vlans on layer 3 switch

[carl_townshend]

Hi all, If have 2 vlans on my switch with ip addresses so my clients use the ip as there gateway and i want this going to my router, I put a port in layer 3 mode on the same subnet as my router, would the vlans see the layer 2 port as being directly connected and so can see the rest of the lan ?

[ankurbhasin]

Hi Carl,

There will be a problem in your configuration and the problem is as you have already configured a layer 3 vlan (SVI) on your switch and assigned an ip address and now if you create another layer 3 port and try assigning a same subnet on layer 3 port you will get an overlapping error message as you cannot have 2 layer 3 interfaces with same subnet on same device.

So what you can do is instaed of creating a layer 3 port , configure layer 2 port and assign it to any VLAN for which you have created layer 3 interface and connect your router and all your clinets in any vlan will be able to reach router throug intervlan routing.

HTH, if yes please rate the post.

Ankur

[carl_townshend]

Hi Ankur, the subnets on my vlans will be say 172.30.1.1 /24 whereas the layer 3 port will be on a 172.30/16 address, will this be ok ?, If I do it the way you said I presume I will need to put the router on the same ip range as one as the vlans and put a route on the switch pointing traffic to the router ?

[ankurbhasin]

Hi Carl,

If you do the way I said you just need to put the router on same ip range as on one of the layer 3 interface which you might have configured for any vlan and need not specify any route on switch because it will be directly connected via that vlan and it will be most easy and recommended setup.

Regards,

Ankur

[carl_townshend]

Hi Ankur, but surely this way my normal lan clients will not be able to see the other vlan unless the router has a route pointing to the ip of vlan ?

[ankurbhasin]

Hi Carl,

Does your switch is not a layer 3 switch? If yes then intervlan routing will be done on layer 3 switch.

If it is a layer 2 switch then you need to have intervlan routing on router creating subinterfaces and encapsulation so that all vlans can see each other and you need to have trunk on switchport connecting to the router.

I was presuming that your switch is a layer 3 switch as you told you will be configuring layer 3 port on your switch.

HTH, if yes please rate all post.

Ankur