Layer 2 switch SVI vs Layer 3 switch SVI

[Mohamed Fyaz]

Hello all,

While i was practicing inter vlan routing, i found that cisco 2960 switch has the option to create SVI, but there is no way to enable ip routing.

Since there is no way for us to establish routing between different VLANs on a layer 2 switch, why is there an option for us to create SVI in layer 2 switch?

I understand layer 2 is only to create VLANs and assign the ports to the respective VLANS. 

Correct me if I am wrong and explain me if I am missing out on anything.

Thank You.

Regards,
Fyaz

[Deepak Kumar]

Hi, 

Q: Since there is no way for us to establish routing between different VLANs on a layer 2 switch, why is there an option for us to create SVI in layer 2 switch?

Ans: this is for the management of Switch. 

Regards,

Deepak Kumar

[Mohamed Fyaz]

Hi Deepak,

thanks for the clarification ! :)

[Julio E. Moisa]

Hi,

The SVI on layer 2 switches like 2960 are used for management and testing. 

Every switch must (no mandatory but highly recommended) a management IP address so that is the reason to create a SVI and it will be associated to the ip default-gateway command used to reach the device remotely. The SVI can also be used for other task like source for SSH, NTP, Logging, etc. 

The SVI can also be used for testing in order to make ping to gateway or other IP addresses with source the VLAN (simulating a PC)

Hope it is useful

:-)

[Mohamed Fyaz]

Hi Julio,

Understood! :) I created a dhcp pool in the layer 2 switch. Also created a SVI, giving it an ip address. Later found that it has been assigned as the dhcp server's address.

So in such cases, how are we going to define the management ip.

Please advise.

Thanks,
Fyaz

[Julio E. Moisa]

Hi,

You are welcome :-) 

What will be the management VLAN is up to you, you can choose a VLAN and network for that role only. 

Basically the switches into the same location should use the same VLAN for managemente, so for example, we have 2 switches connected between them and the Management VLAN is 100 with associated network 172.16.100.0/24

SW1 (f1/0/24)  ----- Trunk  ----- (f1/0/24) SW2

SW1

vlan 100

name MGNT

interface vlan 100

name MGNT

ip address 172.16.100.2 255.255.255.0

no shutdown

interface f1/0/24

switchport

switchport mode trunk

no shutdown

ip default-gateway 172.16.100.1   (note, it is the default gateway of the scope for network 172.16.100.0/24)

SW2

vlan 100

name MGNT

interface vlan 100

name MGNT

ip address 172.16.100.3 255.255.255.0

no shutdown

interface f1/0/24

switchport

switchport mode trunk

no shutdown

ip default-gateway 172.16.100.1   (note, it is the default gateway of the scope for network 172.16.100.0/24)

A trunk interface with basic configuration will transport all the VLANs by default. 

Hope it is useful

:-)

[Mohamed Fyaz]

Hi Julio,

Great! this clears my query! :)

Thanks,
Fyaz

[Julio E. Moisa]

Hi

Im happy to see that. 

Have a great day

:-)