Vlan svi routing

[zemerdon]

Good morning,

Just after some clarification please as im new to implementing VLAN and inter-vlan communication.

Sw1 vlan10,20

Sw2 vlan10

Sw3 vlan10,20

Trunks connect to sw2.  My question is do i need an svi on sw2 for vlan20 please (i assume yes)?

Cameras are on vlan10, management is vlan20.

[NetworkNewbie37]

Hello Zemerdon,

I could be mistaken, but from what I understand SVI's are often used in Layer 3 switches.

I'm unsure if that's how you're attempting to setup this topology, however, for a switch to be able to communicate with a VLAN, in this case VLAN 20, that VLAN would need to be created on Sw2 in this example. It would also need some form of routing capability as well which you did seem to mention. Whether this is a RoaS setup, or an SVI on a L3 switch.

There are more experienced people on this matter who can provide further insight, but hopefully this provides an answer.

[zemerdon]

Yeah im using layer3 switches.  Sounds like i need all vlans and all svi creates on all switches that i want to communicate with each other, regardless if they reside on a certain switch or not?

[Joseph W. Doherty]

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@zemerdon wrote:

Trunks connect to sw2.  My question is do i need an svi on sw2 for vlan20 please (i assume yes)?

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(Assuming all 3 switches are L3 switches.)

No, you do not need a SVI on SW2 for VLAN 20, but you could have one there, or any or all of the 3 switches.

SW2 needs to have VLAN 20 known to it, but that's not the same as requiring it to have a SVI for the VLAN.

[zemerdon]

So i could just add vlan20 to sw2 then it is known and not worry about the svi on sw2, since vlan20 is coming from trunks.

I thought maybe an svi was needed on sw2 so v20 could see v10 regardless.

[Joseph W. Doherty]

A L3 interface, such as a SVI, is needed to get traffic between VLANs.

[Jens Albrecht]

Hello @zemerdon,

a switch does NOT need a SVI if it should simply transport client traffic in a Vlan from one device connected via access or trunk link to another device connected with trunk or access link. This kind of transport servcie is Layer 2 only aka switching so a SVI is not needed.

You have to configure a SVI on a switch if you either

• want to send traffice from or to this switch in that Vlan (typically the Management Vlan) or
• the switch is used as a gateway for the clients in that Vlan and routes the traffic to other Vlans.

So whenever the switch offers some kind of Layer 3 service to clients (typically routing) or is the source/destination of that traffic you have to configure a SVI.

HTH!

[balaji.bandi]

Trunks connect to sw2.  My question is do i need an svi on sw2 for vlan20 please (i assume yes)?

yes if you like to manage that switch from remote, you need management VLAN to connect to SW2, as per the information provided.

[arunkumarravi-mv · Accepted solution]

You’ve got three switches in your setup — SW1, SW2, and SW3 — and VLANs 10 and 20 are being used across them. SW2 only has VLAN 10 configured locally, but it’s connected via trunk links to other switches that carry both VLAN 10 and VLAN 20. Now, if SW2 is just passing VLAN 20 traffic through its trunk ports (like a bridge), then it doesn’t need an SVI for VLAN 20. But if you want SW2 to actually communicate with devices in VLAN 20 — like managing them, pinging them, or acting as a gateway — then yes, you do need to configure an SVI for VLAN 20 on SW2. In your case, since VLAN 20 is used for management and you might want SW2 to be part of that management network, it’s a good idea to add the SVI. Just make sure the VLAN is allowed on the trunk ports and the SVI interface is not shut down. This will ensure smooth inter-VLAN communication and proper device management.

[Joseph W. Doherty]

yes, you do need to configure an SVI for VLAN 20 on SW2.

Again (and assuming all switches are L3), SVI doesn't have to be on SW2.  It could be on any of the switches or on all of them.

What switch or switches should have a SVI is "it depends".

[zemerdon]

Thank you sir, that has pretty much cleared everything up in one post.

I appreciate you're time in answering me with simple straightforward information.

I would also like to thank everyone else who has taken their time to reply which builds an understanding for my problem.  Wonderful community, happy travels all.