DHCP to Multiple VLANS via SG200-50P

[andyoeft07]

Here's my scenario.  A client of mine is an executive office suite.  Each office gets its own internet via a separate router.  This is a big jumble of cabling and confusion.  I want to streamline this by using a single router that feeds a single DHCP subnet to a  SG200-50P switch confgured with multiple VLANS. I've been able to accomplish this by connecting an ethernet cable from the router to each VLAN group of ports.  So VLAN1 has 4 ports, the first is connected to the router.  VLAN2 has 4 ports, the first is connected to the router etc.    Each VLAN is successfully getting DHCP, AND I am isolating traffic between VLANs.  There is no cross=pinging between VLANS, which is what I want.  And each VLAN can access resources within its VLAN and access the internet too.  Bravo   HOWEVER, I'd like to provide DHCP to all the VLANS over a single switch port, rather than using a router feed for each VLAN port grouping.  Since my router is limited to 4 ports, I'm limited to 4 VLANs.  I need 12.   I'm assuming this is accomplished by trunking all the VLAN's to a single port.  But I've not managed to accomplish this.  Any ideas are much appreciated.

[Tom Watts · Accepted solution]

Hi Andy, this depends what any of your routers support. The switch supports 802.1q. One of your routers will need to support a trunk or sub interfaces with 802.1q capabilities. This is very important for more than just DHCP. Since using a single wire, all vlans except the native vlan will not have internet access unless the router can understand the vlan tags.

My advice to you is first identify the capability of your routers, find out which router you have/want that supports 12 vlans and 802.1q. The configuration should be the easy part.

-Tom
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[andyoeft07]

Yes.  It does appear that 802.1Q is the special sauce that makes trunking work.  I'm using a Cisco RV016 router.  It appears that this router supports up to 13 VLANS on a per-port basis, as I have since discovered since my first post  The RV016 has 16 ports.  Three are dedicated to WAN1, WAN2 and DMZ.  But the RV016 does not support 802.1Q.  Which means my only solution is the one I've outlined in my first post.  Each VLAN port on the RV016 needs to be wired to the first corresponding port of the VLANs on the SG200-50P, which I believe will suffice for my needs.  It makes ongoing changes to VLANs a little more difficult since, as my client's tenants come and go, I'm going to have difficult time keeping individual VLAN ports contiguous.  I'll simply need to document more carefully. 

[Tom Watts]

Andy, the good thing is, you may make multiple subnets within the RV016 and you can set up an external DHCP server which can support the DHCP scopes. It shouldn't be too painful unless the DHCP server is a kink in the works.

-Tom
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[andyoeft07]

When you say multiple subnet, are you suggesting that I can create mutliple subnets with separate IP address schemes, (172.16.1.x, 172.16.2.x) within the RV016 or subnets based on scope ranges from a single IP address scheme.   When referring to an external DHCP server, are you referring to the RV016 or something like a LInux or Windows server?

[Tom Watts]

On the router, the default IP address is 192.168.1.0 subnet. The router will issue DHCP for this subnet. The router cannot support additional DHCP scopes. However, you may configure "multiple subnets" so you may connect different devices with different IP addresses to the router provided you have configured the multiple subnet field with the desired subnet and they will get to the internet and work.

Referencing the DHCP server, you would need something like a Linux or Windows server.

-Tom
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