3Com 3CRWER100-75

This device is NOT RECOMMENDED for future use with OpenWrt due to low flash/ram.
DO NOT BUY DEVICES WITH 4MB FLASH / 32MB RAM if you intend to flash an up-to-date and secure OpenWrt version onto it! See 4/32 warning for details.

1) This device does not have sufficient resources (flash and/or RAM) to provide secure and reliable operation.
This means that even setting a password or changing simple network settings might not be possible any more, rendering the device effectively useless. See OpenWrt on 4/32 devices what you can do now.

2) OpenWrt support for this device has ended in 2022.
19.07.10 was the last official build for 4/32 devices.

ASAP I' ll try to improve this article. Now here is step by step installation of OpenWrt for experienced user. NOT for beginners.

Version/Model Launch Date S/N OpenWrt Version Supported Model Specific Notes
- - - trunk r28395 -
CPU Ram Flash Network USB Serial JTag
Atheros 2315A@180MHz 16MiB 4MiB 1 + 4 No Yes ?


Other SW

You are doing everything at your own risk! Nobody is responsible for what you are doing. Don't do it if you don't know what you are doing! Incomplete BETA version of text!

Operating system

  • Set your IP: (alt.
  • Mask:


  • Start server listening on: (alt.


  • Telnet to (alt. on port 9000 to get Redboot prompt
  • It's better to use .bat (Because port open only 1 second)
  • You can use some usefull script from https://gist.github.com/shayas/
putty.exe -telnet -P 9000
goto redboot 


  • Verify config ( last point where you can stop the procedure )
fconfig -l
  • Clear flash
fis init
  • Agree with format
  • Download kernel from TFTP server
load -r -b %{FREEMEMLO} openwrt-atheros-vmlinux.lzma
  • Create partition for kernel
fis create -r 0x80041000 -e 0x80041000 vmlinux.bin.l7
  • Download RootFS from TFTP server
load -r -b %{FREEMEMLO} openwrt-atheros-root.squashfs
  • Check free space
fis free
  • Create partition for RootFS. Replace 0x2E0000 for number you get as difference between last number of free space and the first number. All in hex.
fis create -l 0x2E0000 rootfs
  • Verify partition table
fis list
  • Reboot into OpenWrt


  • Telnet to on standard port(23)
  • If it does not work try:

1) Telnet to (alt. on port 9000 to get Redboot prompt

RedBoot> fis load -l vmlinux.bin.l7
RedBoot> go 0x80041000 

2) Now you can see Open Wrt promt.


3) Thus you have to correct booting procedure. Reboot device

Telnet to
RedBoot> fconfig -l 
RedBoot> fconfig boot_script_data

Enter following:

fis load -l vmlinux.bin.l7
go 0x80041000

Save and reboot.


  • brown = gnd
  • red = tx
  • orange = rx


Port Switch port Router's port label Interface
LAN Port 0 LAN 4 eth0.1
LAN Port 1 LAN 3 eth0.1
LAN Port 2 LAN 2 eth0.1
LAN Port 3 LAN 1 eth0.1
WAN Port 4 Cable/DSL eth0.2
CPU Port 5 N.A. eth0

To find out the dev switch name:

root@OpenWrt:~# swconfig list
Found: switch0 - eth0

To check the switch ports list:

root@OpenWrt:~# swconfig dev switch0 show
Global attributes:
        enable_vlan: 1
        name: IP175C
        phy: 0
        reg: 0
        val: 12544
Port 0:
        status: up, 10 Mbps, full duplex, auto-negotiate
        link: 10
        tagged: 0
        pvid: 1
Port 1:
        status: down, auto-negotiate (in progress)
        link: 0
        tagged: 0
        pvid: 1
Port 2:
        status: down, auto-negotiate (in progress)
        link: 0
        tagged: 0
        pvid: 1
Port 3:
        status: down, auto-negotiate (in progress)
        link: 0
        tagged: 0
        pvid: 1
Port 4:
        status: up, 100 Mbps, full duplex, auto-negotiate
        link: 100
        tagged: 0
        pvid: 2
Port 5:
        status: up, 100 Mbps, cpu port
        link: 100
        tagged: 1
        pvid: 0
        vid: 1
        ports: 0 1 2 3 5t 
        vid: 2
        ports: 4 5t 
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  • Last modified: 2021/04/03 17:28
  • by brunorf