Looking for ways to flash and test a router with less cabling and PC IP conf changes

I am a novice at all of this, but I am hacking/building/deploying images to a test router. Right now I am painfully changing cables around and changing the IP config on my PC during each cycle. Is there a better way? Here is more detail.

This is what I do today and note my normal LAN subnet is

  • change code, build on dev PC to create image
  • The test router is connected over serial, in this case the bootloader has TFTP but hard codes to a tftp server IP
  • Unplug eth from PC and plug into test router. Change IP on PC to static IP of Run tftp2 as a tftp server on the PC
  • Run bootloader commands to tftp image from PC and boot test router. Openwrt boots to with DHCP on.
  • change IP conf on PC to be DHCP which gets a 192.168.1.x IP from the test router
  • after done testing, unplug PC from test router back into normal router and dhcp renew to get back on the normal LAN

I am wondering if could avoid the cable changes and PC IP changes by using a stable router between the PC and the test router. Here are the goals.

  • No cabling changes
  • No IP configuration changes on my PC
  • Ability to copy images built on PC (on normal) LAN to be TFTP-ed to the router looking for a tftp server.
  • Can admin the newly flashed test router that will have the default openwrt config via Luci and SSH from the PC on the normal LAN
  • The newly flashed openwrt test router does not attempt to be a DHCP server on the normal LAN
  • Allow test router to run it's own network but FW-ed off of the regular one

So far my ideas have been to cable the stable router [lan port] <-> [lan port] test router and use a VLAN/interface and a TFTP server on the stable router for Then maybe a VLAN with FW rules to allow admin of newly flashed router on but otherwise isolating the test router from the normal network. This would require a switch/port change between VLANS on the stable router to avoid cable changes but that is fine.

Are there simplier and/or better ways to handle this. I won't be shocked!


Multiple, fixed IP addresses on the host/build machine

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Connect your PC to the test VLAN, either by using VLAN tags between stable router and PC,
or by adding a second NIC and cable to the PC (the stable router might not be needed in the latter case).

I hacked together a way to make this work. I am sure there are some holes in it, but it works well for me. The key is it allows a bunch of build/flash cycles with no cable changes. Here are the main parts in case it is helpful for anyone else. If you specific questions let me know.

I am using one stable router (SR) and a development router (DR) I am creating builds for and flashing. All of the "magic" is just config on the SR. Basic cabling with ports like this

                                            | Dev        |
                                            | Router     |
                                            | (DR)       |
                                            |            |
           +------------+                   |            |
           | Stable     +-VLAN DR-------LAN-+            |
           | Router     |                   +------------+
           | (SR)       |
+-----WAN--+            |
           |            |                   +------------+
           |            +-LAN---------------+ PC         |
           +------------+                   |            |
                                            |            |
                                            |            |
                                            |            |
                                            |            |

Key parts. This is all on the stable router

  • New interface, VLAN, and FW zone for the dev router port
  • Interface: 2 static IPs
  • which is what the bootloader on my dev router looks for with TFTP
  • which I used as it is in the subnet of a default openwrt build but outside default dhcp range. Note the rest of my network is NOT 192.168.1.x
  • Setup TFTP, which is under dnsmasq
  • Set WAN type FW rules for the VLAN DR Interface. I think the most key parts are
    • LAN => VLAN DR accept all
    • VLAN DR => any - Reject, Accept (output), Reject
    • traffic rules
      • Allow PING, and DNS from VLAN DR to all other zones
      • Allow TFTP from DR to SR router
      • Allow HTTP/HTTPS forward from DR out through LAN on SR - this allows opkg list refreshs etc

My build/deploy steps. Note I am using a usb/serial connection from the PC to the dev router

  • Build openwrt on PC
  • scp bins to stable router in the location TFTP runs from
  • reboot dev router (have serial connection console on PC) and stop in boot loader
  • TFTP bin from stable router to dev router
  • boot dev router

At this point I can SSH to the dev router, HTTP - Luci etc from the PC.

  • can flash the bin using the openwrt site if you want etc

The dev router will not automatically be able to route/dns to the internet, but if you do the following to tell it the stable router is DNS and the default gateway it will