Asus DSL-N55U ADSL2+ Dual-Band Modem/Router Review

This content is being maintained for reference purposes but is not being updated.


What you get for your money
Configuring the DSL-N55U
Using DSL-N55U with Sky ADSL2+ Broadband Service
IPv6 Connectivity
Traffic Manager and QoS
USB Applications and Media Server
Wireless Configuration
VPN Server – Connecting remotely to your home network
WAN Configuration Options, Virtual Server and DMZ


The Asus DSL-N55U is a router intended for use with ADSL and ADSL2+ services and includes an ADSL modem, rather than the Ethernet WAN port of the very similar RT-N66U router we have also reviewed. The similarity between the two routers extends beyond the black design with the web interface offering almost identical functionality.

The main points on the feature list for the DSL-N55U are:

  • Built in ASDL2+ modem
  • Four Gigabit Ethernet ports
  • Three detachable wireless antenna
  • Two USB sockets
  • Dual band 2.4GHz and 5GHz a/b/g/n wireless networks
  • Support for IPv6
  • Quality of Service controls
  • Media server with support for DLNA, iTunes, FTP, HTTP
  • USB Printer sharing ports
  • 3G/4G dongle backup connection support
  • Built in VPN Server
  • Wireless Guest Network support
Asus DSL-N55U ADSL2+ combined modem/router
Click image for larger version

The 750 Mbps wireless speeds are though the theoretical combination of 300 Mbps (150 Mbps in any single direction) from the 2.4GHz band, and 300 Mbps (150 Mbps in one direction) on the 5GHz band. This is many times faster than ADSL2+ can manage at a maximum of 24 Mbps, but with the media server functionality, buyers of this router are likely to be moving a lot of local LAN traffic around also. The inclusion of two CPU in the device should help avoid heavy LAN traffic impacting on the ability for the router to handle the ADSL/ADSL2+ signals.

This review has been carried out with firmware version and ADSL driver version Running on both a Sky ADSL2+ service, and a BT Wholesale based ADSL2+ service.

What you get for your money

The router retails for around £90 to £100 (October 2012), and the retail box contains the items below.

Asus DSL-N55U Hardware Out Of Retail Box
Click image for larger version
  • Power supply, with interchangeable UK and EU prongs. 19V 1.58A output
  • 3 detachable antennas
  • ADSL microfilter
  • Ethernet cable
  • RJ11 modem lead
  • Router

An unusual inclusion is the flat profile Ethernet cable. There is a paper manual and the usual leaflets, but unless this is your very first router there is very little to be learnt from this paperwork.

Asus DSL-N55U Underside of Router
Click image for larger version

Router manufacturers have largely learnt to include the basic access details for the device on the underside, they also include a reminder to change the routers default username and password of admin. There are two wall mounting screws, but no stand like the RT- N66U.

The power supply (19v, 1.58A output) follows the normal Asus pattern of having a blue LED in it, and the array of LED on the front of the router are bright blue. While LED feedback is very useful the brightness of the Asus LEDs is a bit too much, but then nothing some black tape will not fix.

There is a CD supplied which you can use to configure the router, but this does not work for Mac users, so we will avoid using the CD in this guide.

Asus DSL-N55U Connectors/Ports On Rear Of Router
Click image for larger version

The rear of the router is pretty crowded- perhaps a future design might consider moving the USB ports to the side of the router so that it is less cluttered. The inclusion of a small slider switch to turn off the wireless side of the router is a good addition, though its location next to the power rocker switch means you need to look rather than just fumble behind the router.

Asus DSL-N55U LED Status Panel
Click image for larger version

The nine LED’s on the front of the case usefully include one LED to show when the modem has synchronised to the DSLAM/MSAN in the telephone exchange, and a different LED to show Internet connectivity (this lights up when you have been authenticated with your broadband provider).

The separate 2.4GHz and 5GHz LED’s are useful as you can individually disable these networks via the web interface, and in crowded WiFi areas it would be polite if all your devices support 5GHz to turn off the 2.4GHz signal.

Configuring the DSL-N55U

The router holds your hand nicely when you first connect to it. Ideally we recommend when setting up any broadband hardware to use an Ethernet connection if possible, but the DSL-N55U like many is happy if you use its wireless connection. The default security details are on the label under the router.

As with other Asus networking hardware it does a redirect to the configuration page as soon as you open the web browser, negating the need to know the routers default IP address of or that it can be accessed by the domain name

Asus Router Quick Web Configuration
Click image for larger version

The first step is to configure an administrator password (which is forced by the router), which is a nice step to ensure people do not leave a device on its default settings. While a good idea, there has been little thought put into restrictions, so you can actually set an insecure password that is a single space character.

One other oddity that is common with the Asus RT-N66U is that the stylesheets for the web interface can result in odd looking displays when using Internet Explorer 9. This problem is minor and just means you need to pick a reasonable page size when using Internet Explorer to configure the router.

Asus Router Web Configuration - Internet Setup
Click image for larger version

The router firmware has a list of commonly used settings for around the world, and while it is not a complete list of the UK market, the major options are covered. We did try the Sky MER option but were unable to get it to work, but the Sky LLU line we did try the router on was happy using PPPoA. We elected to use the not listed option for the screenshots in this review.

Asus Router Web Configuration - Manual Settings
Click image for larger version

The router offers PPPoE, PPPoA, MER, Bridge and IPoA options for the authentication protocol. The bulk of this review was done using a BT Wholesale ADSL2+ based service, we also successfully used the router with a Sky LLU service. The settings for a generic BT Wholesale ADSL or ADSL2+ service are VPI 0, VCI 38, Protocol PPPoA, Encapsulation Mode VC/MUX. The next step is to enter the username and password for your broadband connection as supplied by your broadband provider.

Asus Router Web Configuration - Wireless Settings
Click image for larger version

Following the pattern of forcing you to alter the default security settings the next stage of configuration is to specify the security settings for your wireless network. If you wish you can skip this stage, but setting your own strong security key for the wireless encryption is recommended. This is the last stage in the configuration; once the settings are saved you are presented with a summary page letting you do a final double check of all the settings. Once you have confirmed all the settings we arrive at the familiar Asus router home page.

Asus DSL-N55U Main Status Page
Click image for larger version

The similarity with the RT-N66U interface means that many features are identical, so we will try and concentrate on the differences. Once the ADSL service is up and running the first port of call for any new hardware is to see what speed the device has connected at, and for the DSL-N55U this is hidden away down in the System Log.

Asus DSL-N55U ADSL System Log
Click image for larger version

Compared to other features like the traffic manager the interface is relatively crude, but the critical data is displayed, namely the connection speed (Data Rate Up/Down), attenuation and noise margin figures. The performance of the router in terms of ADSL2+ connection is on a par with other good routers.

Using DSL-N55U with Sky ADSL2+ Broadband Service

The Sky ADSL2+ service comes supplied with a router, but both the old Sagem 2504n and the newer SR101 lack the extra wireless features and media server functionality that third party routers can offer.

For Sky customers, while the service requires you to use the supplied router, generally so long as you double check any fault conditions are identical with their supplied router there is little to stop you using your own router. Sky does not normally supply the username and password for the service, but there are several websites where given the MAC address of the supplied routers LAN interface and default wireless key you can obtain the actual username and password.

We duplicated the configuration of the Sky router settings, which on our LLU line were PPPoA, with the standard VPI/VCI of 0/38 and VCMux encapsulation. This did not work, but once we copied the WAN ports MAC from the old Sky router, the DSL-N55U connected to the Sky service with no problems.

Some Sky LLU connections use MER authentication, but we were unable to test this, as the Sky hardware in our local exchange appears to only use PPPoA.

IPv6 Connectivity

The router has support for IPv6 built in, and thus it would be remiss of us to not try and use it. All we can say is that we tried and failed to get IP v6 operating with the router. With other devices it is a pretty simple task of just enabling IPv6 on the WAN interface, but the DSL-N55U has so many options it is clear that the system is not ready for mass market use in that respect.

Traffic Manager and QoS

One of the problems on the sort of ADSL and ADSL2+ connections the router supports is managing the conflicts that arise when one person in a home wants to do something like online gaming which is very latency sensitive while someone else is downloading a large software update. The DSL-N55U provides the router administrator several options to avoid the conflicts that can arise from this conundrum.

Asus DSL-N55U Router QoS and Traffic Manager
Click image for larger version

By default QoS is turned off, so we have turned it on, and fed in our approximate upload and download bandwidth figures. This is the QoS at its simplest level and will rely on a set of automatic rules. For more complicated scenarios you can switch to two manual modes, setting priority rules or full QoS controls.

The default rules are not perfect as we find that if we watched a 1080p YouTube clip, pings still increased from a standard 16 ms to around 80 ms. Though as the configuration page states the rules are setup to really ensure that P2P applications do not adversely impact on web surfing and gaming. So now let us see if we can configure the system to let High Definition YouTube videos still play, but not affect latency.

Asus DSL-N55U Router QoS - User Priority Definitions
Click image for larger version

A little bit of experimenting later and we arrived at the above set of rules, which reserve up to 650 Kbps of our connection for things like ICMP packets, and allowed YouTube streaming which we found via a process of elimination is considered Low priority traffic by the router. 3.87 Mbps is usually just enough capacity to avoid buffering of a 1080p stream. Other streaming services will use different bit-rates, so you will need to experiment also, but we know at least the system works, creating a starting point to build custom rules.

Asus DSL-N55U Router QoS - Traffic Manager With You Tube Clip Playing
Click image for larger version

The above screenshot shows the data coming across the broadband connection when we had implemented our custom rules. Without the QoS rules we had setup, a 1080p clip would normally use bandwidth in the pattern below. The first major peak is actually a thinkbroadband speedtest, followed by the blue which is the colour used to show upstream data. The regular spikes show the YouTube video playing fetching data in batches, which results in spiky latency for other users on this 6.5 Mbps connection.

Asus DSL-N55U Router Traffic Manager
Click image for larger version

The Traffic Manager screenshots show it running in Real-Time mode, but you can switch to a day view which displays the last 24 hours of traffic or you can display the last 30 days of data. The ability to switch between Internet, Ethernet and the two wireless bands is useful when tracking down where your Internet bandwidth is vanishing. The other way to manage Quality of Service is to use the user-defined QoS rules. We have played around to setup a scenario where anyone using BitTorrent will see their speeds limited to 50 Kilo Bytes/second if other traffic needs capacity. These rules also allow you to set different priorities based on the IP address of the client, thus if you pay the bill you could set the rules up so that you got the largest share of the connection when it was busy.

Asus DSL-N55U Router Traffic Manager - QoS User Defined Rules
Click image for larger version

The list of services does not cover every possible permutation, but it is easy enough to add a manual rule, by specifying the source IP/MAC, port, protocol and transfer limits and clicking the ADD(+) button . Port ranges are easily specified e.g. 400:800 covers all ports from 400 through to 800, or if you want to lock down every port <65535 can be used.

USB Applications and Media Server

One of the major features of the DSL-N55U is the two USB ports that allow you to attach various USB storage devices, or just simply charge your mobile phone with a USB charging lead.

Asus DSL-N55U Router USB Application Summary
Click image for larger version

There are some differences compared to the RT-N66U Ethernet router, the Download Master software has been replaced by Media Server software, and the interface makes it clear that 4G USB dongles are supported.

AiDisk and Servers Center

This is identical to the Asus RT-N66U and allows you to configure how data on a USB storage device is shared, including allowing you to make the data available over the Internet. The same dynamic DNS services are supported, so that users on ADSL2+ connections with dynamic IP addresses are not disadvantaged.

Network Printer Server

If you own a USB printer that does not have built-in wireless or an Ethernet port to allow sharing on your home network, you can connect it to a USB port on the DSL-N55U and use either the Asus EZ printer software or the LPR protocol to share the printer between the computers on your network via the router.

Asus DSL-N55U Router Network Printer Server
Click image for larger version

Media Server

If you have a USB storage device installed you can copy onto it the Media Server software which the router will download from Asus.

Asus DSL-N55U Router Installing USB Application Software
Click image for larger version

Installing the software takes around a minute to reach the 99% complete figure, and then seems to sit and wait for a long time, we presume this delay is because it is indexing the USB storage device. So do wait for the installation to complete and be returned to the main USB Application web page.

Asus DSL-N55U Router Media Server Configuration
Click image for larger version

With the software installed you gain the ability to control the options such as the DNLA Media Server that allows you to serve media from the USB device to any DNLA compliant player on your network. Or for those that make extensive use of iTunes, they may want to enable the iTunes server which can act as a repository on your LAN that all your iTunes software can access. The ability to download files using the router directly onto the USB storage device is one major feature missing from the DSL-N55U USB functionality.

Wireless Configuration

The router supports simultaneous use of 2.4GHz (b/g/n) and 5GHz (a/n) wireless networks, and you can configure each independently, restricting your use on the lower band to the slower 20 MHz band to be kinder to other wireless networks in the area, and using the faster 40 MHz band only on the 5GHz band.

Asus DSL-N55U Router Wireless Configuration
Click image for larger version

The back of the router does have a switch allowing you to physically switch off the wireless network, which will save a small amount of power; if you want to disable just one of the bands you need to switch to the professional setting tab.

Asus DSL-N55U Router Wireless Configuration Professional Options
Click image for larger version

To disable the 5GHz band, simply untick the seven check boxes that control when the wireless network is enabled.

VPN Server – Connecting remotely to your home network

The VPN server allows you to configure a username and password that allows someone with a PPTP VPN client to connect to your home network across the Internet.

Asus DSL-N55U Router VPN Server Configuration
Click image for larger version

We have added a user called review with the very insecure password of review, do remember to actually enable the PPTP Server option, as this led to some head scratching initially until we realised we had missed that important step. The more complex details of the VPN are under the VPN Details tab. We have left them at their defaults for the review to keep life simple. Once the settings have been applied, anyone who knows your WAN IP address they should be able to setup a VPN client to connect to the router over the Internet. We then, using a different Internet connection, setup the VPN client in Windows 7.

Screenshots for creating VPN Connection with Microsoft Windows 7
Click on an image to see it in full resolution.

  • Creating VPN Connection in MS Windows 7
  • Creating VPN Connection - How To Connect
  • Creating VPN Connection - Specify Destination
  • Creating VPN Connection in MS Windows 7
  • Creating VPN Connection - Authentication Details
  • Creating VPN Connection - Initiating Connection
  • Creating VPN Connection - Connected

Windows 7 will cycle through various VPN configuration options until it finds the one that matches the server. To speed this up you can alter the properties to restrict the connection to PPTP only. Once connected, you should see the VPN appear in your Network and Sharing Center if using Windows.

The VPN Server does not set a gateway address, so any Internet access will still occur via your primary Internet connection. The VPN allows you access to all network resources on your home network. This is not restricted to file shares, you could connect to the VPN to then gain access to remote desktop on a computer, with the VPN providing an extra layer of security that would not be present if you relied on simple port forwarding rules.


The firewall configuration is the same as the Asus RT-N66U, and beyond the basics of a simple DoS protection system, and the ability to allow ping requests so that tools like our Broadband Quality Monitor will work, the main use of the firewall will be its ability block certain applications from accessing the Internet either completely or based upon a time system.

Asus DSL-N55U Router Firewall Settings Overview
Click image for larger version

To illustrate what you can do with the Network Services Filter, we have setup a blocking rule that should block all Internet access for the computer using the IP address between the hours of 9pm to 9am during the week, and 11pm to 9am at the weekend.

Asus DSL-N55U Router Firewall Example Settings
Click image for larger version

The filter table type allows you to switch to a white list approach, where everything is blocked apart from the specified services. The filter table does provide notes to explain what syntax is allowed for port ranges, but unlike the QoS rules there is no option to filter based on MAC of a particular machine.

WAN Configuration Options, Virtual Server and DMZ

The WAN settings follow the same pattern as the RT-N66U, the main difference is the ability to edit the ADSL connection parameters. The page is pretty long so those who find the need to tweak the router based MTU will need to scroll down, a maximum value of 1492 can be set.

Asus DSL-N55U Router WAN Interface Options
Click image for larger version

The inclusion of DDNS functionality will be welcomed by those people on providers with dynamic IP addresses, and supports both Asus own service and services from,,,, and

Asus DSL-N55U Router Port Forwarding / Virtual Server Configuration
Click image for larger version

The port forwarding allows people running servers to forward the selected TCP or UDP ports to the appropriate machine on their LAN. The local IP field offers a list of the machines that can be seen by the router, or you can manually specify an IP address. Port ranges are supported e.g. 110:130 covers the range 110 through to 130. The famous server and game lists provide settings for the most common applications, and while Xbox Live was listed we found no need to forward any ports to get Xbox Live to work with the router, though if you elect to disable UPnP the situation may well be different.


DSL Settings

The router allows you to force the ADSL mode, picking whether to use ADSL (G.DMT), ADSL2 and ADSL2+ which can be useful if your telephone line is proving to be slightly unstable, as ADSL and ADSL2 modes can for some telephone lines be more stable than ADSL2+.

Save/Restore Router Settings

With the wide range of settings on the router, the ability to backup the settings from the router is very useful. For example once you have got the router working you can backup the config to a file on your computer, and then if you get carried away when playing with the QoS or firewall sections you can quickly restore the router to your original working configuration.

System Logs

The system logs are pretty comprehensive, and in many cases will overwhelm the normal user.

Jan  1 00:00:12 syslogd started: BusyBox v1.17.4
Jan  1 00:00:12 kernel: klogd started: BusyBox v1.17.4 (2012-08-27 15:54:33 CST)
Jan  1 00:00:12 kernel: Linux version 2.6.2219 ([email protected]) (gcc version 3.4.2) #1 Mon Aug 27 16:02:31 CST 2012
Jan  1 00:00:12 kernel:  The CPU frequency set to 500 MHz

Six separate logs are maintained:

  • General Log: General router messages. The file can be saved to disk and be opened using apps like WordPad and TextPad.
  • DHCP Leases: A log of all the DHCP IP addresses handed out since the last reboot.
  • Wireless Log: The details of which wireless channels the router is using.
  • Port Forwarding: Very useful to look to see what ports UPnP is using on your network.
  • Routing Table: The routing rules the router is using, and provides a wealth of IPv6 information.
  • ADSL Log: Only provides the current ADSL connection parameters.


The router in daily use performs very well, and one of the lines used during the review does stress some routers when it is dark and the noise floor rises, which can result in some twitchy modems rebooting several times in an evening. The CPU in the router appears to be up to the task too, as there was not the usual lag in the web interface when playing around with the 3G USB backup modem.

In terms of its ADSL2+ abilities, and how fast the modem pushes the line, it was on par with the Billion 7800N and AVM Fritzbox 7390 in this respect. There is not all the tweakability of these other routers, but the price is a fair bit lower which makes up for this.

A dual band router may seem overkill when the fastest Internet connection supported is 24 Mbps, but with the increasing amount of people running media servers on their LAN, and the presence of one built into the router, the local wireless speed becomes more important.

We tested each wireless band independently, but as they are proper dual bands you can be serving media at full speed on 2.4GHz band, and still have another band able to stream HD material without breaking a sweat.

Our testing setup is our usual one, which makes it easy to compare the results from our various reviews. For those looking to see how the router performs with respect to walls, the testing in the kitchen and conservatory show how the router performs when the signal has to go diagonally through a couple of walls. The measured speed is actually an average measured across a period of 30 seconds.

2.4GHz Wireless Performance
Location Nominal Link Speed Measured Speed
Top Floor - Same room 270 Mbps 82 Mbps
Middle Floor 270 Mbps 65 Mbps
Ground Floor 243 Mbps 38 Mbps
Kitchen 90 Mbps 17 Mbps
Conservatory 1 Mbps 0.1 Mbps
Shed 2 Mbps 0.8 Mbps
5GHz Wireless Performance
Location Nominal Link Speed Measured Speed
Top Floor - Same room 300 Mbps 96 Mbps
Middle Floor 364 Mbps 78 Mbps
Ground Floor 324 Mbps 73 Mbps
Kitchen 80 Mbps 22 Mbps
Conservatory No Signal No Signal
Shed No Signal No Signal

The coverage is pretty much always worse with the 5GHz band on all routers, because the 5GHz is attenuated by building materials more easily, reducing the distance the signal will travel. The range of the 2.4GHz was a little disappointing as we have had better coverage with other devices at the shed.


The DSL-N55U with a retail price in the range £80 to 90 is not the cheapest ADSL2+ modem/router by a long way, and lacks some of the bells and whistles of the more expensive models, but does pack a good performance for its price.

The price point means that you really should be sure of wanting to use the media server or the extensive QoS functionality of the router to make it worth buying. If Asus can add the Download Master functionality that its Ethernet routers support then the router would be even more desirable.


Please click on an image to see it in full resolution.

  • Asus DSL-N55U Router Retail Packaging
  • Asus DSL-N55U Router Retail Box Contents
  • Asus DSL-N55U Router in Retail Box
  • Asus DSL-N55U Router With Wireless Antenna Attached
  • Asus DSL-N55U Router in Retail Box
  • Asus DSL-N55U Router
  • Asus DSL-N55U Router in Retail Box
  • Asus DSL-N55U Router View of Underside and Wall Mount
  • Asus DSL-N55U Router View of Ports at Rear
  • Asus DSL-N55U Router Naked Circuit Board
  • Asus DSL-N55U Router View of Ports on PCB
  • Asus DSL-N55U Power Supply
  • Asus DSL-N55U Power Supply
  • RJ11 ADSL Lead and Ethernet Patch cable
  • Asus Microfilter