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I have two Netgear GS748Tv5 switches behaving strangely.

I have a Router that feeds a switch with multiple subnets. That switch is VLANed and is working fine and everything connected to it currently can join the subnets as expected. I need to have these two new switches in a rack so that I can feed these subnets to devices in the rack.

The strange behavior:

Once I split 40 of the 48 ports into five different VLANs only the first set of eight ports will allow connected devices to connect to the gateway for that subnet. All other VLANs will not allow a device to get a DHCP address.The VLANs are setup according to Netgear's instructions and besides that caveat seem to be working correctly. Devices connected to the VLAN can ping each other other, but can never reach the broader network. Devices Not connected to the same VLAN cannot talk to each other. I have tried setting up just 2 8 port VLANs in the middle of the switch using say ports 20-36 and still only the first eight ports in the configuration will allow connection to the gateway. I cannot find anyone else having this issue and in my limited experience there is no reason this shouldn't work.

P.S. The VLANs are setup entirely without tags.

JonathanDavidArndt
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Kevin Gardenhire
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    You need to tag frames on the trunk to the router. The router will have multiple virtual interfaces (one for each VLAN), and it should be connected to the switch with a trunk. – Ron Maupin Feb 08 '18 at 21:05
  • If your trunk and tag settings are all correct then, connect to one of the VLAN’s with a valid IP address andtroubleshoot from the VLAN back to the DHCP server on one of the trouble VLANS. You have something in the pipe that is preventing DHCP traffic on those VLANS. – Marcus Patman Feb 08 '18 at 21:56

1 Answers1

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DHCP addresses aren't supplied by a VLAN, they're supplied by a DHCP server that is connected to the VLAN.

Accordingly, you need to make sure that the VLAN includes the DHCP server (unless you're using DHCP relaying). If this DHCP server is the router you need to either connect each VLAN to a router port set up for the VLAN or use 802.1q tags on a VLAN trunk. The trunk needs to be configured in the same way on the switch and on the router. One VLAN can be untagged, all others must be tagged.

Devices connected to different VLANs can't communicate with each other (that's the point of VLANs) unless connected by a router. Usually, you set up rules on the router to control that communication between VLANs.

Zac67
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