Using DD-WRT as a managed switch with VLAN trunk

Use old Linksys router as VLAN switch 

You can find lots of cheap Linksys E900, E1200, and E4200 at Goodwill that can be repurpose to use as mange network switches with VLAN trunk and tagged access ports.

You don't get much capability for the trouble but it's good enough for simple lab testing or adding some IOT devices with VLAN tag.  Here is what you will have after this procedure.

• 2 trunk ports
• 2 access ports with VLAN tag
• One remaining port for switch management
• Virtual WIFI with VLAN tag

The general procedures is:

• Flash DD-WRT firmware.
• E900/E1200 link.
• E1200 link.
• Setup the device as a basic managed  switch
• Add VLAN tag
• Tag 2 ports with VLAN

Ref:  DD-WRT Switched Ports settings

System Reset

Note that after any system reset using the reset button, the LAN ports do not work and access to the router is limited to WIFI only.  It will be completely open so you can connect using WiFi then do the steps below to activate LAN ports access.

• Connect via WIFI (it will be open)
• Reset admin password
• Go to Setup - Networking - Assign to Bridge - Add br0 to interface vlan1.
• Save then Apply Setting
• At this time, set the Local IP address to desired IP to work with local router.
• Optional setup main Wireless SSID and password, save and apply change.

Setup AP device as managed switch

Setup switch to work with a LAN router IP 192.168.10.1

• Connect via LAN port and login to AP
• Setup - Basic Setup
• WAN connection type:  Disabled
• Set router name
• Network Setup, Router IP
• Local address 192.168.10.11
• Gate way : 192.168.10.1
• Local DNS:  192.168.10.1
• Optional:  Assign WAN port to switch - set check box
• Setup NTP client, set server IP to the main router if it has NTP setup already
• Save Setting
• Setup - Advanced Routing - Operating Mode:  Router.
• Service - Services 
• Disable DNSMasq
• Enable Telnet
• Disable ttraff Daemon
• Setup - Networking
• Assign to bridge - add br0 to interface vlan2
• Security - Firewall:  Disable
• Set Filter Multicast
• Setup - Basic Setup
• Disable DHCP server
• Save and apply setting

Connect to main router, test to make sure can access AP from any connection from main router.

Add VLAN

Add VLAN and setup trunk ports

• Telnet in to box as root with admin password
• Create new vlan name
• nvram set vlan3hwname=et0
• nvram set vlan4hwname=et0
• nvram show | grep vlan.*hwname | sort
• nvram commit
• reboot
• Use web interface to create trunk on port 1,2 to vlan 3,4
• Save and apply settings
• Telnet to box and add vlan to trunk port
• nvram set vlan3ports="2 0t 1t 5*"
• nvram set vlan4ports="3 0t 1t 5*"
• nvram commit
• reboot

NVRAM configuration summary:

port0vlans=2 18 19 21

port1vlans=3 4 16 18 19 21

port2vlans=3 4 16 18 19 21

port3vlans=3 18 19 21

port4vlans=4 18 19 21

port5vlans=2 3 4 16

---------------------

vlan0ports=1 2 3 4 5*

vlan1ports=0 1 2 3 5*

vlan2ports=4 5

vlan3ports=2 0t 1t 5*

vlan4ports=3 0t 1t 5*

------------------------

Add virtual WiFi

Use wireless menu to add virtual WIFI to use with a VLAN

Create bridge to link virtual WiFi to VLAN

On E4200, need extra startup command to make WiFi with VLAN work.

• Use Administration - Command menu, enter these commands
• sleep 20
• stopservice nas
• wlconf eth1 down
• wlconf eth1 up
• wlconf eth2 down
• wlconf eth2 up
• startservice nas
• Save Startup 
• Management - reboot