SG300-10 VLAN Questions

Question

My apologies if this has been asked before, but I have some questions regarding the setup of my new switch and network. I have never worked with switches before, so this is quite a learning experience. The picture above describes the current layout of my network. Here is how I have tried to set it up, so far.
VLAN 1 [Ports 1-4, Untagged, Trunk] (172.16.1.1/24)
Workstation A (Wired)
172.16.1.2/24
Server B (Wired)
172.16.1.3/24
VLAN 2 [Ports 5-8, Untagged, Trunk] (172.16.2.1/24)
Server C (Wired)
172.16.2.2/24
Server D (Wired)
172.16.2.3/24
Server E (Wired)
172.16.2.4/24
Server F (Wired)
172.16.2.5/24
VLAN 3 [Ports 9-10, Untagged, Trunk] (192.168.1.1/24)
Laptop G (Wireless)
DHCP via Router
Laptop H (Wireless)
DHCP via Router
Laptop I (Wireless)
DHCP via Router
Wireless Router
192.168.1.254/24
Now, my goal is to have all 3 VLANs be able to talk to each other but also have VLAN 1 access the internet, through the wireless router. In the future I would also like Server B to be able to expose services (http & ssh) to the outside. VLAN 2 shouldn't have internet access at all. I know I can add static routes to the wireless router, if need be. All three laptops, can access the internet through the wireless router, without any problems.
So my questions are:
1) Is there anything inherently wrong with the design of this network? If so, what could be changed?
2) Is VLAN 3 really necessary?
3) What would I need to do, to get the 3 VLANs communicating with each other?
4) What should the gateway be, to get VLAN 1 internet access?
5) What would I need to do, to expose Server B services to the outside?
6) What static routes do I need to add?
Thanks in advance!
   Jer

Answer 1

Hello Jeremy,
Thank you for your interest and patience.
You are on the right track here. However, several important changes must be made. Consider the following concepts:
The concept of a native VLAN. The link between the router and the switch must be part of VLAN 1. Otherwise, information from the router will not be distributed correctly on the switch due to the current PVID of 3.
The VLAN IP Interface (VLAN IP Address) identifies the subnet for the VLAN. Therefore, thinking of the switch as a router, you are correct that the default gateway for each client should be the respective VLAN interface on the switch. The switch will automatically route between directly connected IP Interfaces and their subnets.
However, in order for your clients to get to network that the switch doesn't know about, (the internet), there must be a default route to the router.
Additionally, in order for the router to forward information from the internet back to the VLANs on the switch, the router must know how to reach the different VLANs.
The folloing linked figure (Fig. 1) describes an appropriate sample setup. See here.
In this scenario, a SG300-10 is configured with 3 VLANs:
VLAN 1 - Default VLAN, used for management - 192.168.1.x/24 - Ports 9-10 - 1U - Trunk Mode
VLAN 2 - Servers - 192.168.2.x/24 - Ports 5-8 - 2U - Trunk Mode
VLAN 3 - Workstations - 192.168.3.x/24 - Ports 1-4 - 3U - Trunk Mode
VLAN 1 is used to communicate to the router. Therefore, the following default route must be added to the switch's configuration:
ip route      0.0.0.0      0.0.0.0      192.168.1.1
The switch will automatically build the routes between the VLANs local to the switch. Visualize Server C going togoogle.com. Its IP address is 192.168.2.2. Its default gateway should be the VLAN 2 IP Interface on the switch (192.168.2.254 in this example). Because the default route is configured, the switch will forward the internet request to the router. The router will then forward the request to your ISP out the WAN where it will eventually reach Google.
However, when the request comes back into the router, the router must know to route it to the 192.168.2.x subnet. So, in order for this to work, routes that accomplish the following must be configured on your router:
Subnet IP               Mask                    Gateway                                              Interface
192.168.2.1             255.255.255.0        192.168.1.254 (SG-300 IP Interface)         LAN
192.168.3.1             255.255.255.0        192.168.1.254 (SG-300 IP Interface)         LAN
As you have already discovered, there are several limitation to using a router that does not support 802.1Q tagging. Chiefly, your clients will not receive either DHCP or DNS automatically from the router. To mitigate this, you can do either of the following:
Run a DHCP server with multiple DHCP scopes on a device connected to your switch. You can then use Option 82 on the switch to route DHCP requests and DNS info between VLANs on the switch.
Statically configure IP and DNS information. You could enter Open DNS Servers or Google's DNS servers on your clients.
Ideally, you would want to use a router that supports 802.1Q tagging. In this figure here (Fig. 2), you can see the VLANconfiguration page for a Cisco RV180W, a very capable and affordable small business router that I highly recommend. Port 1 on the RV180W is configured as a trunk port and carries VLANs 1-3 to the switch. The clients automatically receive IP addresses and DNS information from the correct DHCP pool on the router.
Do not hesitate to contact us. We are always happy to help.
All the best,
-David Aguilar
Cisco Small Business Support Center
1-866-606-1866