Forum Discussion

Aspirant

Jun 07, 2018

M4100 DHCP over VLAN eating packets

I have the following setup: pfSense Firewall -> Cisco Switch (servers) -> Cisco Switch (users) -> M4100-D10e -> Cable Modem The pfSense firewall does the routing and NAT and is VLAN aware...

Installation

Troubleshooting

mwgmwg

Aspirant

Jun 12, 2018

The pfSense firewall cannot be physically located where the cable modem comes into the building. They are about 800 feet apart and connected via fiber.

I have not tried setting it up in 'static', I'm not sure what that means exactly. But I'm sure it would work if I can make the switch a dumb layer-2 switch with vlan support.

JohnC_V

NETGEAR Employee Retired

Jun 12, 2018

mwgmwg,

Then you can just create a port-based VLAN in order for it to work. You can set all the specific members with U or Untag then set the PVID to its corresponding VLAN ID.

Regards,

mwgmwg
Aspirant
Jun 20, 2018
That's what I have already. I know how to use the VLAN tagging on the switch, and it's working fine. It's doing something with the IGMP DHCP Messages being sent through the VLAN trunk, such that they're not re-broadcast to the port where the Internet bridge is on. It seems like's its intercepting the messages, and re-transmitting them locally, but never sends them back. I want it to just pass the IGMP broadcast messages like normal.

Trouble is, there are SO many options on this switch for how to handle IGMP, and I'm not sure which ones are enabled by default, and where to turn those off.
- schumaku
  Guru - Experienced User
  Jun 21, 2018
  Where should IGMP play a role in IPv4 DHCP? BOOTP/DHCP does make use of UDP IP broadcast - source 0.0.0.0, destination 255.255.255.255 with UDP on port 67 resp. UDP port 68 - for DHCP discovery, DHCP offer, and DHCP request, the final DHCP does make use of the assigned IP addresses. No IGMP Mulicast at all.
  - mwgmwg
    Aspirant
    Jun 21, 2018
    Sorry, you're correct about IGMP. I've been out of networking for awhile now.. Are there any settings on the switch that might prevent DHCP UDP broadcasts across a VLAN trunk ?