Setting up a wireless Access Point
- Why a homebrew Access Point in the first place?
- Won't this work with YaST?
- And how about NetworkManager?
- Case 1: The open wireless network
- Case 2: Security scheme WEP
- Case 3: Security scheme WPA
- The program hostapd
- Choice of the proper card
- Preparations
- A sensible configuration
- Adjusting for the WLAN card in use
- When the wireless network causes trouble
Why a homebrew Access Point in the first place?
That can be easily explained: Those hardware routers that can be bought may be
suitable for normal users, because they cover a good range of standard
situations, but in some cases they do not suffice any more. They furthermore
can reach their capacity limit, especially in conjunction with many users or
when a high-bandwidth internet link is available – or both in the extreme case.
The other problem is that a hardware router has only a very limited capacity to
act as a server, and most of them cannot handle a LAN divided in multiple
subnets. Here the routing of packets between subnets or from said subnets to
the WAN. Although one
could apply
masquerading to
solve it, but would instead incur other problems.
The third problem is the dependency on the manufacturer designing the firmware
in such a fashion that the router cannot be attacked. Since as a user one
cannot control what features the firmware actually offers and what kinds of
protective measures against any possible attacks it implements, it can be
feasible to set up a wireless router oneself. Any box one can insert a WLAN
card into or already has a built-in WLAN card can serve this purpose.
Another advantage not to be scoffed at: You can extend the capabilities of said
computer as you desire. You may also connect printers to it or set up a proxy
(Squid, wwwoffle, et al.) over which you direct the data traffic to distant web
servers. One could also set up a mail or fax server. You have virtually
unlimited options.
Won't this work with YaST?
This question cannot easily be dismissed, because YaST permits setting it to
master mode. However, when one attempts to configure it as an Access Point, one
quickly discovers a drawback: The security scheme WPA doesn't work!
Disabling encryption or instead switching to WEP instantaneously causes YaST
to readily set up the card, but not so with WPA.
Subsequently loading the configuration file of the WLAN card into an editor and
manually setting the variable WIRELESS_MODE to
master the card is still found to be set up in
managed mode (that is, that it associates with an Access Point).
This is absolutely unsuitable for our purposes and therefore turns out to be
a complete failure. It is therefore imperative to find another method.
And how about NetworkManager?
Here things appear especially bleak. Because NetworkManager has been designed
as a control module on the client side of a network connection and therefore
doesn't provide any modules that set up a WLAN card as an access point, this is
not an option, either.
Your only chance here will be switching to the traditional method using
Hier bleibt Ihnen nur, auf die traditionelle Netzwerksteuerung mittels
ifup/ifdown. This allows
setting up your network card with the help of YaST – thereby incurring a loss
in flexibility as far as wireless networks are converend.
Case 1: The open wireless network
On first glance this is the simplest case imaginable and that can be dealt with
with YaST in virtually no time: There is no need for any information besides
the SSID and the channel number.
There are unfortunately a lot of ramifications in this case that absolutely
have to be taken into account. The first (and at the same time most severe)
problem is that the access point is not secured at all. Which means: Anyone who
knows the SSID (which is no problem at all with a visible SSID, and even a
hidden SSID doesn't provide adequate protection) can associate with the
wireless network and gain access to any resources available to the network
(this can be the connection to the 'Net, but any devices visible within the
LAN can be accessed this way), plus any data transfers in an unprotected
wireless network are in cleartext. Strangers browsing the 'Net via your
connection is by far the least problem that you incur here.
One could argue now that there wasn't anything of interest on one's box and
that protection therefore wouldn't be necessary, but that's far wrong! In the
rarest of cases an intruder is interested in the ata stored on the computer,
but instead the opportunities opened to them for causing mischief totally
anonymously. This can reach from planting malware on you to sending spam from
your Internet connection up to much worse machinations – there's virtually no
limit to one's imagination.
Someone who has connected to your wireless network could attempt to attack a
foreign system to either gain unsolicited access or otherwise sabotage it.
However, other criminal machinations like the distribution of criminally
relevant mqaterial poses a problem: Let's assume a stranger transmits material
containing child pornography via your Internet connection, because he could
effortlessly gain access to your wireless network. When this material shows up
and in consequence investigations are launched, the IP address from which said
material originated will inevitably be found.
A query to the responsible ISP will turn is going to show that this IP address
has been assigned to you at the time in question –
and all the sudden the police rings your bell and presents to you a warrant for
a house search. Now it's extremely hard to know what to do, because now you
have to convince the police officers that you are not
the originator of this material that has been distributed from your connection.
All in all this is only recommended when you want to establish a publicly
accessible hotspot, but then it is absolutely recommended that you arrange for
other safety precautions to impede any abuse, and if need be, simplify the
identification of any perpetrator who abuses your hotspot for racketeering.
That's why I strongly disadvise any private person from this, except when you
know what you are doing here and how you can thwart or at least significantly
impede any misuse.
Case 2: Security scheme WEP
This security scheme (an abbreviation for Wired Equivalent Privacy)
is the original attempt in dealing with the problem with unsecured wireless
networks. In contrast to a cable-bound LAN that, providing properly shielded
cables are used, doesn't emit anything that travels across the wires into the
adjacent space, a wireless network is based on radio waves – which have the
unpleasant property of not being limited in their range. This means that radio
waves don't just stop at a room's boundary, but instead extend beyond that.
The signal may taper off with increasing distance so that it disappears in the
omnipresent background noise, but it is still sufficiently strong to be picked
up outside a building. To put paid to any abuse, WLAN cards have been equipped
with encryption technology that was supposed to make the signal illegible for
foreigners. Therefore WEP has originally been introduced which quickly turned
out to provide insufficient protection.
There are by now methods of attack that are sophisticated enough to crack any
wireless network that is considered protected by WEP within mere minutes. One
simply has to record a sufficiently large amount of data packets to obtain a
sufficiently large base for calculating the WEP key – and if there isn't
enough traffic on said network, one can easily generate oneself it by means of
a brute-force attack
and analyze the reactions.
No matter what, when WEP has been activated, the data traffic on the network in
question is anything but secure. However, this isn't limited to being able to
decrypt any data transmitted in virtually no time – none of the data is
protected against being modified by third parties, with the same weakness of
WEP being responsible for this that also permits an attacker to calculate the
key.
WEP can be used at best to keep out people who aren't well-versed in this
matter. Anyone who can operate the tools needed reasonably well or has gained
sufficient knowledge will hardly be impeded by WEP. Even if such an action is
liable to prosecution, potential attackers won't be deterred by this. In order
to establish a means of security it would be better to give up WEP altogether
and instead set up another scheme for secure connections, for example IPsec.
Since this requires significantly more work (the secure connection has to be
set up and any authorized clients must be provided with the necessary
authorization information), one would very well take a sledgehammer to crack
a nut here. Instead, modern WLAN cards offer a much more usable alternative to
WEP that – given the necessary software – can be set up as easily as WEP, but
in contrast causes a significant increase in security.
In the event that you are interested in WEP and any accompanying ramifications
and security hazards, Wikipedia provides
an article on WEP.
Case 3: Security scheme WPA
This method (an abbreviation for Wi-Fi Protected Access)
that has been defined in the standard IEEE 802.11i exists in two modes, WPA and
WPA2 (WPA is a subset of WPA2 and is considered to provide only limited
protection by now). Whereas WPA still makes use of the architecture of WEP,
although greatly improved and with additional security mechanisms to impede any
attacks on a wireless network, WPA2 further improves security with an entirely
new encryption scheme, which is why WPA2 is generally to be preferred in a
wireless network (in case older devices are used that don't support WPA2 yet,
one has to bite the bullet and also offer WPA, but these end devices should
preferably support the encryption method AES). An intrusion attempt into a
network thus secured turns out to be much more difficult, plus the transferred
data isn't by far that prone to being forged any more as can be done with WEP.
The only drawback: Setting up an Access Point using WPA or WPA2 isn't that easy
compared to WEP (an additional program is required), but hopefully there is a
solution for this problem, too.
Again Wikipedia provides
more detailed information on WPA.
The program hostapd
When YaST refuses to work, the program hostapd
easily steps into the breach – once one has dug through the relatively complex
configuration. From configuring encryption to additional security measures to
access control with the built-in RADIUS server everything is possible; in
essence we are dealing with a Swiss army knife as far as WLAN Access Points
are concerned.
However, the very comprehensive configuration leaves nothing to be desired: You
may set up the WLAN according to your own preferences, but it is essential that
the configuration be put through the acid test. Otherwise it may happen that
hostapd refuses to start, and even if it comes up,
you are denied access although your WLAN is recognized.
It is therefore advisable to start with a minimum configurrátion and modify it
bit by bit. That way it is easily discovered which option causes
hostapd or the WLAN to go on strike and can
therefore be ignored.
If everything is done right, you can enjoy a WLAN Access Point that – according
to the current state of affairs – resists intrusion attempts, but permits
legitimate access without problems.
Choice of the proper card
In order to be able to start in the first place a WLAN card is required. You
will need to find out which chipsets are supported by Linux to begin with.
Unfortunately not every chipset is supported, which means that the affected
cards are out of the question. If at all, they will have to be configured using
the NDIS wrapper, so the question arises whether they can be used for setting
up an access point under Linux in the first place. Fortunately most chipsets
are detected by Linux. This is especially true for those from Atheros, most –
if not all – of the recent chipsets from Intel, but also a great deal of other
manufacturers.
When you possess a suitable card, setting up an access point is not a problem
any more. If need be just search the 'Net for the necessary piece of
information (providing the manufacturer and model name of the card normally
suffices to figure out the chipset in use, and this makes it easy to determine
whether or not the card is detected by Linux) whether you are able to use the
card with Linux. If yes, you may go ahead and plug it into your computer.
When installing the card it is important to discriminate between a PCI and a
USP card. Whereas the latter can simply be plugged into a USB port of your box,
a PCI card requires that you open your computer and put it into a free PCI
slot.
It may also be advantageous when your card comes with an external antenna. In
that case you can, in the event of severe problems with signal propagation,
replace the provided antenna by another one or insert a power amplifier into
the circuit – or even both if need be. Using a much longer antenna can indeed
be worth it when some of your remote stations aren't located in the same plane
as the WLAN card, but in a rather steep angle above it: Because antennas with
a length significantly larger than half the wave length (λ) display a
noticeable increase in steep signal strength you are likely to have a
sufficiently strong signal even when located above the emitting antenna. An
invisible antenna is normally only feasible for any remote stations or you
don't have to transmit to other storys than the one your access point is
located at.
This way even a notebook can be transformed into an access point, especially
when you are connected to your DSL or cable modem by an Ethernet cable and use
the WLAN card as an access point. However, in that case you cannot use it to
connect to other access points, which in turns makes the use of an USB adaptor
mandatory for connecting to other access points or that you configure as your
Access Point instead of the built-in card. You aren't limited in your options
here.
Preparations
Once you have installed the WLAN card, you may immediately check on how Linux is dealing with it. First of all, you should boot your system and log in as root. The network management should already be set to the traditional method (if not, you should make up leeway here). Proceed as follows for this:
- Launch YaST.
- Invoke the module Network devices -> Network settings auf.
- Select the tab Global options.
- Check the box Traditional method using ifup in the section Method for network administration.
- Confirm with Ok.
- Leave YaST.
- Depending on the boot scheme execute one of the following commands:
- Mit System V Init: rcnetwork restart
- Mit systemd: systemctl restart network.service
- In case you are experiencing trouble here, just reboot your box.
Once you have switched the network controls you may set up your network card. This is necessary so that hostapd knows which card it is supposed to control.
- If necessary (may be the case after a reboot), log in as root.
- Launch YaST.
- Invoke the module Network devices -> Network settings. You are automatically placed on the tab Overview.
- See whether the card is automatically detected by YaST and appears in the summary. If yes, select it and click on Edit. Please take a note of the device ID of the network card (you can find it underneath Device in the overview.
- Set up the card. On the first screen you need to assign a static IP address and network mask and click on auf Next.
- Set up the access mode on the next screen. To begin with you need to set it to Managed and set the security scheme to WEP. The fields for the SSID and the passphrase need to be left empty. ¹)
- Complete the setup until you return to the overview screen and confirm by clicking on Ok.
- Don't leave YaST yet!
¹) You might wonder now what this nonsense is supposed to be. However, this definitely has a reason: By setting the card to Managed you prevent others from connecting to your access point during the brief period that has your access point completely without defense, and an empty SSID prevents your network card from associating with a foreign access point. This setup is going to be changed completely by the program hostapd so that you finally wind up with what you expect.
This makes the WLAN card known to the system and generally operable. However, you don't have an access point yet, because it has to be properly configured to begin with. Some additional steps are required for this:
- In YaST invoke the module Software -> Software Management.
- In the textbox enter the term hostapd. Then select the package..
- (optional) When you want to dynamically assign IP addresses within your WLAN you also need a DHCP server. In this case enter dhcpd in the textbox and then select the pcket of the same name.
- Confirm your choice with Ok and accept any additional packets that are required for your choice.
- Leave Yast afterwards..
When you intend to dynamically assign IP addresses within your WLAN you need
to set up your DHCP server first. Read the correspondent manpages on how this
is done. An explanation on how to do this would exceed the scope of these
instructions.
In case you don't want that you can immediately go ahead and set up
hostapd.
A sensible configuration
In order to use the card you need to know its interface identifier. This is
required for hostapd so that it knows which card it
is supposed to manage. You should have already determined it while installing
the card, otherwise iwconfig can be of help here.
Then you may start to properly set up your Wifi
card.
Minimum configuration for a wireless Access Point | |||
---|---|---|---|
Parameter | Description | Value(s) | Recommended |
interface | The interface managed by hostapd Please note that this identifier may vary depending on your distro and card in use. |
The identifier of the card e. g. wlann Replace n with the device number. |
The previously determined identifier |
driver | The driver to be used by hostapd. Normally it is recommended to choose nl80211 as the driver to be used. Please note that, depending on the driver chosen, you don't have all options available. The choice none is of no interest for us. |
hostapd, madwifi, nl80211, bsd, or none | nl80211 |
ssid | Sets the SSID of your WLAN (that is, its identification). | String of characters | The desired identifier |
country_code | Set this parameter to the country code of your current location (written
in capital letters). For the United States you need to enter US, for the
United Kingdom GB, etc. This value determines which transmission power and frequencies the Wifi card may use according to the respective national policies (Radio Regulations and any laws and regulations). |
The country code applicable for you | e. g. US |
ieee80211d | Is your Wifi adapter supposed to advertise any information on the set country code as well as all permissible frequencies and transmission powers? | 0 or 1 | 1 |
hw_mode | Determines the mode of operation of your Wifi card. Please keep in mind to only specify any modes that are actually supported! | a: IEEE 802.11a (11 MBit/s at 5 GHz) b: IEEE 802.11b (11 MBit/s at 2.4 GHz) g: IEEE 802.11g (54 MBit/s at 2.4 GHz) ad: IEEE 802.11ad (7 GBit/s at 60 GHz) |
b |
channel | The number of the channel to be used in respect to the mode of operation ATTENTION: This setting is not fixed! Although the access point is going to occupy the desired channel it may switch to another frequency and thereby avoid interferences in case it detects a collision with another station. |
0 = unset > 0 = Channel number |
e. g. 6 |
preamble | Use a short preamble? This can increase performance when transmitting with a maximum bandwidth of 11 MBit/s (transmission mode IEEE 802.11b). In order for this to be used any remote stations must know how to handle a short preamble or this feature is disabled if necessary. |
0 or 1 | 1 |
auth_algs | Authentication algorithms to accept This is a bit field that specifies which authentication algorithms hostapd is to accept. IEEE 802.1X is providing for two variants, Open authentication and authentication with pre-shared keys. Bit 0: Open system authentication Bit 1: Pre-shared key (requires WEP) Depending on the desired algorithms you need to set this value accordingly. Bit 1 needs to be set only when you intend to use WEP (which is not recommended). |
Bit field depending on the desired algorithms | 1 |
ignore_broadcast_ssid | Make the SSID of your WLAN publicly visible or not? For maximum security it is recommended that the SSID be invisible, and in case the field length is set to zero as well there isn't even the slightest clue on what the SSID could be. However, it could be that some remote stations cannot handle this, making it necessary to have the field length set to the length of the SSID even though the SSID itself isn't transmitted. |
0 = SSID visible 1 = SSID invisible, with field length 0 2 = SSID invisible, with field length = length of SSID |
1 |
eap_server | Make use of the built-in EAP server? This is necessary only when you intend to use any advanced authentication options without having to resort to an external RADIUS server. This normally isn't necessary for home use. |
0 or 1 | 0 |
wpa | Use WPA? This value is a bit field that specifies which variant of WPA to use. Bit 0: WPA Bit 1: WPA2 Only WPA2 should be offered for maximum security. However, this could incur problems with older remote stations, because they don't know how to talk WPA2. In this case it is necessary to additionally enable WPA, however, then AES should be used as encryption algorithm instead of TKIP. |
Bit field depending on the desired variants | 2 |
wpa_passphrase | The passphrase securing the WLAN | Passphrase | Desired passphrase |
wpa_key_mgmt | Secure access according to which scheme? | WPA-PSK, WPA-EAP, WPA-PSK-SHA256, or WPA-EAP-SHA256 | WPA-PSK |
wpa_pairwise | Which encryption algorithm to use for WPA? You may specify different algorithms as a space-separated list here. This value is only necessary when you have enabled WPA. |
TKIP or CCMP | CCMP |
rsn_pairwise | Which encryption algorithm to use for WPA2? You may specify different algorithms as a space-separated list here. This value angeben. Dieser Wert ist nur dann notwendig, wenn Sie WPA2 aktiviert haben. |
TKIP or CCMP | CCMP |
wps_state | Enable Wi-Fi Protected Setup? This permits easily incorporating other devices into an existing network with the help of a PIN or by pushing a button. Caution! By now some flaws have been discovered in WPS that permit an attacker to gain unsolicited access to the WLAN! Therefore WPS should best be avoided and additional stations be manually added instead! |
0, 1, or 2 | 0 |
Even with this minimum configuration your wireless Access Point is operable in
next to no time. All that is left is to activate it.
Depending on the boot scheme used execute the following commands:
- System V Init:
- insserv hostapd
- rchostapd start
- systemd:
- systemctl enable hostapd.service
- systemctl start hostapd.service
When you invoke iwconfig afterwards you are going to
find that the Wifi card you just set up has been set to Master mode. Now you
have reached your goal and can start using your WLAN without any problems.
However, the Wifi card operates according to the specification IEEE 802.11b
now, which covers many older cards. All modern cards are capable of handling
a transmission rate of 11 MBit/s at 2.4 GHz, therefore you cannot foul anything
up here. Anyone who wants more power has of course appropriate options at his
disposal.
Adjusting for the WLAN card in use
Depending on your Wifi card you have additional options at your disposal. This
can be e. g. an increased transmission bandwidth (all modern Wifi cards
definitely support IEEE 802.11g, and a great deal of cards also provide
IEEE 802.11n as well). The standard IEEE 802.11g offers a maximum bandwidth of
54 MBit/s, which means a significant increase in throughput in comparison to
IEEE 802.11b, and IEEE 802.11n further increases bandwidth and offers higher
transmission power.
On top of that modern cards offer extended security measures that can be used
by hostapd, but the transmission and management
modes can be adjusted as well without any problems.
Because plenty of cards support IEEE 802.11g by now it is likely that you may
switch to said mode. This can be done by changing one single parameter, and if
your card supports IEEE 802.11a as well you may enable it here, too.
Modified parameters for IEEE 802.11g | ||
---|---|---|
Parameter | New value | Notes |
hw_mode | g | Modification in case IEEE 802.11a isn't supported |
hw_mode | ag | Possible modification when IEEE 802.11a is supported as well |
In case of IEEE 802.11n things are quite similar, except that you have some
additional settings at your disposal. With a bandwidth of 150 MBit/s or higher
alternatively on 2.4 or 5 GHz (the latter providing the card supports
IEEE 802.11a) you gain an additional increase in throughput.
In order to use IEEE 802.11n, activate the following additional parameters in
the config:
Settings necessary for IEEE 802.11n | |||
---|---|---|---|
Parameter | Description | Value(s) | Recommended |
ieee80211n | Enables IEEE 802.11n mode of the Wifi card. WARNING: When you activate this although your card doesn't support IEEE 802.11n hostapd will refuse to work and you won't be able to use your wireless Access Point! |
0 or 1 | 1 |
ht_capab | Defines various parameters for IEEE 802.11n. In case nothing is provided,
a minimal set of features is enabled. WARNING: In case you activate any features not supported by your card hostapd will refuse to work and you won't be able to use your wireless Access Point! Therefore enable these features one by one and see whether hostapd still starts up and you are able to connect to your access point. If not, just remove the feature in question from the list. |
Possible features are: [LDPC] [HT40-] or [HT40+] [SPMS-STATIC] or [SPMS-DYNAMIC] [GF] [SHORT-GI-20] [SHORT-GI-40] [TX-STBC] [RX-STBC1], [RX-STBC12], or [RX-STBC123] [DELAYED-BA] [MAX-AMSDU-7935] [DSSS_CCK-40] [PSMP] [LSIG-TXOP-PROT] |
[HT40+][SHORT-GI-20][SHORT-GI-40] |
require_ht | Is IEEE 802.11n mandatory? If yes, any stations that don't support this
mode are denied access. When no stations that still rely on IEEE 802.11g are used in this WLAN you may set this to 1. |
0 or 1 | 0 |
wmm_enabled | This must be enabled for IEEE 802.11n to function properly! | 0 or 1 | 1 |
In the meantime the standard IEEE 802.11ac provides yet another increase in performance of wireless networks (so-called gigabit WLAN) which uses the band at 5 GHz that is rarely used (if at all) by WLAN cards. In order to use this functionality you need to set these additional parameters:
Für IEEE 802.11ac notwendige Einstellungen | |||
---|---|---|---|
Parameter | Description | Value(s) | Recommended |
ieee80211ac | Enables IEEE 802.11ac mode of the Wifi card. |
0 or 1 | 1 |
vht_capab | Defines various parameters for IEEE 802.11ac. In case nothing is provided,
a minimal set of features is enabled. WARNING: In case you specify any features not supported by your card hostapd will refuse to work and you cannot access your wireless Access Point! Therefore enable these features one by one and see whether hostapd still starts up and you are able to connect to your access point. If not, just remove the feature in question from the list. |
Possible features are: [MAX-MPDU-7991] or [MAX-MPDU-11454] [VHT160] or [VHT160-80PLUS80] [RXLDPC] [SHORT-GI-80] [SHORT-GI-1600] [TX-STBC-2BY1] [RX-STBC1], [RX-STBC12], [RX-STBC123], or [RX-STBC1234] [SU-BEAMFORMER] [SU-BEAMFORMEE] [BF-ANTENNA-2] [SOUNDING-DIMENSION-2] [MU-BEAMFORMER] [MU-BEAMFORMEE] [VHT-TXOP-PS] [HTC-VHT] [MAX-A-MPDU-LEN-EXPn] (n ∈ {0,1,2,3,4,5,6,7} [VHT-LINK-ADAPT2] or [VHT-LINK-ADAPT3] [RX-ANTENNA-PATTERN] [TX-ANTENNA-PATTERN] |
[VHT160-80PLUS80][SHORT-GI-80][SHORT-GI-160] |
require_vht | Is IEEE 802.11ac mandatory? If yes, any stations that don't support this are denied access. | 0 or 1 | 0 |
wmm_enabled | This must be enabled for IEEE 802.11ac to function properly! | 0 or 1 | 1 |
vht_oper_chwidth | Specifies whích channel width the Wifi card is supposed to use | 0: 20 or 40 MHz 1: 80 MHz 2: 160 MHz 3: 80 + 80 MHz |
2 |
Please keep in mind that the range of your WLAN signal becomes increasingly
less the broader the transmission channel becomes! Because the entire power
used for the signal spreads across the entire channel width, the signal
spectrum becomes more shallow and thus disappears earlier among the
atmospheric background noise
present! In addition any
interfering signals
have a broader window for interfering with the connection. It may further occur
that the signal that you are picking up
fades
because of bad propagation conditions and is therefore more difficult to
receive.
Also keep in mind that any obstacles on the signal path (walls, vegetation,
etc.) cause additional signal loss and so additionally reduce its range and
that metalliferous obstacles can cause deadspots without any reception at all
on the far side in relation to the access point!
That's why the transmission rate can, depending on local conditions, deviate
more or less downwards! The transmission rate stated in the product description
refers to (almost) ideal conditions – a condition met all too rarely.
When the wireless network causes trouble
There are many causes for problems with a wireless network. However, these
don't just encompass faulty configurations, but various technical problems can
also play tricks on you.
However, these problems can usually be solved rather quickly.
What fails to function? | ||
---|---|---|
Problem | Cause | Solution |
The WLAN is inactive. |
|
|
The WLAN cannot be reached. |
|
|
The connection fails. | The signal is too weak or is interfered with. You may be too far away from
the access point or are located in a disadvantageous angle in relation to it
(this is the case every time the access point and a remote station are located
in different storys). Please note, too, that all walls between the access point
and the remote station cause additional signal loss, thereby decreasing its
range even further. Furthermore any signals of stations operating on the same frequency are jamming each other, thereby causing interferences (this can quickly become true in densely populated areas). Another source of interferences are switch-mode power supplies whose parasitic frequencies can severely affect WLAN routers and thus cause a connection breakdown. |
Try one (or more) of the following measures:
|
The transmission bandwidth is too low. | When stations interfere with each other it may happen that they are reducing the transmission bandwidth by themselves in order to allow all stations to continue operating. This phenomenon normally occurs in areas covered by many active WLANs. | Apply the same measures recommended for a failing connection (except for a power amplifier, because using one here would only make things worse). |