[beasty]

Thank you. I will do that
and let you know how I get on


EDIT:

This is now the output of nvram show | grep vlan.*ports

size:
vlan2ports=1 5
vlan0ports=4 3 2 1 5*
vlan3ports=4 5
20776 bytes (11992 left)

[beasty]

oh I rebooted the router a second time and got this output

vlan2ports=1 5
vlan0ports=4 3 2 1 5*
vlan3ports=4 5
vlan1ports=0 5

[Per Yngve Berg]

vlan4 and 5 disappeared.

Forgot to remove ports from vlan0

nvram set vlan0ports="1 5"

Reuse vlan 0 rather than vlan 5.

[beasty]

I think what I will do at this point is come back to the issue in a few months. During that time I hope to research ip tables and look further into DD-WRT so that I, myself, understand better and if I cannot get to the bottom of the problem I will at least be a lot more knowledgeable than I am now and will probably make another thread in a few months or come back to this one.

Thanks for your help, all who replied. You have given me enough knowledge and direction to study more on a couple of networking subjects and have given me a fair understanding of what is going on.
Hopefully in a couple of months I will be able to write a decent little manual on how to achieve the solution to the problem for people with the same approach and router, but at the moment I feel I should do some work to understand ip tables fully for myself

[Alozaros]

here are some useful VLAN commands (Broadcom only) and their default outcome
on my R7000 (Broadcom)

nvram show | grep vlan.*ports

vlan2ports=0 5u
size: 41254 bytes (24282 left)
ping_ip=nvram show | grep vlan.*ports
vlan1ports=1 2 3 4 5*

nvram show | grep port.*vlans

port5vlans=1 2 16
size: 41254 bytes (24282 left)
port3vlans=1
ping_ip=nvram show | grep port.*vlans
port1vlans=1
port4vlans=1
port2vlans=1
port0vlans=2

nvram show | grep vlan.*hwname

size: 41255 bytes (24281 left)
ping_ip=nvram show | grep vlan.*hwname
vlan2hwname=et0
vlan1hwname=et0