:30
|
to say, "To get to...
|
|
0:06:35
|
this destination, we're not
|
|
0:06:40
|
We're just pointing
|
|
0:06:47
|
We'll see that it's not actually
|
|
0:06:51
|
So, router 5 will still have
|
|
0:07:00
|
And...
|
|
0:07:03
|
Let's see, that is the correct...
|
|
0:07:08
|
interface. Fast Ethernet 0/0.
|
|
0:07:25
|
Let's now look at router 5
|
|
0:07:31
|
We can see that router 5 is now
|
|
0:07:37
|
If we were to Debug ARP,
|
|
0:07:42
|
we'll see that when we try to send
|
|
0:07:47
|
we need to send a request to figure
|
|
0:07:52
|
In most designs,
|
|
0:07:57
|
We could see 5 is ARPing for the
|
|
0:08:01
|
Because when we look
|
|
0:08:04
|
this address is not actually
|
|
0:08:10
|
It's this address that is on
|
|
0:08:15
|
So, this means router 5
|
|
0:08:18
|
for someone who is
|
|
0:08:21
|
Under normal cases, the devices on
|
|
0:08:28
|
Only if some Layer 3 device on
|
|
0:08:35
|
would they send a response with their own
|
|
0:08:42
|
Now, in most networks, Proxy ARP should be
|
|
0:08:50
|
It can be used for a Layer 3
|
|
0:08:55
|
to figure out what are
|
|
0:08:59
|
So, essentially,
|
|
0:09:01
|
is send ARP request for
|
|
0:09:05
|
Look at what the router replies
|
|
0:09:10
|
It means that the router would have routing
|
|
0:09:16
|
Now, probably what's happening
|
|
0:09:21
|
this version probably is not
|
|
0:09:24
|
So, on switch 2, if I were to look
|
|
0:09:35
|
It says, "Proxy ARP is enabled,
|
|
0:09:38
|
but local Proxy ARP is disabled."
|
|
0:09:41
|
So, this means that for its own
|
|
0:09:49
|
But it would for someone
|
|
0:09:53
|
So, for example,
|
|
0:09:59
|
If we were to go to switch 4,
|
|
0:10:02
|
and I'm gonna configure
|
|
0:10:07
|
that points towards this segment.
|
|
0:10:10
|
So, I'll say, to get to this VLAN 58, I'm gonna
|
|
0:10:15
|
Switch 2's port channel interface.
|
|
0:10:24
|
So, on switch 4, we'll say,
|
|
0:10:26
|
to get to 155.10.58.0/24
|
|
0:10:34
|
I'm going to 155.10.108.8.
|
|
0:10:41
|
If I try to reach someone
|
|
0:10:44
|
assuming they have
|
|
0:10:47
|
I should be able
|
|
0:11:12
|
So, let's see...This switch 4...
|
|
0:11:16
|
Oh, actually, you
|
|
0:11:18
|
Let's see, the IP
|
|
0:11:20
|
Okay, so, for the switches,
|
|
0:11:22
|
we talked about this last week.
|
|
0:11:24
|
By default, routing is off.
|
|
0:11:28
|
So, actually, this is probably
|
|
0:11:30
|
It's not ARPing because it can't
|
|
0:11:35
|
So, if we try again on...
|
|
0:11:39
|
router 5, we could see now,
|
|
0:11:42
|
So, if we ping the final destination,
|
|
0:11:50
|
5 sent an ARP request
|
|
0:11:53
|
about the VLAN 8 interface.
|
|
0:11:56
|
It says, "It receives the response
|
|
0:12:00
|
Now, if we look at the ARP cache,
|
|
0:12:06
|
notice that we have that same
|
|
0:12:12
|
This is the MAC address that's
|
|
0:12:18
|
interface of switch 4.
|
|
0:12:21
|
Or excuse me, switch 2.
|
|
0:12:25
|
So, we essentially have redundant
|
|
0:12:30
|
The place where this
|
|
0:12:35
|
is that when we need to ARP
|
|
0:12:39
|
it means that the ARP cache
|
|
0:12:44
|
And where this happens is that
|
|
0:12:49
|
that points to the
|
|
0:12:54
|
So, let's now say
|
|
0:12:58
|
as opposed to saying,
|
|
0:13:06
|
I'm gonna remove this
|
|
0:13:09
|
default route."
|
|
0:13:11
|
So, we'll say now, "Just for any destination
|
|
0:13:16
|
I'm gonna go to Fast Ethernet 0/0."
|
|
0:13:21
|
This should then mean that
|
|
0:13:28
|
It should be able to reach
|
|
0:13:30
|
It should be able to reach
|
|
0:13:33
|
And then, basically, that's it because switch 2
|
|
0:13:40
|
But if we were to ping those
|
|
0:13:44
|
let's say, we ping 155.10.8.8,
|
|
0:13:52
|
we ping 150.10.8.8, which
|
|
0:14:00
|
If we ping the port channel
|
|
0:14:07
|
on switch 2 and on switch 4.
|
|
0:14:09
|
Note that for every packet
|
|
0:14:13
|
we're sending this ARP request, and then,
|
|
0:14:19
|
So, if we Show ARP,
|
|
0:14:22
|
we see that for all
|
|
0:14:26
|
we have to have a Layer 2 to
|
|
0:14:31
|
Now, if router 5 were
|
|
0:14:34
|
that is routing packets
|
|
0:14:37
|
it means that for every
|
|
0:14:41
|
no matter what destination
|
|
0:14:43
|
If they're going to the address of Google's
|
|
0:14:48
|
it means that router 5 would have to send
|
|
0:14:55
|
If the device on the end of
|
|
0:15:00
|
The connectivity is gonna go through, but it means
|
|
0:15:07
|
So, if our end hosts are sending packets
|
|
0:15:13
|
then, it means we'd have
|
|
0:15:19
|
So, if we look at
|
|
0:15:23
|
Addresses that are actually
|
|
0:15:31
|
108.1, 108.2...
|
|
0:15:36
|
108.3, etc....
|
|
0:15:39
|
If we look at the ARP cache,
|
|
0:15:42
|
we now have entries
|
|
0:15:47
|
The reason being that
|
|
0:15:51
|
it knows what the
|
|
0:15:55
|
that for any destination,
|
|
0:15:58
|
I'm going to the Ethernet.
|
|
0:16:02
|
But it doesn't already know who
|
|
0:16:08
|
So, it figures that whatever the destination is,
|
|
0:16:12
|
Because that's what our route is saying,
|
|
0:16:17
|
Where in reality, it should be towards
|
|
0:16:26
|
Now, if we were to do this
|
|
0:16:30
|
let's say that we remove the...
|
|
0:16:31
|
the default route on...
|
|
0:16:35
|
router 5 towards the Ethernet.
|
|
0:16:37
|
And I'm gonna point it towards
|
|
0:16:46
|
So on router 5, let's say,
|
|
0:16:52
|
And I'll remove...
|
|
0:16:56
|
the static entry.
|
|
0:16:58
|
We're gonna replace this with a route
|
|
0:17:07
|
If we look at the Debug IP Packet,
|
|
0:17:22
|
and let's say now,
|
|
0:17:24
|
some of the addresses that
|
|
0:17:28
|
So, each of these routers has a
|
|
0:17:34
|
150.10.3.3. on router 3.
|
|
0:17:39
|
150.10.2.2. on router 2 etc.
|
|
0:17:42
|
So, router 5 has
|
|
0:17:46
|
Since these neighbors should already be able to
|
|
0:17:51
|
because they're all
|
|
0:17:53
|
it means that ideally, router 5 should
|
|
0:18:00
|
But if 5 now sends a packet
|
|
0:18:05
|
it says, "The routing process
|
|
0:18:13
|
We'll see that in the Debug IP Packet,
|
|
0:18:17
|
And let me turn off
|
|
0:18:21
|
No Service...
|
|
0:18:25
|
No Service Time Stamps.
|
|
0:18:34
|
Then, we'll do this ping again.
|
|
0:18:34
|
We should see that
|
|
0:18:39
|
the routing process
|
|
0:18:42
|
We can see this because
|
|
0:18:48
|
routed the packet via the RIB."
|
|
0:18:50
|
The RIB is the Routing Information
|
|
0:18:56
|
This is telling us that this destination
|
|
0:19:03
|
Why would this packet be
|
|
0:19:07
|
Because it's locally generated.
|
|
0:19:09
|
So again, any locally generated,
|
|
0:19:12
|
so, locally originated
|
|
0:19:15
|
So, anything coming from or going to the router,
|
|
0:19:21
|
It's only the transit traffic
|
|
0:19:25
|
So, when we're looking at the debug here, Debug
|
|
0:19:28
|
we can see the Layer 3 debug
|
|
0:19:34
|
because this is
|
|
0:19:36
|
So, this first line says that
|
|
0:19:40
|
The routing process had an entry, and it
|
|
0:19:44
|
Now, we go on to
|
|
0:19:49
|
Actually, this middle one,
|
|
0:19:52
|
So, it's the 3-step process: routing,
|
|
0:19:57
|
We get to the Layer 2 encapsulation.
|
|
0:19:59
|
It says, "This is failing,
|
|
0:20:02
|
because there is no map entry
|
|
0:20:10
|
So, what is this talking about here?
|
|
0:20:15
|
We see that both in the Layer 2
|
|
0:20:17
|
and the Layer 3 debug,
|
|
0:20:22
|
This means that
|
|
0:20:25
|
the router did not know
|
|
0:20:30
|
most likely because it doesn't know the Layer 2
|
|
0:20:37
|
So, this means...
|
|
0:20:39
|
when we look at router 5's result
|
|
0:20:41
|
in the routing table,
|
|
0:20:44
|
and in the frame
|
|
0:20:48
|
5 would only be able to reach destinations that
|
|
0:20:57
|
And design-wise, it doesn't
|
|
0:21:01
|
Just basically a misconfiguration.
|
|
0:21:02
|
Okay, we can get it to work with
|
|
0:21:08
|
but there's no reason in the
|
|
0:21:11
|
What I would actually have to do...
|
|
0:21:13
|
is that on the serial link,
|
|
0:21:17
|
for whatever destination
|
|
0:21:20
|
I'd have to put a static
|
|
0:21:24
|
So, I would say that router 1's loopback
|
|
0:21:30
|
That router 2's loopback
|
|
0:21:34
|
3's loopback is towards router 3 etc.
|
|
0:21:39
|
But as you can imagine, it doesn't make
|
|
0:21:43
|
for every possible destination.
|
|
0:21:48
|
So again, if this were
|
|
0:21:50
|
that you're using frame
|
|
0:21:52
|
or you're using it to reach other
|
|
0:21:58
|
then, you would need frame
|
|
0:22:02
|
We should see now, router 5 would be
|
|
0:22:16
|
but it wouldn't be able
|
|
0:22:22
|
because we don't know
|
|
0:22:25
|
for that particular destination.
|
|
0:22:30
|
So, in reality, for
|
|
0:22:33
|
it doesn't make sense
|
|
0:22:37
|
default route towards
|
|
0:22:41
|
Regardless of whether it's
|
|
0:22:45
|
any multipoint link,
|
|
0:22:47
|
we should not have a
|
|
0:22:51
|
If this were a point-to-point interface,
|
|
0:22:53
|
then, it would be a different story.
|
|
0:22:56
|
So, if I took this out,
|
|
0:23:02
|
and let's say we point it at the point-to-point
|
|
0:23:09
|
so, if we look at this interface as 0/1/0,
|
|
0:23:12
|
this is an HTLC interface
|
|
0:23:18
|
If I were to now ping
|
|
0:23:21
|
the LAN interface of router 4,
|
|
0:23:29
|
or the...
|
|
0:23:32
|
the loopback of router 4, 150.10.4.4.
|
|
0:23:38
|
Router 4 also has that...
|
|
0:23:41
|
link that goes to one of the
|
|
0:23:45
|
So, if I were to ping 204.12.10.4,
|
|
0:23:52
|
we could see, router 5 has
|
|
0:23:55
|
because from a Layer 2 point of view,
|
|
0:23:58
|
it doesn't care what
|
|
0:24:02
|
because there's only one possible
|
|
0:24:07
|
It says that, "This link, serial 0/1/0,
|
|
0:24:10
|
it's point-to-point, there's only one
|
|
0:24:14
|
So, I don't even need a Layer 2 address from
|
|
0:24:20
|
Once the router
|
|
0:24:22
|
we just take out HTLC header
|
|
0:24:25
|
put it on top of the Layer 3 frame, and then
|
|
0:24:33
|
But when we look at the
|
|
0:24:37
|
since there are multiple
|
|
0:24:41
|
this is why we need that resolution.
|
|
0:24:44
|
Either with the frame relay maps,
|
|
0:24:46
|
with the inverse ARP,
|
|
0:24:48
|
or the ARP process for the IPv4.
|
|
0:24:52
|
We'll see on IPv6, we have the equivalent of
|
|
0:24:57
|
or ICMP ND process.
|
|
0:25:00
|
That's the equivalent of ARP for IPv6.
|
|
0:25:04
|
So again, this is both for regular
|
|
0:25:10
|
If we point the route to the next hop,
|
|
0:25:13
|
it means we would use the Layer 2 address
|
|
0:25:19
|
But if we point it at
|
|
0:25:22
|
the Layer 2 resolution is for the final destination,
|
|
0:25:29
|
With the point-to-point interface, it doesn't matter,
|