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Mesh Network ​

For testing GL-MT3000 by GL-inet. Nothing special about this router other them we have them laying around the lab and OpenWRT (open source linux-based firmware) supports it.

Flash OpenWRT ​

If the router is running the factory firmware you have to flash OpenWRT into it.

  1. Get the Sysupgrade image from the OpenWRT website of this router.
  2. Flash the image. Go to the admin dashboard under 192.168.8.1 and look the firmware upgrade page (typically System → Upgrade / Local upgrade) and upload the OpenWrt sysupgrade .bin. IMPORTANT Uncheck "Keep settings".
  3. Done. Start the upgrade and let it reboot.

First OpenWRT Boot ​

After flashing, OpenWrt is typically at 192.168.1.1 (so you may need to reconnect / renew DHCP).

  1. Open LuCI by opening a broser and typing 192.168.1.1 then set a password immediately.
  2. Wi-Fi may be disabled by default on fresh OpenWrt: go to Network → Wireless and enable/configure SSIDs.

Setup (Basic) Mesh ​

802.11s mesh on (usually) 5 GHz as the backhaul between routers, and normal AP Wi-Fi on each router for your phones/laptops (clients don’t join 802.11s directly).

Install mesh related packages:

opkg update
opkg remove wpad-mini wpad-basic wpad-basic-wolfssl wpad-basic-openssl wpad-basic-mbedtls 2>/dev/null
opkg install wpad-mesh-openssl

Create the 802.11s mesh backhaul (both routers):

  1. LuCI → Network → Wireless
  2. On the 5 GHz radio: Add a new wireless network
  • Mode: 802.11s
  • Mesh ID: pick a name like beryl-mesh
  • Network: lan (this is what “bridges” the mesh into your LAN)
  • Wireless security: set WPA3-SAE (or “SAE”) + a strong key
  • Channel: set a fixed channel (same on both!) — don’t leave it on “auto”
  1. Save & Apply

Now create your usual AP SSID(s) on each router (2.4 GHz and/or 5 GHz):

  1. Same SSID name, same security, same password on both routers
  2. Attach them to the LAN network

This is how phones/laptops connect — the 802.11s part is just the hidden backhaul.

IMPORTANT

At this point the mesh network is not ready due to all router have the DHCP server enable and will produce problems.

VRRP over Wi-Fi/mesh ​

Using VRRP we get:

  • Router A management IP: 192.168.1.2
  • Router B management IP: 192.168.1.3
  • Router X management IP: 192.168.1.X
  • Shared "floating" gateway IP (VIP): 192.168.1.1 and clients use 192.168.1.1 as gateway/DNS
  • keepalived moves 192.168.1.1 between routers and runs a hook to start/stop DHCP.
  1. Give each router a unique management IP on LAN
  • IPv4 address: 192.168.1.X
  • Netmask: 255.255.255.0
  1. Install keepalived on all routers
opkg update
opkg install keepalived
opkg install luci-app-keepalived
  1. Configure VRRP + the floating IP in /etc/config/keepalived
config globals 'globals'

# The floating IP object
config ipaddress 'vip_lan'
        option address '192.168.1.1/24'
        option device 'br-lan'
        option scope 'global'

# VRRP instance
config vrrp_instance 'lan_vrrp'
        option name 'LAN'
        option interface 'br-lan'
        list virtual_ipaddress 'vip_lan'
        option virtual_router_id '51'
        option advert_int '1'
        option nopreempt '1'
        option auth_type 'PASS'
        option auth_pass 'ChangeThisPassword' # CHANGE ME
        option state 'MASTER' # CHANGE ME
        option priority '120' # CHANGE ME
  1. Make DHCP start only on the VRRP MASTER (OpenWrt hook). Edit the file /etc/keepalived.user
#!/bin/sh
# OpenWrt calls ONLY /etc/keepalived.user via hotplug on state changes.

act="${ACTION:-$1}"
act="$(echo "$act" | tr 'a-z' 'A-Z')"

case "$act" in
  NOTIFY_MASTER|MASTER)
    /etc/init.d/dnsmasq start
    [ -x /etc/init.d/odhcpd ] && /etc/init.d/odhcpd start
    ;;
  NOTIFY_BACKUP|NOTIFY_FAULT|NOTIFY_STOP|BACKUP|FAULT|STOP)
    /etc/init.d/dnsmasq stop
    [ -x /etc/init.d/odhcpd ] && /etc/init.d/odhcpd stop
    ;;
esac
chmod +x /etc/keepalived.user
  1. Prevent DHCP accidentally starting at boot (all routers).
/etc/init.d/dnsmasq disable
# optional but recommended if you use IPv6 RA/DHCPv6:
[ -x /etc/init.d/odhcpd ] && /etc/init.d/odhcpd disable
  1. Start/enable keepalived (all routers)
/etc/init.d/keepalived enable
/etc/init.d/keepalived restart
logread -e keepalived

Experimental Setup ​

Metrics:

  • curve like: distance → (RSSI/SNR, packet loss, throughput, jitter, failover time)
  • Radio link metrics (RSSI, bitrate/MCS if available)
  • Connectivity metrics (ping loss/latency)
  • Throughput metrics (iperf3 up/down)

Router Experimental Variables ​

Fix variables (all routers):

  • Mesh band: 5 GHz (or 2.4)
  • Fixed channel (same in all), fixed width (start 80 MHz; if flaky, test 40 MHz as a separate experiment)
  • Fixed transmit power (don’t leave “auto” if your build exposes it)
  • Disable extra clients during test (no phones connected, no scanning if you can avoid it)

Record routers settings:

uci show wireless | sed -n '1,200p'
iw dev

TBA: [Add more information....]

External Reading Resources ​