Sub interfaces in router to connect other routers sub interfaces

[Cisconew]

Hi,
I have learned how to create subinterfaces on a router for inter-VLAN routing purposes. Recently, I have noticed that routers can be connected to other routers using subinterfaces. Can somebody explain how to do that? Please find below the network topology with sub interfaces  for reference.

[MHM Cisco World]

I dont test before' but you can if one send tag other can receive and correct match traffic to it subnet.

So I think Yes you can 

[MHM Cisco World]

Friend not only native vlan1 but all vlan you can config it.

interface g1.531

encapsulation dot1Q 1 531

ip address x.x.x.1

!

R2:

!

interface g1.531

encapsulation dot1Q 1 531

ip address x.x.x.2

[Flavio Miranda]

Hi @Cisconew 

  You can do like this

R1:

!

interface FastEthernet0/0.1

encapsulation dot1Q 1 native

ip address 1.1.1.1 255.255.255.252

!

R2:

!

interface FastEthernet0/0.1

encapsulation dot1Q 1 native

ip address 1.1.1.2 255.255.255.252

[DanielP211]

You connect interfaces as you would any other, the only difference is the tagged vlan's. So connect them as normal and create taggs for VID's and a trunk interface (switchport mode trunk)

[Cisconew]

Hi,

I have tried this in Eve-ng.

I have created the 3 sub interfaces for

g 0/1interface of R1,R2 and R3 as (G 0/1.12 , G 0/1.13, G 0/1.23 )

But How to connect 3 routers using those interfaces.

I want to connect this 3 Routers as follows.

R1's G 0/1.12 interface with R2's G 0/1.12 (R1>R2)

R1's G 0/1.13 interface with R3's G 0/1.13 (R1>R3)

R2's G 0/1.23 interface with R3's G 0/1.23 (R2>R3)

The configuration  for 3 routers as:

The sub interfaces are not listed in list of interfaces. 

 Only able to connect routers using physical interfaces.

[MHM Cisco World]

You must assign IP to subinterface in

cli

And 

Last you must no shut the parent interface.

[Flavio Miranda]

You need to think first on the physical interface. If you connected the

Gi0/2 from R1 to G0/2 to R3

between then you can have subinterface by adding the command

inter gi0/2.1

 encap dot1q 1

ip add x.x.x.x x.x.x.x

Do the same on both routers and then R1 and R3 can communicate through subinterface. Use the same logic for the other routers.

But the subinterface will be tyed to the physical interface and will allow communication between those routers only.

[Cisconew]

But I have configured the sub interfaces in each Routers.Then I shutdown the Routers and tried to connect using Physical interfaces.But I couldn't do like below topology where they have used G1 based sub interfaces for almost all the routers.

[Flavio Miranda · Accepted solution]

I believe you are confusing subinterfaces with Interfaces. On the print you shared, Each router connection is one interface. So, look the note I did, A,B,C and D are different interfaces. So, you can not have

G.1.XX surrounding

the router like that.

Gi1/x

is the physical interface. It connect this router to another Router, right? You can only have subinterface with

G1.XX

between those 2 routers.  You can not have

Gi1.XX

connecting multiples Routers.

 Between R2 and R2, the interface is different and you need to change the subinterface accordingly.

[MHM Cisco World]

I think about this' I see this port simple before but I need to be sure from you'

This book talking about

 l2vpn

?

[MHM Cisco World]

531 it cannot  be IP and cannot be port number' there is no router even SW have 531 ports.

So when I see some

l2vpn

video I see same port naming use 

So I think what you see is service instance

l2vpn