ASUS RT-N56U or hardware NAT acceleration


External design and hardware

Firmware upgrade

Web-interface review


Command line interface review




SOHO-segment routers with Gb LAN and even WAN interfaces are no longer a wonder. That’s why when an ASUS RT-N56U wireless router appeared in our lab, we first regarded it as another device for home of small office use where the vendor’s use of Gigabit Ethernet interfaces was only a tribute to fashion. However, RT-N56U specifications and abilities were quite intriguing: the box boasted hardware NAT implementation and it was claimed that the router could simultaneously work in two wireless ranges – 2.4 and 5 GHz. They also claim to have optimized the coverage of the wireless network segment due to intelligent settings of the antenna parameters. However, first things first.

External design and hardware

For its work RT-N56U requires 1.58 A AC at 19 V voltage provided by an external power adapter of a shape not typical for Asus. On it there’s a light voltage indicator and the thing itself has become more handy as it now requires less space in the surge suppressor or in the wall-mounted socket block. Like any telecom equipment we recommend to connect Asus RT-N56U to a UPS to avoid the negative influence of power supply irregularities on the equipment functionality; this is particularly important for Russia and the CIS.

The router itself is performed in a plastic case intended for desktop installation. Mounting on a rack without special shelves is not intended. The RT-N56U case is different from a traditional parallelepiped. The device dimensions with the stand (H*W*D) are 172*145*60 mm and its mass is 330 gr.

The router’s front panel is covered with glossy ribbed plastic and besides the vendor’s name it displays six light indicators of the device status: power supply, the UPS state at 2.4 or 5 GHz, local and global network connections and presence of USB devices. It seems that it was for this multifaceted shiny surface that ASUS RT-N56U was also called Black Diamond.

We should say that such front panel is not unique for ASUS equipment. An external DVD-drive SDRW-08D2S-U boasts the same surface. Unfortunately, the front surface plastic isn’t scratch-resistant, which can slightly damage the device appearance. The back panel is rather ordinary. Here you’ll only find a sticker with information about the device.

On the narrower side there’s a WPS button for simplified connection of wireless clients.

The wider side has five Gigabit Ethernet interfaces (four LAN and one WAN), a power slot, two USB 2.0 ports and a Reset button for resetting configurations to defaults. Light indication of the work of each of the network interfaces is placed next to the port itself and is not visible on the front panel. The shape of the case hides the ports from the user, however, cords originating from these ports stick out. We thought it could be better if the cords went to the back.

RT-N56U’s top and bottom surfaces are actually ventilation grates. The stand is attached to special holes on the router’s bottom panel. The way it got fixed seemed a bit flimsy.

Now let’s look inside the case. Here we’re unable to say anything at all: all electronics is covered with a big screen occupying most part of the board. Information about the CPU can be retrieved only indirectly from the /proc/cpuinfo file which claims that ASUS RT-N56U is built on a Ralink SoC MIPS 74K V4.12 (249.34 BogoMIPS) processor more information about which is presented in the section devoted to the command line interface review. The system employs 128 Mbytes of RAM (/proc/meminfo).

In the box, together with the router you’ll find a 1.5 m patch-cord. We wouldn’t have even noticed it had it not been flat! Naturally, we couldn’t help testing it against standards. However, it passed all tests whose results we present to the reader.

Now let’s study the device software filling.

Firmware upgrade

Firmware upgrade is performed from the Administration – Firmware upgrade tab, where one only has to specify the new firmware image file and to click Upload.

The whole upgrade process takes about three minutes.

A surge arrest during the firmware upgrade process can result in the device firmware inoperability. Then the router gets into the rescue mode. In this case you’ll need the firmware restoration procedure. ASUS RT-N56U can be artificially driven into the rescue mode by pressing the Reset button while the device is turning on until the power indicator starts flashing slowly. This way or the other, the Firmware Restoration utility allows detecting ASUS wireless routers in the rescue mode and uploading new firmware on them.

Now you only have to wait for RT-N56U to boot.

Naturally, we couldn’t help spying (with the help of Wireshark) on the Firmware Restoration utility work. Malfunctioning devices are searched for through a broadcast request to read a file via TFTP. Then the utility uploads the firmware file via TFTP on the device that responded.

Here we could finish the section had it not been for a new feature of installing additional user software that appeared in latest firmware versions. For such installation you’ll need a flash-drive or a USB external hard-drive containing partitions with the EXT3 file system. Unfortunately, NTFS or FAT32 won’t do as all symlinks will disappear after reboot. In Windows such disc can be prepared with the help of Acronis DiskDirector. In operating systems other than Windows different utilities can be used: gparted, fdisk, cfdisk, mkfs and so on. It’s also worth saying that not all firmware branches support this ability. We used the latest versions 7.x.x.x with built-in optware support.

As we’re not the kind of people to choose a soft option, we decided than the partitions will be formatted in EXT3 by the router itself. We created an NTFS partition on a USB-drive and connected it to RT-N56U. Those who are quite happy with how DiskDirector or gparted work can now skip several paragraphs.

Further actions require access via Telnet whose enabling is described in the section devoted to the command line. Let’s make sure that the external drive is connected alright and is visible in the system.

# fdisk -l
Disk /dev/sda: 750.1 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 91202 732571648 7 HPFS/NTFS

First, we create a temporary catalogue /tmp/test/opt and mount it into /opt; then we create the /opt/tmp/ipkg catalogue. Also with the help of the script you have to install ipkg-opt. The whole process is presented below.

# mkdir –p /tmp/test/opt
# mount -o bind /tmp/test/opt /opt
# mkdir –p /opt/tmp/ipkg
# update
Downloading ...
Connecting to (
Updated list of available packages in /opt/lib/ipkg/lists/optware
# install ipkg-opt
Downloading ...
Connecting to (
Unpacking uclibc-opt...Done.
Configuring uclibc-opt...Updating /opt/etc/
Downloading ...
Connecting to (
Unpacking ipkg-opt...Done.
Configuring ipkg-opt...Done.
# ipkg update
Updated list of available packages in /opt/lib/ipkg/lists/optware
Successfully terminated.

Let’s install e2tools for formatting the partition in EXT3.

# ipkg install e2tools
Installing e2tools (0.0.16-3) to /opt/...
Installing e2fsprogs (1.41.12-1) to /opt/...
Installing e2fslibs (1.41.12-1) to /opt/...
Configuring e2fslibs
Configuring e2fsprogs
update-alternatives: Linking //opt/bin/chattr to /opt/bin/e2fsprogs-chattr
update-alternatives: Linking //opt/bin/lsattr to /opt/bin/e2fsprogs-lsattr
update-alternatives: Linking //opt/sbin/fsck to /opt/sbin/e2fsprogs-fsck
Configuring e2tools
Successfully terminated.

Now it’s necessary to unmount the connected disc and format it; however, the disc is already busy.

# umount /dev/sda1
umount: can't umount /media/AiDisk_a1: Device or resource busy

In our case the resource was being used by the minidlna and mt-daapd processes that must be killed before unmounting. If for some reason the disc can’t be unmounted, you can use lsof which will determine which particular processes are employing files on the external drive. After some time, the killed processes might be restarted, so a search for open files can be useful, anyway.

# ipkg install lsof
Installing lsof (4.82-1) to /opt/...
Configuring lsof
Successfully terminated.
# lsof +D /media/AiDisk_a1/
minidlna 1011 admin 6w REG 8,1 372 63 /media/AiDisk_a1/.dms/minidlna.log
minidlna 1011 admin 7u REG 8,1 73728 64 /media/AiDisk_a1/.dms/files.db
minidlna 1017 admin 6w REG 8,1 372 63 /media/AiDisk_a1/.dms/minidlna.log
minidlna 1017 admin 7u REG 8,1 73728 64 /media/AiDisk_a1/.dms/files.db
minidlna 1018 admin 6w REG 8,1 372 63 /media/AiDisk_a1/.dms/minidlna.log
minidlna 1018 admin 7u REG 8,1 73728 64 /media/AiDisk_a1/.dms/files.db
mt-daapd 1034 admin 12uW REG 8,1 12288 67 /media/AiDisk_a1/.itunes/songs.gdb
mt-daapd 1037 admin 12u REG 8,1 12288 67 /media/AiDisk_a1/.itunes/songs.gdb
mt-daapd 1038 admin 12u REG 8,1 12288 67 /media/AiDisk_a1/.itunes/songs.gdb
mt-daapd 1039 admin 12u REG 8,1 12288 67 /media/AiDisk_a1/.itunes/songs.gdb
# killall -9 minidlna
# killall -9 mt-daapd
# lsof +D /media/AiDisk_a1/
# umount /dev/sda1

Now let’s finally format the partition after which we’ll have to change its ID.

# ln -s /proc/mounts /etc/mtab
# mkfs.ext3 -t ext3 /dev/sda1
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
45793280 inodes, 183142912 blocks
9157145 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
5590 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
# fdisk /dev/sda
The number of cylinders for this disk is set to 91201.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): l
0 Empty 1b Hidden Win95 FAT32 9f BSD/OS
1 FAT12 1c Hidden W95 FAT32 (LBA) a0 Thinkpad hibernation
4 FAT16 <32M 1e Hidden W95 FAT16 (LBA) a5 FreeBSD
5 Extended 3c Part.Magic recovery a6 OpenBSD
6 FAT16 41 PPC PReP Boot a8 Darwin UFS
a OS/2 Boot Manager 63 GNU HURD or SysV ab Darwin boot
b Win95 FAT32 80 Old Minix b7 BSDI fs
c Win95 FAT32 (LBA) 81 Minix / old Linux b8 BSDI swap
e Win95 FAT16 (LBA) 82 Linux swap be Solaris boot
f Win95 Ext'd (LBA) 83 Linux eb BeOS fs
11 Hidden FAT12 84 OS/2 hidden C: drive ee EFI GPT
12 Compaq diagnostics 85 Linux extended ef EFI (FAT-12/16/32)
14 Hidden FAT16 <32M 86 NTFS volume set f0 Linux/PA-RISC boot
16 Hidden FAT16 87 NTFS volume set f2 DOS secondary
17 Hidden HPFS/NTFS 8e Linux LVM fd Linux raid autodetect
Hex code (type L to list codes): 83
Changed system type of partition 1 to 83 (Linux)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table

The only thing left is to mount the partition. This can be done manually with the mount /dev/sda1 /media/AiDisk_a1/ command or by rebooting the router, then the external drive will be connected automatically. Let’s do some preparatory works on the EXT3 partition.

# mkdir -p /media/AiDisk_a1/opt
# mount -o bind /media/AiDisk_a1/opt/ /opt/
# mkdir -p /opt/tmp/ipkg
# update
Downloading ...
Connecting to (
Updated list of available packages in /opt/lib/ipkg/lists/optware
# install ipkg-opt
Downloading ...
Connecting to (
Unpacking uclibc-opt...Done.
Configuring uclibc-opt...Updating /opt/etc/
Downloading ...
Connecting to (
Unpacking ipkg-opt...Done.
Configuring ipkg-opt...Done.
# ipkg update
Updated list of available packages in /opt/lib/ipkg/lists/optware
Successfully terminated.

With the help of the built-in vi editor let’s create and files in the /opt catalogue. For this we’ll need the vi and vi commands. The I command is used for entering the input mode, :w – for saving, :q – for exit. Basically, the same result can be obtained by creating text files on the managing host and then copying them to the \\\AiDisk_a1\opt catalogue via SMB or FTP. The created files must be made executable with the help of the chmod command.

# cat
logger -t "" "started [$@]"
[ -z $1 -o -z $2 ] && exit 1
grep -q /opt /proc/mounts && exit 0
mount -o bind $2/opt /opt
/opt/etc/init.d/ start
# cat
logger -t "" "started [$@]"
[ -z $1 -o -z $2 ] && exit 1
grep -q /opt /proc/mounts || exit 0
/opt/etc/init.d/ stop
sleep 1
umount /opt
# chmod +x /opt/
# chmod +x /opt/

Now there’s only one little preparatory thing to complete – make RT-N56U use the created scripts in mounting and unmounting the drive; for this you’ll have to turn to the Advanced Settings tab of the USB Application menu.

Now all primary work is complete; finally we can start installing necessary extension modules. We chose dropbear that provides access to the router via the SSH protocol which we installed and started.

# ipkg install dropbear
Installing dropbear (0.52-5) to /opt/...
Installing psmisc (22.13-1) to /opt/...
Installing ncurses (5.7-1) to /opt/...
Configuring dropbear
update-alternatives: Linking //opt/bin/scp to /opt/sbin/dropbearmulti
update-alternatives: Linking //opt/bin/ssh to /opt/sbin/dropbearmulti
Will output 1024 bit rsa secret key to '/opt/etc/dropbear/dropbear_rsa_host_key'
Generating key, this may take a while...
Public key portion is:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgwCH/rPPJw9F4vYmJ17+DAD/bfYWmDpZ/620kQVvSqUs
PWSZxQETWTUGCVb4B+mmJpuIAruxsrE2x/0XYkAXNRvTW/r7wNa9 admin@RT-N56U
Fingerprint: md5 63:0d:95:24:47:6c:9a:33:68:c8:3b:ae:77:3b:d3:14
Will output 1024 bit dss secret key to '/opt/etc/dropbear/dropbear_dss_host_key'
Generating key, this may take a while...
Public key portion is:
ssh-dss AAAAB3NzaC1kc3MAAACBAOz+QaVnfMEdrZOSfZz4CB7baHURgTQgja0y8f7ccmtV5O1xN2YR
creD97rpLT7Zi9bRZe74jv56vg== admin@RT-N56U
Fingerprint: md5 5d:14:b8:ce:4c:5d:7d:4d:8d:28:fa:f0:eb:4d:02:7a
/opt/etc/init.d/S51dropbear: line 11: pidof: not found
Configuring ncurses
update-alternatives: Linking //opt/bin/clear to /opt/bin/ncurses-clear
Configuring psmisc
update-alternatives: Linking //opt/bin/killall to /opt/bin/psmisc-killall
update-alternatives: Linking //opt/bin/pidof to /opt/bin/psmisc-killall
Successfully terminated.
# dropbear

We made a successful test connection to RT-N56U via the SSH protocol with the help of the PuTTY utility version 0.6.

As SSH access to the router is required even after rebooting the device, let’s configure automatic dropbear start at mounting a partition on an external drive. For this, in vi we’ll create an file in the /opt/etc/init.d catalogue where we’ll specify all necessary utilities for autostart and make it executable. That’s it.

# cat
case "$1" in
kill `cat /var/run/`
# chmod +x /opt/etc/init.d/

Other extensions can be installed in a similar fashion.

Now let’s move on to studying the abilities of the web-interface.

Web-interface review

The ASUS RT-N56U router’s web-interface is typical to this company’s wireless network equipment. We’ve already described it for RT-N15 and RT-N16. That’s why we’re not going to study all its features but will only look at the most interesting of them. For example, on the homepage in the section devoted to wireless settings there’re two independent sub-sections for wireless modules working at different frequency ranges: 2.4 GHz and 5 GHz. Here we’d like to mention the ability to use the AiRadar function for 5GHz frequencies which allows optimizing wireless transmission by focusing transmitted energy on specific sectors, i.e. RT-N56U doesn’t radiate evenly in all directions but only in those where there’re 5Ghz clients.

The web-interface is available in fifteen languages: Chinese, Czech, German, English, French, Malaysian, Danish, Swedish, Portuguese, Polish, Russian, Tai, Finnish, Turkish and Norwegian.

Before studying the Advanced Setting section we’d like to stop at the EzQoS Bandwidth Management item containing two tabs: EZQoS and Traffic Monitor. On the EZQoS page the user can choose preferable traffic streams in exchanging traffic with the global net. If at least one preferred traffic type is chosen p2p application are left with 10% of the channel width determined automatically or manually.

On the Traffic Monitor tab the user can obtain a graph of the internet channel load, of the local, wire and wireless interfaces. The load data can be obtained on the fly, or over the last 24 hours or as a daily log of the last 30 days. We consider this new ability handy, moreover, in some alternative firmware versions this ability has been present for quite a while.

Now let’s turn to the Advanced Setting section containing the following points: Wireless, LAN, WAN, USB application, Firewall, Administration and System Log.

All tabs of the Wireless group allow configuring independent wireless network parameters for 2.4 and 5 GHz frequencies.

The LAN group tabs are rather featureless, besides the multicast routing configuration. Black Diamond can perform the IGMP proxy functions and supports UDP-to-HTTP broadcasting that allows watching IPTV on the devices connected via the wireless channel. It’s possible to specify a gateway address for the clients of a DHCP-server, which is necessary for the cases when RT-N56U broadcasts network settings but is not a default gateway.

ASUS RT-N56U allows connecting to providers with the help of static and dynamic addresses, PPPoE, L2TP and PPTP. The given settings are configured on the Internet Connection tab of the WAN group. Also, we’d like to draw your attention to the Choose IPTV STB Port parameter that allows specifying one or two LAN-interfaces to which a Set Top Box is connected. Such configuration is necessary for those providers who provide IPTV and use separate designated devices.

The QoS tab allows performing finer configuration of the quality of service than the simplified EZQoS system discussed above.

The parameters of Network Neighborhood Share and FTP Share on the router are configured on the respective tabs of the USB Application group. Unfortunately, when the article was being written, ASUS RT-N56U didn’t support Russian in the file names on the built-in FTP-server.

Until now ASUS RT-N56U supported USB connections for printers and external drives only. However, new firmware version provides an opportunity of connecting USB-modems for working in 3G and WiMAX (Yota) networks. Such connection is configured in the Modem item of the USB Application group. The presence of a backup connection will allow you to stay online in case of any problems with the wired provider.

The URL Filter tab of the Firewall group allows filtering content the user receives based on URLs. RT-N56U allows setting up to two time intervals for the filter work.

On the LAN to WAN Filter tab of the Firewall group one can manage permissions for access to the global net from the local one. Besides permitting/prohibiting access via TCP and UDP, the administrator can specify the types of ICMP messages allowed to be transmitted and to state the time when the filter works. Certainly, time on the router must be synchronized.

ASUS RT-N56U wireless router can operate in one of three modes: IP Sharing mode (Default), Wireless Router/IP Sharing mode and Access Point (AP) mode. In ASUS earlier wireless network devices the IP Sharing mode was called Home Gateway. The mode of work is chosen on the Operation Mode tab of the Administration group.

The features the tabs of the System Log group aren’t different from what we saw earlier in ASUS RT-N15 and RT-N16 wireless routers. That’s why we’re not going to stop at them and will move on to the command line interface.


ASUS utility set allows us to search for wireless routers in the net, to restore firmware, to manage downloads, to connect wireless clients or a printer in a simplified mode as well as to help the user in connecting to a specific provider.

The Device Discovery utility searches for ASUS wireless equipment in the local network by broadcasting a UDP-datagram on the 9999 port. The discovered devices are available for configuration in the web-browser.

Firmware Restoration has already been discussed above in the section devoted to firmware upgrade.

ASUS RT-N56U has two USB 2.0 ports to which one can connect external drives or printers. A connected hard-drive or a flash-card can be used for storing data downloaded from the net. Downloads are managed with the help of the Download Master that allows downloading via HTTP, FTP and BT. Downloads are added very easily: you only have to choose a link to the required file or a torrent-file.

Also we decided to connect our ancient Epson Stylus Color 880 ink-jet color printer to RT-N56U. The printer was successfully detected, of which we were informed in the router web-interface.

Now it’s time to start the Printer Setup Utility.

Microsoft Windows 7 x64 SP1 Rus operating system automatically found a driver for the Epson Stylus Color 880 printer and installed it. The whole installation process took no more than two minutes.

Among the utilities there are some that simplify the process of router configuration for working with a specific provider and that of initial configuration of a wireless connection. For this, you can use Router Setup Wizard and WPS Wizard, respectively. Router Setup Wizard detects a connected router and open its web-interface with Quick Internet Setup Wizard already running.

Now let’s see what features are available to the administrator in the command line interface.

Command line interface review

By default ASUS RT-N56U can be accessed via the Telnet protocol. The same account data are used for authentication as in the web-interface. Here it should be mentioned that for new account data to take effect in the web-interface (when the password is changed) you only have to exit it and enter again. However, for the same thing to happen in Telnet access, the device has to be restarted.

Telnet access to the device can be disabled, for which there’s an option “Enable Telnet Server?” on the System tab in the Administration menu.

If the firmware version used lacks the option “Enable Telnet Server?”, then the Telnet server can be enabled on the Main_AdmStatus_Content.asp page known to us from ASUS previous wireless equipment. There you have to enter the commands listed below.

nvram set telnetd=1
nvram commit

Now you only have to reboot the router and connect to it.

After entering correct account data the user gets to the operating system (Linux 2.6.21) command line with a preinstalled BusyBox 1.12.1 library. From now on all unnecessary spaces have been deleted.

RT-N56U login: admin
BusyBox v1.12.1 (2010-12-06 09:58:10 CST) built-in shell (ash)
Enter 'help' for a list of built-in commands.
# cat /proc/version
Linux version 2.6.21 (root@F13) (gcc version 3.4.2) #2274 Tue Dec 7 16:40:44 CST 2010
# busybox
BusyBox v1.12.1 (2010-12-06 09:58:10 CST) multi-call binary
Copyright (C) 1998-2008 Erik Andersen, Rob Landley, Denys Vlasenko
and others. Licensed under GPLv2.
See source distribution for full notice.
Usage: busybox [function] [arguments]...
or: function [arguments]...
BusyBox is a multi-call binary that combines many common Unix
utilities into a single executable. Most people will create a
link to busybox for each function they wish to use and BusyBox
will act like whatever it was invoked as!
Currently defined functions:
[, [[, addgroup, adduser, ash, basename, cat, chmod, chpasswd,
clear, cp, cttyhack, date, delgroup, deluser, dmesg, echo, eject,
expr, find, free, grep, gunzip, gzip, halt, hostname, ifconfig,
insmod, kill, killall, klogd, ln, logger, login, ls, lsmod, mdev,
mkdir, mknod, mkswap, mount, mv, netstat, nslookup, ping, poweroff,
ps, pwd, reboot, rm, rmdir, rmmod, route, sed, sh, sleep, swapoff,
swapon, sync, syslogd, tail, telnetd, test, top, touch, traceroute,
umount, uname, unzip, uptime, vi, wc, wget, zcat

With the help of the ps command let’s see what processes are running.

# ps
1 admin 2596 S /init
2 admin 0 SWN [ksoftirqd/0]
3 admin 0 SW< [events/0]
4 admin 0 SW< [khelper]
5 admin 0 SW< [kthread]
27 admin 0 SW< [kblockd/0]
45 admin 0 SW< [kswapd0]
46 admin 0 SW [pdflush]
47 admin 0 SW [pdflush]
48 admin 0 SW< [aio/0]
609 admin 0 SW [mtdblockd]
675 admin 0 SW< [ksuspend_usbd]
678 admin 0 SW< [khubd]
730 admin 2592 S linkstatus_monitor
738 admin 0 SW [RtmpCmdQTask]
739 admin 0 SW [RtmpWscTask]
746 admin 0 SW [RtmpCmdQTask]
747 admin 0 SW [RtmpWscTask]
779 admin 1448 S /usr/sbin/wanduck
783 admin 1428 S udhcpc -i eth3 -p /var/run/ -s /tmp/udhcpc
788 admin 1448 S /usr/sbin/udhcpd /tmp/udhcpd.conf
792 admin 1064 S dproxy -c /tmp/dproxy.conf
794 admin 1740 S /sbin/syslogd -m 0 -t MST-3MDT -O /tmp/syslog.log
796 admin 1740 S /sbin/klogd
807 admin 0 SW< [scsi_eh_0]
808 admin 0 SW< [usb-storage]
811 admin 1756 S /usr/sbin/infosvr br0
813 admin 2360 S u2ec
814 admin 2360 S u2ec
816 admin 1544 S lpd
819 admin 2360 S u2ec
826 admin 1744 R telnetd
827 admin 1764 S networkmap
829 admin 1476 S rstats
832 admin 2592 S detect_internet
834 admin 3096 S httpd eth3
835 admin 2592 S watchdog
843 admin 2592 S ots
850 admin 1172 S lld2d br0
853 admin 1748 S /bin/sh
911 admin 2592 S usbled
992 admin 1872 S vsftpd
1005 admin 7044 S smbd -D -s /etc/smb.conf
1008 admin 5120 S nmbd -D -s /etc/smb.conf
1009 admin 7044 S smbd -D -s /etc/smb.conf
1011 admin 2480 S ushare
1014 admin 2480 S ushare
1015 admin 2480 S ushare
1016 admin 2480 S ushare
1017 admin 2480 S ushare
1018 admin 2480 S ushare
1020 admin 2480 S ushare
1021 admin 2480 S ushare
1022 admin 2480 S ushare
1023 admin 2480 S ushare
1024 admin 2480 S ushare
1025 admin 2480 S ushare
1026 admin 2480 S ushare
1027 admin 2480 S ushare
1028 admin 2480 S ushare
1029 admin 2480 S ushare
1030 admin 2480 S ushare
1031 admin 2480 S ushare
1032 admin 2480 S ushare
1033 admin 2480 S ushare
1034 admin 2480 S ushare
1035 admin 2480 S ushare
1037 admin 2480 S ushare
1038 admin 2480 S ushare
1039 admin 2480 S ushare
1040 admin 2480 S ushare
1041 admin 2480 S ushare
1042 admin 2480 S ushare
1043 admin 2480 S ushare
1044 admin 2480 S ushare
1045 admin 2480 S ushare
1046 admin 2480 S ushare
1054 admin 1748 S -sh
1056 admin 1744 R ps

Let’s see what files are in the /bin, /sbin, /usr/bin and /usr/sbin catalogues. The vi text editor allows the administrator to create, look through and edit text files right on the router. The top utility will display information about current work of the running processes.

# ls /bin
ac ez-ipupdate ls sed
acl flash mkdir sh
addgroup gpio mknod sleep
adduser grep mount smbpasswd
ash gunzip mtd_write sync
ated gzip mtr tc
brctl hostname mv touch
busybox hw_nat netconf umount
cat igmpproxy netstat uname
chmod iptables ping
cp iptables-restore ps upnpd
cttyhack iwconfig pwd vi
date iwpriv reg wscd
delgroup kill rm zcat
deluser lld2d rmdir
dmesg ln rt2860apd
echo login rtinicapd
# ls /sbin
8367m nmbd
ATE_Get_BootLoaderVersion ntp
ATE_Get_FWVersion nvram_erase
ATE_Get_MacAddr_2G nvram_restore
ATE_Get_MacAddr_5G ots
ATE_Get_PINCode phyState
ATE_Get_RegulationDomain pids
ATE_Get_ResetButtonStatus poweroff
ATE_Get_Usb2p0_Port1_Infor print_num_of_connections
ATE_Get_Usb2p0_Port2_Infor print_wan_ip
ATE_Get_WanLanStatus pspfix
ATE_Get_WpsButtonStatus radioctrl
ATE_Set_AllLedOn radioctrl_rt
ATE_Set_MacAddr_2G rc
ATE_Set_MacAddr_5G reboot
ATE_Set_PINCode refresh_folder_list_all
ATE_Set_RegulationDomain refresh_ntpc
ATE_Set_RestoreDefault reset_to_defaults
ATE_Set_StartATEMode restart_dns
FWRITE restart_networkmap
arpping restart_qos
asuscfe restore
asuscfe_2g rmmod
asuscfe_5g route rtl8367m_AllPort_linkDown
check_proc_mounts_parts rtl8367m_AllPort_linkUp rtl8367m_LanPort_linkDown
convert_asus_values rtl8367m_LanPort_linkUp
create_swap_file run_apps
ddns_updated run_dms
detectWan run_ftp
detect_internet run_ftpsamba run_samba
dosfsck setCountryCode
dumparptable setMAC
e2fsck setMAC_2G
ejusb setMAC_5G
erase setPIN
gen_ralink_config smbd
gen_ralink_config_rt speedtest
getBSSID stainfo
getBootV stainfo_2g
getChannel start3g
getChannel_2g start_ddns
getCountryCode start_mac_clone
getMAC start_ntp
getMAC_2G start_ots
getMAC_5G start_telnetd
getPIN start_usbled
getSSID stop3g
getSiteSurvey stop_dms
getWANStatus stop_ftp
get_sw stop_ftpsamba
getrssi stop_samba
getrssi_2g stop_usbled
getrssi_5g stopservice
getstat swapoff
getstat_2g swapon
gettxbfcal syslogd
gpio_write test_of_var_files_in_mount_path
halt tracktest
hotplug umount2
hotplug_usb_mass usb_path_nvram
ifconfig usbled
init usbtpt
initial_var_file vsftpd
insmod wan-down
ip-down wan-up
ip-up watchdog
klogd wps_oob
ledoff wps_pbc
ledon wps_pin
linkstatus_monitor wps_start
lsmod wps_stop
mdev write
mkswap write_smb_conf
# ls /usr/bin
[ cutter free tail unzip wget
[[ eject killall test uptime
basename expr logger top ushare
clear find nslookup traceroute wc
# ls /usr/sbin
bpalogin httpdcheck ntpclient telnetd usbtest
chkntfs infosvr nvram u2ec wanduck
chpasswd l2tp-control pppd udhcpc
cpubench l2tpd pppoe-relay udhcpd
dproxy lpd rstats udpxrec
httpd networkmap tcpcheck udpxy

We found an interesting cpubench command that allows running tests of the device CPU and memory performance.

# cpubench
This is CPU and memory benchmark for OpenWRT v0.6. This will then take some time
... (typically 30-60 seconds on a 200MHz computer)
Overhead for getting time: 27us
Time to run memory bench: 1.36[secs]
Time to run computation of pi (2400 digits, 10 times): 2.12[secs]
Time to run computation of e (9009 digits): 1.98[secs]
Time to run float bench: 0.00[secs]
Total time: 5.5s
You can copy/paste the following line in the wiki table at:
|| 1970-01-01 || ''Author'' || 1.4s || 2.1s || 2.0s || 0.0s || v0.6 || ''OS'' || ''DeviceModel'' |
| ''CPU model'' || ''CPU Frequency'' || ''LinkToHwPage'' ||

Also, in the /sbin catalogue, there’s a cpu utility that allows displaying the CPU load in percent (the same results can be obtained from the /proc/uptime and /proc/loadavg files).

# cpu
CPU: busy 0% (system=0% user=0% nice=0% idle=100%)

Now let’s have a look at the /proc catalogue and see what files are located here and find out the operating system uptime, its average load, receive information about the CPU and the amount of RAM.

# ls /proc
1 1031 45 811 crypto net
1005 1032 46 813 devices partitions
1008 1033 47 814 diskstats rt3883
1009 1034 48 816 driver scsi
1011 1035 5 819 execdomains self
1014 1037 609 826 filesystems slabinfo
1015 1038 675 827 fs stat
1016 1039 678 829 interrupts swaps
1017 1040 730 832 iomem sys
1018 1041 738 834 ioports sysvipc
1020 1042 739 835 irq timer_list
1021 1043 746 843 kallsyms tty
1022 1044 747 850 kcore uptime
1023 1045 779 853 kmsg version
1024 1046 783 911 loadavg vmstat
1025 1054 788 992 locks zoneinfo
1026 1106 792 Config meminfo
1027 2 794 buddyinfo misc
1028 27 796 bus modules
1029 3 807 cmdline mounts
1030 4 808 cpuinfo mtd
# cat uptime
2393.51 2328.93
# cat loadavg
0.04 0.04 0.00 3/79 1108
# cat cpuinfo
system type : Ralink SoC
processor : 0
cpu model : MIPS 74K V4.12
BogoMIPS : 249.34
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes
ASEs implemented : mips16 dsp
VCED exceptions : not available
VCEI exceptions : not available
# cat meminfo
MemTotal: 126516 kB
MemFree: 13776 kB
Buffers: 5584 kB
Cached: 84628 kB
SwapCached: 0 kB
Active: 26420 kB
Inactive: 68356 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 4600 kB
Mapped: 3796 kB
Slab: 11624 kB
SReclaimable: 2700 kB
SUnreclaim: 8924 kB
PageTables: 524 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
CommitLimit: 63256 kB
Committed_AS: 10416 kB
VmallocTotal: 1048404 kB
VmallocUsed: 4668 kB
VmallocChunk: 1043468 kB

One can find out the list of supported file systems and types of encryption from the /proc/filesystems and /proc/crypto files.

# cat /proc/filesystems
nodev sysfs
nodev rootfs
nodev bdev
nodev proc
nodev sockfs
nodev pipefs
nodev futexfs
nodev tmpfs
nodev eventpollfs
nodev devpts
nodev ramfs
nodev fuse
nodev fusectl
nodev usbfs
# cat /proc/crypto
name : ecb(arc4)
driver : ecb(arc4-generic)
module : kernel
priority : 0
refcnt : 1
type : blkcipher
blocksize : 1
min keysize : 1
max keysize : 256
ivsize : 0
name : arc4
driver : arc4-generic
module : kernel
priority : 0
refcnt : 1
type : cipher
blocksize : 1
min keysize : 1
max keysize : 256
name : sha1
driver : sha1-generic
module : kernel
priority : 0
refcnt : 1
type : digest
blocksize : 64
digestsize : 20

If you have to look into the contents of flash-drives connected to RT-N56U, you can do it in the /shares catalogue subdirectories.

# pwd
# ls

In the /shares catalogue there’s a peculiar redirect_rules file responsible for redirecting incoming connections. For instance, from it, it follows that the built-in server listens not on the 80 TCP-port but on 18017 where data are redirected automatically. You can make sure of this fact by calling netstat showing the ports waiting for connection.

# cat /shares/redirect_rules
-A PREROUTING -d ! -p tcp --dport 80 -j DNAT --to-dest
-A PREROUTING -p udp --dport 53 -j DNAT --to-destination
# netstat -a -e
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
tcp 0 0* LISTEN
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
udp 0 0*
Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 5518 /var/syslogd
unix 3 [ ] STREAM CONNECTED 6456 /var/syslogd
unix 3 [ ] STREAM CONNECTED 6455
unix 3 [ ] STREAM CONNECTED 5524 /var/syslogd
unix 3 [ ] STREAM CONNECTED 5521
unix 3 [ ] STREAM CONNECTED 5430
unix 3 [ ] STREAM CONNECTED 5429

Naturally, we couldn’t but pay attention to the nvram utility that allows looking through and changing the router’s important parameters. We have already fully described its work in the article devoted to the ASUS RT-N16 wireless router. Look at value of the machine_name parameter!

# nvram show | grep http
size: 14838 bytes (17930 left)
# nvram get machine_name

We’d also like to tell you about the fact that the ledon and ledoff in the /sbin catalogue are responsible for turning on and off the led power indicator. This fact is absolutely useless but it’s fun to know anyway.

Here the brief review of the command line interface is over.


The first test we ran was determining the device booting time. ASUS RT-N56U boots in 37 seconds, which seems to be a good result. We also measured the device surface temperature under moderate load. It was 38.6°ะก.

Then we decided to test the router against network attacks. We deliberately started all available services and ran the test from the LAN-segment to maximize the number of detected services. Scanning was performed with the help of a Positive Technologies XSpider 7.7 (Demo build 3100) utility. Altogether we discovered 15 open ports: TCP-21 (FTP), TCP-23 (Telnet), UDP-53 (DNS), TCP-80 (HTTP), UDP-137 (NetBIOS Name), TCP-139 (NetBIOS Samba), TCP-445 (NetBIOS DS),TCP-515 (Printer), TCP-3394 (d2k-tapestry2), TCP-3838 (unavailable), TCP-5473 (unknown), TCP-9100 (unavailable), TCP-9998 (unavailable), TCP-18017 (HTTP) and TCP-49153 (HTTP). The most interesting of the detected insecurities are presented below.

We don’t think these insecurities to be critical.

Now it’s time to measure transmission speeds for which we used a testing stand whose parameters are in the table below.

Component PC Notebook #1 Notebook #2 Notebook #3
Motherboard ASUS P5K64 WS ASUS M60J Asus X55SV ASUS K52Jc
CPU Intel Core 2 Quad Q9500 2.83 GHz Intel Core i7 720QM 1.6 GHz Intel Mobile Core 2 Duo T7500 2.2 GHz Intel Core i3 350M 2.27 GHz
RAM DDR3 PC3-10700 16 Gbyte DDR3 PC3-10700 8 Gbyte DDR2 PC2-5300 2 Gbyte DDR3 PC3-10700 3 Gbyte
NIC Marvell Yukon 88E8001/8003/8010
D-Link DWA-160
Atheros AR8131
Atheros AR9285
Marvell Yukon 88E8055
Intel WiFi Link 5150
JMicron JMC251
Atheros AR9285
Operating system Windows 7 x64 SP1 Rus Windows 7 x64 SP1 Rus Windows 7 x32 Rus Windows 7 x64 Rus

The thing we decided to start with in testing ASUS RT-N56U performance was measuring the rates of wireless transmission between WLAN and LAN segments for both supported frequency ranges: 2.4 GHz and 5 GHz. The results are on the diagram below. We’d like to specifically mention the fact that the tests were run in ordinary home and office environment where there were several wireless networks with low load. For our measurements we took a JPerf 2.0.2 utility. With a unidirectional data stream 25 parallel connections were created; with simultaneous transmission in both directions 15 streams for each direction were created.

High transmission speeds in the 5GHz range can be a result of relative purity of this range whereas at 2.4 GHz frequencies there are many sources of electro-magnetic radiation.

Switching the firewall and port translation (NAT/PAT) on and off results in considerable changes in transmission rates between LAN and WAN interfaces, however, such change is unique for wireless routers. For example, if the function of translating addresses and ports is turned on, the speed triples though typically the situation should be quite the reverse. The thing is that the wireless router at hand has a hardware NAT/PAT accelerator: the packets of an established session are processed by-passing the cpu, by the routing chip. Anyway, ASUS RT-56U is SOHO-segment wireless router and consequently will be mainly used with NAT/PAT turned on. The only thing to be mentioned is that such acceleration can cause problems in the use of IPTV and VPN-tunnels when additional processing by the cpu can be required. The routing speeds via VPN will satisfy most home users whose providers give access to the global net using PPTP as these days Fast Ethernet is normally used for connection and RT-N56U routes data through the tunnel at the medium speed.

Naturally, we decided to check the data transmission speed directly between our test notebooks and the PC. It turned out that the obtained results were caused by the limitations of the testing stand, but not by RT-N56U, i.e. the users will be able to get higher routing speeds using NAT.

We also didn’t forget about the NetBIOS (Samba) protocol access to data located on a Transcend StoreJet 25M3 disc connected via USB. For measurements we took a robocopy utility which is a part of Windows 7. We created two sets of data identical to those used by the Intel NASPT utility in the FileCopyFromNAS and DirCopyFromNAS tests. We placed them on a virtual disc in the RAM to exclude our own disc subsystem from the test. Of course, we wish we could use the full potential of the Intel NASPT utility, however, in many tests with the given wireless router it only produced an error. But as RT-N56U is primarily a router and the storage role is secondary, we decided to compromise and step away from traditional tests. The partitions of the disc connected via USB were formatted in EXT3, NTFS and FAT32. The results of all measurements are on the diagram below.

The obtained transmission speeds of big files from/to RT-N56U for EXT3 and NTFS match those of Fast Ethernet and are a wonderful result for SOHO-segment wireless routers, which unfortunately is not the case for access speeds to numerous small files. We also decided to show the reader the diagram of access speeds to the disc itself.

Here we’re through with testing ASUS R-N56U and will make conclusions.


Finally, we have finished testing a wireless router ASUS RT-N56U. There seems to be an unfortunate tendency that we take too long to write reviews of ASUS equipment; however we hope to overcome it with this vendor’s following devices.

On the whole we were quite happy with the tested wireless router that showed high data transmission speeds. Here are ASUS RT-N56U advantages.

  • Unusual stylish design.
  • High routing and wireless transmission speeds.
  • Simultaneous operation in two wireless ranges (2.4 and 5 GHz).
  • Optimization of wireless coverage for 5 GHz clients.
  • High access speeds to data on a USB-drive.
  • The ability of installing additional extension packages (optware).
  • 3G/4G USB-modems support.

However we can’t but mention some disadvantages of the device.

  • A flimsy stand.
  • Unfortunate location of the cords that spoil the overall design.
  • Crude official firmware.
  • Lack of alternative firmware.

When the article was being written the price for RT-N56U in Moscow online shops was 4800 rubles.

The author and editorial team would like to publicly acknowledge the help of Homutov Vladimir for his technical help.

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0 #1 RE: ASUS RT-N56U or hardware NAT accelerationslim 2019-07-19 01:41
there is alternative firmware from Merlin, but he has recently abandoned this device. I cannot recall who picked up the slack. Merlin's final stable build has a 5ghz bug that leaves wifi open unless you select Enterprise WPA2
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