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The Graveyard - Products No Longer Supported => Hubs and Switches => DGS-1216T => Topic started by: FVaseghi on November 30, 2016, 10:00:44 PM

Title: Setting up vlan on dgs-1210-28 with DHCP relay?
Post by: FVaseghi on November 30, 2016, 10:00:44 PM
I have DGS-1210-28.
Port #1 connected to a router and other connected to Desktops and other switches.
I want to setting up 2 VLAN  with DHCP relay from my router?
How i do that?
This setting not worked:
802.1Q VLAN:
VID      VLAN Name      Untagged      
1      Default         01-8,15-16
2      VLAN1         9-11
3      VLAN1         12-14
DHCP Relay State : Enabled
DHCP Relay Agent Information Option 82 Remote ID: User Define - Router Mac Address
DHCP Local Relay Status: Enabled and Disabled tested
Config DHCP Local Relay for VLAN: All Mode Tested.


Please help me.
Title: Re: Setting up vlan on dgs-1210-28 with DHCP relay?
Post by: FurryNutz on December 05, 2016, 06:43:15 AM
Link>Welcome! (http://forums.dlink.com/index.php?topic=48135.0)

Title: Re: Setting up vlan on dgs-1210-28 with DHCP relay?
Post by: PacketTracer on December 06, 2016, 03:59:45 AM

I refer to the device's manual found here (ftp://ftp2.dlink.com/PRODUCTS/DGS-1210-28/REVC/DGS-1210-28_REVC_MANUAL_4.20_EN.PDF), assuming your device is hardware revision C (?)

First, my understanding based on this manual is that the DGS-1210-28 is a pure L2 device without any L3 functionality - hence your setup does not allow any routing between the networks defined via VIDs 1, 2 and 3. As a consequence devices attached to VLAN1 (VID 2, ports 9-11) and VLAN2 (VID 3, ports 12-14) will be isolated within their VLAN: There is only a peer-to-peer communication possible within the two peer groups defined by {PC1,PC2,PC3} and {PC4,PC5,PC6} respectively. Is this the communication pattern you want to have?

If your plan was to allow PC1-PC6 to talk (=to be routed) to destinations beyond their VLAN limits, you have a wrong setup: In this case either use a L3-capabale switch or configure your DGS-1210-28 to directly connect VLAN1 and VLAN2 to your router (e.g. via a VLAN trunk for VIDs 2 and 3 at port 1, given the opposite router port can be configured correspondingly).

But given you really want to have this isolated communcation scenario, be aware that due to lack of L3 functionality, your DGS-1210-28 does not provide a standard compliant DHCP relay agent (at least as far as my understanding is from reading the manual) because this would require the ability to define a per VLAN IP interface that can be assigned to a VLAN specific instance of a DHCP relay agent and that is used by that instance to contact (route to) configured DHCP servers (residing anywhere in a routed network) via IP unicast.

Instead the switch seems to adopt the "vlan-mod-port" method based on DHCP option 82: It listens for DHCP requests on the VLANs you specified via the "DHPC Local Relay Settings" (in your case the "DHCP/BOOTP Local Relay VID List" should consist of VIDs 2 and 3, and "DHCP/BOOTP Local Relay Status" should be set to "Enabled"), includes its relay IP address (= System interface address) and DHCP option 82 (with suboptions CID and RID) and uses its "System" interface to contact configured DHCP servers reachable via VLAN VID 1 (in your case your router's IP address which you should have configured as "Server1" for interface "System" within "DHCP/BOOTP Relay Interface Settings").

The important thing here is that your DHCP server residing in your router has to be able to handle DHCP option 82 accordingly: It should allow the configuration of DHCP pools and IP address assignment policy based on the IP address of the relay agent (your switch's IP address) and particularly on the CID option containing the VLAN and port information for the port the original DHCP request arrived at the switch (the RID suboption should be irrelevant in your case). Does your DHCP server (=router) provide such functionality?