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PC1-VLAN1======Switch : Successful pings from the switch
PC1-VLAN2======Switch : *Unsuccessful* pings from the switch

I've got a single switch with a static IP directly connected to PC1 with a static IP, both on the same 192.168.1.0/24 network. The switch has no VLAN's on it except the default VLAN1.

With this setup, the switch can successfully ping PC1.

If I Create a VLAN2 and assign PC1's port to VLAN2, the switch can no longer ping PC1. I would understand if another PC on a different VLAN couldn't ping PC1, but I would think that the switch could ping either.

What am I missing?

Thanks!

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1 Answer 1

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That's the whole point of VLANs. VLANs create a layer-2 separation. You can't get from one layer-2 domain to another without a layer-3 device (router) connecting them. The switch is just another host on a different VLAN.

The VLANs are like yards separated by fences. You need a gate (router) to get from one to the other.

If you add a VLAN 2 SVI on the switch with an address in the same subnet as the PC, you could ping the PC.

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  • Thanks Ron. I understand what you're saying, at least in regards from one attached device to another. However, it would seem to me that the switch itself could ping any device that is attached to it since, after all, it is the 'gatekeeper' of all it's VLAN's. Isn't the switch itself essentially a 'trunk'? It knows about all the devices that are attached to it, regardless of which VLAN, so it seems to me that it should at least be able to ping any of those attached devices.
    – JonDoeCA
    Commented Aug 28, 2015 at 2:02
  • Thanks for the edit. I had to look up SVI so it seems I need to learn a bit more about the core of VLAN's to maybe better understand what's happening.
    – JonDoeCA
    Commented Aug 28, 2015 at 2:07
  • The switch SVI is just another host assigned to a VLAN. It will need a layer-3 device to get to another VLAN. Most Cisco switches will let you set up multiple SVIs so you could have one in each VLAN if you want, but those interface are in VLANs just like connected PCs. If you have something that bridges VLANs together, you can quickly run into spanning-tree problems and get loops that create broadcast storms.
    – Ron Maupin ♦
    Commented Aug 28, 2015 at 2:07
  • Even if the switch had one SVI in VLAN 1, and another in VLAN 2, those SVIs can't communicate without a layer-3 device.
    – Ron Maupin ♦
    Commented Aug 28, 2015 at 2:09

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