Identical VLAN gateway config on multiple L3 switches

[PS]

I'm trying to fix a mess that I partly inherited and then exacerbated through ignorance.

We have three X450e-48p switches on a single, flat, /24 network, one per building. One of the switches has a small port-based VLAN but essentially everything else is on the Default VLAN so we may as well have been using L2 switches all this time. Anyway, I need to get this thing under control, so:

The default gateway for basically everything in this 10.10.10.1/24 network is the firewall's ip address. The three switches have ip addresses of 10.10.10.150, 10.10.10.151, 10.10.10.152 which are used to manage them.

Can I create an identical VLAN on each switch such that the default gateway for that VLAN is the same IP address no matter which switch the host is plugged into?

Like, on all three switches can I blow away the VLAN configuration and do this:

create vlan voice_vlan
configure vlan voice_vlan tag 11
configure vlan voice_vlan ipaddress 10.10.11.1/24
configure vlan voice_vlan add ports 1-48 tagged
enable ipforwarding voice_vlan

configure vlan default ipaddress 10.10.10.1/24
configure vlan default add ports 1-48 untagged
enable ipforwarding default

I assume this would create a problem with management access so, given we don't have any dedicated management network to speak of, how would I then manage the switches?

[Jen0342]

this will fail, as the router ( 10.10.10.1) wont know where to send the return traffic bound for the 11 networks... you would want to change it to be building 1 as 10.10.11.1, building 2 is 10.10.12.1, building N is 10.10.1N.1/24... the router at 10.10.10.1 would have to "Know" about the 11,12,13,1N networks so there would be a route that was 10.10.11.x/24 is at 10.10.10.150, 10.10.12.x/24 is at 10.10.10.151 etc.

each switch still needs it 10.10.10.x network IP that interconnects back to 10.10.10.1 etc.. and then as Patrick stated, it will affect everything in your company... you need to set up DHCP ( or DHCP relay on each of these New Vlans, as well as contend with any expected broadcast traffic etc...

[PS]

I'd like for the VLANs to exist across all three switches. So, for example, I can configure a phone to send tagged traffic and no matter which switch it's plugged into it's always tagged as vlan 11 but still routable to hosts in the default, untagged VLAN.

Am I confusing L2 and L3 operation?

[Patrick_Voss]

Hi PS,

If I am understanding you correctly are you trying to have all 3 switches under 3 different subnets or vlans? If you are trying to change the VLAN structure this would require some pre-planning that will involve your entire network (DHCP, firewall, servers)