Switching and Routing

UDP ports across VLANs


UDP ports across VLANs

I have an issue where a device on VLAN1 needs to send udp packets to Vlan17,
I am not very knowledgeable about networking Vlans but I have tried to use an IP helper address for this.
The UDP ports are: 906, 800, 801, and 1001. This comes from device 10.200.X.X and goes to device 10.16.X.X
Going back the other way UDP ports 905, 1001 and TCP ports 49xxx and 9xxx These should be coming from device 10.16.X.X and going back to 10.200.X.X
The network is comprised of 3 switches that the ports need to traverse.
Switch F1 connects to Switch C1 which connects to Switch W1
Switch F1 is the source of Ports 906, 800, 801, 1001 and start on Vlan1 from 10.200.X.X
Switch C1 is Vlan1
Switch W1 has Vlan1 and Vlan16 goes to 10.16.X.X

I Have on Switch F1 on Vlan1
Ip forward-protocol udp 10.16.X.X 905
Ip forward-protocol udp 10.16.X.X 1001

On Switch W1 on Vlan16
Ip helper-address 10.200.21.X points to the Device on Switch F1 (not the helper for DHCP)
Ip forward-protocol udp 10.200.21.X 1001
Ip forward-protocol udp 10.200.21.X 906
Ip forward-protocol udp 10.200.21.X 800
Ip forward-protocol udp 10.200.21.X 801

This has not worked and I am at a loss of what to do next.

Honored Contributor

Re: UDP ports across VLANs

Simple questions: is IPv4 Routing enabled on your network somewhere? if yes, where? are your switch uplinked to your router device (that could be exactly one of your three involved switches)?

The point is that once your VLANs are IPv4 routed...all IP protocols are routed too...so an host device on VLAN x has IP traffic - being routed - able to reach (Host Firewall policies and ACL apart) host device on VLAN y and vice-versa...no particular settings are necessary switch side.

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Re: UDP ports across VLANs

There is routing enabled in each switch.  Each Vlan has a route ip address. With out anything in the switches the communications do not work.  Prior to moving from a flat network to all of our vlans the system worked but not anymore.


Re: UDP ports across VLANs

Did you configure "ip udp-bcast-forward" globally? Without this command the config "ip forward-protocol udp xxx" on the vlan interface will not work.