In this video, I'm going to discuss routed ports on Ethernet switches in this gns3 topology
I have two IOS V layer 2 switches and an IOS V router.
The devices have no configuration.
So they've just booted up and I'll bypass the initial configuration dialog on the router
and let's start by configuring hostnames on the switches
and I'll configure a hostname on the router. So no configuration has been done on these devices at all.
They're using the default configuration and I've simply changed the hostname.
So show CDP neighbors on switch 1 shows me that switch 2 is available on the gigabit 00 interface
CDP was advertising switch 2 with the name switch until I changed it. On switch 2 show CDP neighbor.
We can see switch 1 connected to Gigabit 00.
We don't see the router on gigabit 01 because the routers interfaces are shut down by default, show
interface gigabit 00 switch port.
Here's the command.
We can see that the interface is enabled as a switch port.
It's using dynamic auto DTP mode or dynamic trunking protocol mode the VLAN that the port belongs
to is VLAN 1 because it wasn't able to negotiate trunking with switch 2.
There are no trunk's configured on the switch.
So show interface gigabit switch port, we can see that it's a static access port negotiation of
trunking is enabled but it hasn't negotiated trunking with the other side.
The interface belongs to VLAN 1 on switch 2
we would see something similar.
So show interface gigabit 00 switch port.
The interface is enabled as a switch port using dynamic auto mode.
So when we look at the VLANs at the moment only VLAN 1 and the other default VLANS are configured
on the switches.
We're not going to worry about FTDI and Token Ring in these videos.
What I could do is create a switch virtual interface or SVI you do that by using the interface VLAN
command, we can see that the interface has gone down.
But what I could do is configure an IP address on this interface and then no shut it.
I could then also do something similar create an SVI or switch to a virtual interface for VLAN
1
and give the switch an IP address and no shut the SVI. Interfaces come up on both sides.
So we should be able to ping switch 2 from switch 1 there's the ping again and we should be able
to ping switch 1 from switch 2.
So the physical interface is a layer 2 interface gigabit 00 is enabled as a switch port interface.
It's a layer 2 interface it supports protocols such as spanning tree.
Notice this port is the root port on switch 2 and it's forwarding, show spending tree here shows that
gigabit 00 is the designated port on this switch and it's also forwarding protocols such as DTP and spanning
tree run across switch ports or layer 2 ports
But what I could do as an example on switch 2 is make the port a routed port by using the command no
switch port interfaces come up and now when we type the show interface gigabit 00 switch port
notice we're told that the switch port is disabled. Whereas on this side it's still enabled as a switch
port and we can see the access VLAN that the port belongs to.
We'll also be able to see whether it becomes a trunk
but that's not true on a routed port.
Another difference between a routed port and a switch port is you can configure an IP address directly
on the interface.
Do show run interface gigabit 00.
Notice it's disabled as a switch port and an IP address has been configured directly on the interface.
Whereas if I try that here and try and configure an IP address it's not recognized.
So at this point, I'll just change that IP address to make it consistent
because this is switch 2.
But notice the IP address command is not available on this side because it's currently a switch port.
But if I type no switch port and then IP address notice I can configure the IP address on the interface
do show interface gigabit 00 switch port it is disabled as a switch port.
But I can ping switch 2 through that interface.
So shows spanning tree notice spanning tree is not enabled on gigabit 00 previously gigabit 00 was a
designated port.
But now it's not shown in the output because spanning tree and dynamic trunk protocol do not run on
routed ports.
Gigabit 00 does also not appear on this side, show run interface gigabit 00
shows us that an IP address is configured on the interface.
If I enable this port as a switch port and look at the running config of that interface again.
Notice the IP address has been removed and spanning tree is running on that interface
once again. So interface gigabit00 no switch port IP address 10 122
shows spanning tree, spanning tree is not running on gigabit 00 and I should be able to ping switch 1.
So show IP interface brief shows us that this interface has an IP address configured on it whereas this
interface is a layer 2 interface and the SVI or switch virtual interface is used as the layer
3 interface. So show VLAN brief notice gigabit 00 is not in the list of interfaces that belonged
to VLAN 1, this interface
Gigabit 01 is a layer 2 interface and belongs to VLAN 1 and has this as it's layer 3 IP address.
So basically when you type no switch port you're turning that interface into a routed interface so it
acts like a router.
So gigabit 01 now
is configured as a routed interface and on a router we will do something similar
no shut the interface and configure an IP address directly on the interface and we should be able to
ping switch 2 through that routed interface which we can.
We could also enable a routing protocol.
So I'll enable EIGRP on all interfaces could do the same here router EIGRP 1 and enable EIGRP
on all interfaces. So show IP EIGRP interfaces its enabled in all interfaces and the neighbor relationship
has been established.
Show IP EIGRP neighbor, the neighbor relationship is established on the gigabit 01 interface not on
the SVI but once again if we changed gigabit 00 to a switch port and then enabled EIGRP on this side
notice the difference in the neighbor relationships.
So show IP EIGRP neighbor, no neighbor relationship is established because I need to make this a switch
port to put them back in the same subnet.
So let's check our pings, can router 2 ping router 1 at the moment it can't and that's probably because
of spanning tree.
Notice that port is learning.
So we've got to wait for spanning tree to converge before the EIGRP can form a neighbor relationship.
Routed ports however don't use spanning tree so they will converge quicker than a spanning tree port will.
So the convergence has just taken place.
EIGRP neighbor relationship is established.
So show IP EIGRP
neighbor notice the difference.
This neighbor which is switch 1 has been learnt on VLAN 1 whereas the router has been learnt on the gigabit
01 interface. So show run interface gigabit 00 and 01
notice the difference switch port is enabled on gigabit 00 no switch port has been configured on gigabit
01 when we ping from switch 2 to switch 1
we're using the SVI interface but when we ping from switch 2 to router 1 we're using the physical interface.
So routed ports are typically used between switches and routers for example where a router connects
you to the Internet, switched of virtual interfaces and switch port interfaces are typically used in
a campus environment where you need to tag multiple VLANs across an interface a routed port doesn't
have the concept of VLANs there are no VLANs you don't run spanning tree and you don't run DTP or
dynamic trunk protocol.
The port is a routed port in the same way that you configure a routed port on a router.
So again show IP EIGRP neighbor.
Notice the difference in how the neighbor relationships are formed.
I hope you found this video useful if it's been of benefit to you.
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I wish you all the very best.