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Hope someone can shed some light here. I have a little network drama which I'm trying to get resolve as soon as possible. To give you a little background;

We have CISCO SG300 small business switches configured in layer 3 We have a CISCO 1921 managed router on site (Managed by the provider) Windows 2012 running DNS/DHCP/AD etc...

Currently our network is configured to have 3 VLANS.

VLAN1 (default data) 10.1.0.xxx/24
VLAN110(VOIP) 10.1.1.xxx/24
VLAN111(Wireless) 10.1.2.xxx/24

Issue is I'm starting to run out of IP address for VLAN1 data range. So I have added another VLAN2 10.1.3.xxx/24 on the router and trying to configure windows 2012 DHCP to have superscope including 10.1.0.xxx & 10.1.3.xxx ranges together to server for data.

However, for some reason I can't seem to get new VLAN2 talking properly. What I have done so far on the switches;

Main switch which is connecting to cisco 1921 managed router, I have tagged the port to VLAN2. Also added VLAN2 and configured IP interface for VLAN2 as 10.1.3.8 on the switch and 10.1.3.253 as gateway. I have all other VLAN1/110/111 ip interfaces configured 10.1.0.8/10.1.1.8/10.1.2.8 respectively.

Here are the settings on the switch for IPv4 interface and routes

From the switch:

Source IP 10.1.0.8 (VLAN1) pinging 10.1.3.8 (VLAN2) – success 100%
Source IP 10.1.0.8 (VLAN1) pinging 10.1.3.7 (VLAN 2 on 2nd switch) – success 100%
Source IP 10.1.0.8 (VLAN1) pinging 10.1.3.251 (VLAN2 current DG on the router) - success 100%
Source IP 10.1.3.8 (VLAN2) pinging 10.1.0.8 (VLAN1) – success 100%
Source IP 10.1.3.8 (VLAN2) pinging 10.1.0.7 (VLAN1 on SWITCH 07) – failed
Source IP 10.1.3.8 (VLAN2) pinging 10.1.0.253 (VLAN1 default gateway on the router) – failed

It seems traffic from 10.1.3 subnet doesn’t know how to get to 10.1.0 subnet on the switch? I may be missing a route?

Any help would be appreciated. Thank you.

1 Answer 1

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Is .8 your default gateway? Otherwise you will not be able to use the L3 switch as a Layer 3 switch. You'll also need a default route to the internet from the switch

You'll also need to configure dhcp relay on the switch and point it back to you server.

Your provider will also need to include the new network in the nat_overload conf so you can access the internet on your new subnet. Another option would be to use your new vlan for non-internet devices, printers yes but copiers (especially scan to email) probably not.

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  • Hi @Jacob Evans, .8 is not my default gateway. On the switch .8 are my IP interfaces for each VLANs. For an example, VLAN1 IP interface is 10.1.0.8. Each VLAN has its own gateway configured on the router. 10.1.0.xxx gateway is 10.1.0.253. 10.1.3.xxx gateway is 10.1.3.253 etc... I have configuerd DHCP relay on the switch to our DHCP server. Also have default routers configured as per my IP4 routers in the original post. Default route to internet is 0.0.0.0 10.1.0.253. Or should I be adding another route?
    – PGP
    Oct 18, 2015 at 21:41
  • There's no reason to have an IP b every subnet if you aren't routing, I would suggest hiring a consultant or doing some more research on routing and sunettting Oct 19, 2015 at 2:08

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