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  • Computer Networks UNISA - Chap 8 &ndash; Wireless Networking

    - by MarkPearl
    After reading this section you should be able to Explain how nodes exchange wireless signals Identify potential obstacles to successful transmission and their repercussions, such as interference and reflection Understand WLAN architecture Specify the characteristics of popular WLAN transmission methods including 802.11 a/b/g/n Install and configure wireless access points and their clients Describe wireless MAN and WAN technologies, including 802.16 and satellite communications The Wireless Spectrum All wireless signals are carried through the air by electromagnetic waves. The wireless spectrum is a continuum of the electromagnetic waves used for data and voice communication. The wireless spectrum falls between 9KHZ and 300 GHZ. Characteristics of Wireless Transmission Antennas Each type of wireless service requires an antenna specifically designed for that service. The service’s specification determine the antenna’s power output, frequency, and radiation pattern. A directional antenna issues wireless signals along a single direction. An omnidirectional antenna issues and receives wireless signals with equal strength and clarity in all directions The geographical area that an antenna or wireless system can reach is known as its range Signal Propagation LOS (line of sight) uses the least amount of energy and results in the reception of the clearest possible signal. When there is an obstacle in the way, the signal may… pass through the object or be obsrobed by the object or may be subject to reflection, diffraction or scattering. Reflection – waves encounter an object and bounces off it. Diffraction – signal splits into secondary waves when it encounters an obstruction Scattering – is the diffusion or the reflection in multiple different directions of a signal Signal Degradation Fading occurs as a signal hits various objects. Because of fading, the strength of the signal that reaches the receiver is lower than the transmitted signal strength. The further a signal moves from its source, the weaker it gets (this is called attenuation) Signals are also affected by noise – the electromagnetic interference) Interference can distort and weaken a wireless signal in the same way that noise distorts and weakens a wired signal. Frequency Ranges Older wireless devices used the 2.4 GHZ band to send and receive signals. This had 11 communication channels that are unlicensed. Newer wireless devices can also use the 5 GHZ band which has 24 unlicensed bands Narrowband, Broadband, and Spread Spectrum Signals Narrowband – a transmitter concentrates the signal energy at a single frequency or in a very small range of frequencies Broadband – uses a relatively wide band of the wireless spectrum and offers higher throughputs than narrowband technologies The use of multiple frequencies to transmit a signal is known as spread-spectrum technology. In other words a signal never stays continuously within one frequency range during its transmission. One specific implementation of spread spectrum is FHSS (frequency hoping spread spectrum). Another type is known as DSS (direct sequence spread spectrum) Fixed vs. Mobile Each type of wireless communication falls into one of two categories Fixed – the location of the transmitted and receiver do not move (results in energy saved because weaker signal strength is possible with directional antennas) Mobile – the location can change WLAN (Wireless LAN) Architecture There are two main types of arrangements Adhoc – data is sent directly between devices – good for small local devices Infrastructure mode – a wireless access point is placed centrally, that all devices connect with 802.11 WLANs The most popular wireless standards used on contemporary LANs are those developed by IEEE’s 802.11 committee. Over the years several distinct standards related to wireless networking have been released. Four of the best known standards are also referred to as Wi-Fi. They are…. 802.11b 802.11a 802.11g 802.11n These four standards share many characteristics. i.e. All 4 use half duplex signalling Follow the same access method Access Method 802.11 standards specify the use of CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to access a shared medium. Using CSMA/CA before a station begins to send data on an 802.11 network, it checks for existing wireless transmissions. If the source node detects no transmission activity on the network, it waits a brief period of time and then sends its transmission. If the source does detect activity, it waits a brief period of time before checking again. The destination node receives the transmission and, after verifying its accuracy, issues an acknowledgement (ACT) packet to the source. If the source receives the ACK it assumes the transmission was successful, – if it does not receive an ACK it assumes the transmission failed and sends it again. Association Two types of scanning… Active – station transmits a special frame, known as a prove, on all available channels within its frequency range. When an access point finds the probe frame, it issues a probe response. Passive – wireless station listens on all channels within its frequency range for a special signal, known as a beacon frame, issued from an access point – the beacon frame contains information necessary to connect to the point. Re-association occurs when a mobile user moves out of one access point’s range and into the range of another. Frames Read page 378 – 381 about frames and specific 802.11 protocols Bluetooth Networks Sony Ericson originally invented the Bluetooth technology in the early 1990s. In 1998 other manufacturers joined Ericsson in the Special Interest Group (SIG) whose aim was to refine and standardize the technology. Bluetooth was designed to be used on small networks composed of personal communications devices. It has become popular wireless technology for communicating among cellular telephones, phone headsets, etc. Wireless WANs and Internet Access Refer to pages 396 – 402 of the textbook for details.

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  • intel wireless ac 7260 not working

    - by Johally Sanchez
    I just installed ubuntu 14.04 lts in my new laptop (asusq502la) I need help to make my wireless card already look at additional drivers but don't appear anyvdriver in there. Also I already download the drivers from intel and tried this http://wireless.kernel.org/en/users/Drivers/iwlwifi but it doesn't work either I hope someboy can help me rfkill list all show this 1: asus-wlan: Wireless LAN Soft blocked: no Hard blocked: no 2: asus-bluetooth: Bluetooth Soft blocked: yes Hard blocked: no sudo modprobe iwlwifi doesn't show anything it just ask for the password. dmesg | grep iwl still doesn't show anything.

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  • How to enable wireless on my hp compaq nx6110 laptop

    - by victor
    My laptop is an old HP Compaq NX6110. The wireless switch is not working, and I can`t also enable wireless from connexion manager. I connected to to the Internet with Ubuntu using wired LAN, and I downloaded windows wireless drivers, Wi-Fi radar application, and additional drivers. I also updated to Ubuntu 11.10 but still no luck. I guess I need some terminal commands. Any ideas are welcome. Thank you for the attention victor.

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  • Connect to new wireless network

    - by Shawn de Wet
    Wireless networking was working perfectly on my old adsl router. Then I moved to a new home that does not have adsl, and the router has been replaced with a new 3G one. I have worked through the following links: Connecting to a wireless network and http://ubuntuforums.org/showthread.php?t=571188 I have set the router from it's default WPA-PSK encryption to WEP encryption and also to No Encryption. But when I get to dhclient -wlan0, I keep getting No DHCPOFFERS received. Yet the 2 windows machines in my home connect fine to this wirelesss network (in all encryption settings). If I try iwlist scan I can see that the wireless network is indeed visible. Where do I start scratching to see where the problem may lie.

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  • Help making TP-Link Wireless USB Adapter TL-WN723N work consistently

    - by Savvas Katseas
    I've only recently made the jump to Ubuntu, using 11.10/64 as my only desktop OS. Everything seems to be working fine, except my USB Wireless adapter, TP-Link's TL-WN723N which is randomly connecting and disconnecting. The connection time appears to be random, too: I've experienced hours of connectivity and lots of connections/disconnections. I've tried searching for a solution, but what I find doesn't concern this specific USB adapter. I'd like some help identifying the problem... I've also recently switched to using a D-Link router as a wireless hub, which creates its own wireless/n network. Unfortunately this didn't solve my problems, as the new n network can be joined, but there's no connectivity to the internet. I know that's not much info to help others solve my problem, so please let me know of what else I can provide to make this a better question -- and possibly help others facing similar trouble. lsusb reports that I'm using Realtek Semiconductor Corp. RTL8188SU 802.11n WLAN Adapter

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  • Wireless not working with an Atheros AR9285

    - by Neeraj
    I recently installed Ubuntu 12.04 and found my wireless card is not detected by OS. I tired to detect it by network manager but still it is not get output of the required command: toor@Linux:~$ sudo lshw -class network *-network description: Ethernet interface product: AR8131 Gigabit Ethernet vendor: Atheros Communications Inc. physical id: 0 bus info: pci@0000:03:00.0 logical name: eth0 version: c0 serial: f0:de:f1:9e:22:4d size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress vpd bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=atl1c driverversion=1.0.1.0-NAPI duplex=full firmware=N/A ip=124.123.227.84 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s resources: irq:44 memory:f2400000-f243ffff ioport:2000(size=128) *-network UNCLAIMED description: Network controller product: AR9285 Wireless Network Adapter (PCI-Express) vendor: Atheros Communications Inc. physical id: 0 bus info: pci@0000:04:00.0 version: 01 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: latency=0 resources: memory:f2500000-f250ffff and toor@Linux:~$ rfkill list all 0: ideapad_wlan: Wireless LAN Soft blocked: yes Hard blocked: no 1: ideapad_bluetooth: Bluetooth Soft blocked: yes Hard blocked: no Please let me know what more info is required to resolve it.

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  • Create personal wireless network on laptop

    - by TechGuru
    I have a WiFi Network, now I have connected my laptop to the WiFi Network. And it is working fine I'm able to access the internet via WiFi. But I want to create other network on my laptop so that I can connect my mobile phone to the my laptop network. Means, my laptop is already connected to WiFi network (xyz). Now I want to create one wireless network on my laptop. So that I can connect my mobile phone to laptop network and access the internet on mobile. But I don't want to lost my `laptop and WiFi connection that is already connected. I tried to create the wireless network on my laptop, but when I created my personal wireless network I lost my wifi-laptop connection. I don't know it is possible or not.

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  • Dell wireless not working after upgrade

    - by Omer Saeed
    So, the short version of my sad story is that I tried upgrade Ubuntu to 12.04 and wireless driver has stopped working. I have tried all the solutions but nothing seem to be working. When I try to install my wireless from "Additional Drivers" Its says: Sorry, installation of this driver failed. Please have a look at the log file for details: /var/log/jockey.log The lspci command gives me the following info about wireless: 0c:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01) I have tried removing bcm drivers and reinstalling, but nothing seems to be working. rfkill is good too.

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  • Wireless network unstable and often WPA2 protected networks just don't work

    - by Pedro
    I have an issue with my wireless network,so that the connection is working for only a few minutes, after which my browser no longer is able to load pages, even if the wireless is still active/connected. Furthermore, most of the time WPA2-personal protected networks don't work, (yesterday was the first time it worked - for a few minutes). By "don't work" I mean that it seems to successfully connect, but the browser can't load pages. I am running Ubuntu 10.10 32bit, and my wireless card is a RaLink rt3090. No changes have been done to any settings since Ubuntu was installed - networking began working on its own after the installation - but as described in first paragraph not very well.

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  • Kubuntu 12.04 Won't let me search for wireless network

    - by Bora George
    Hello I'm running a brand new Kubuntu 12.04 single boot on my laptop, this is the first time I tried connecting to a wireless network. I tried using the network manager app allready on the task bar, but it doesn't let me tick the column to search for wireless networks, i.e. it will untick it automaticaly, it's dissabled by the software or the hardware, but I doubt it. I've tried searching the other questions on this site, and I can't see anything which helps with my problem. I know my wireless card is a Atheros AR9285, I don't think I installed any firmware for it, I'm sorry I can't offer more info but I'm completely new to networking and all that I have for the network to connect to are it's name and password of course.

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  • Slow wireless about 1/3 bandwidth of wired from cable modem

    - by Rhino
    HP DV6000 Wireless G Broadcom Netgear WNDR3400 router properly configured. Windows laptops using wireless G and N are considerably faster than mine. 12.04 LTS, all restricted drivers and all up to date. 50Mbps wired and 9-21 Mbps wireless on Ubuntu. 00:14.0 Bridge [0680]: NVIDIA Corporation MCP51 Ethernet Controller [10de:0269] (rev a3) Subsystem: Hewlett-Packard Company Presario V6133CL [103c:30b7] Kernel driver in use: forcedeth 03:00.0 Network controller [0280]: Broadcom Corporation BCM4311 802.11a/b/g [14e4:4312] (rev 02) Subsystem: Hewlett-Packard Company Broadcom 802.11a/b/g WLAN [103c:1370] Kernel driver in use: wl

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  • Ubuntu 12.04 lts cannot build a wireless connection

    - by Jupiterr
    Hi i just got a new notebook and it came with ubuntu 12.04 lts operation system. But it can't make a wireless connection. I plugged in my Ethernet cable and i can reach the Internet with it but I need wireless connection so much. This is the first time I'm using ubuntu so i'm really confused. I can see wireless networks (including mine) but i cannot use them. It seems like it's establishing a connection but soon it gives up. Please help, I don't have much time for this and I do not have any idea about operation systems.

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  • atheros wireless ar9285 driver

    - by nikola
    I have been having problems with wireless on Ubuntu 10 and above, Mint 11 and above. The problem is in the driver for the wireless... I can see that there is no driver installed and yet it works but reduced a lot, for example: on windows 7 ultimate 100% on distance of 1 meter (currently running) Mint Cinnamon 15 on same distance 70% when it goes under the 40 % it simply disconnects and than takes a lot of time to connect again I am new to Linux and I don't know anything about programming, yet I love the interface and look of the OS but don't want to reject it for couple of problems. There is, however, a problem with brightness control on laptop, it shows the notification and slider but with no effect The question is: Can somebody explain to me where to download and how to install the ar9285 driver for atheros wireless card laptop acer emachines eme529? or can someone explain this to me only for the LINUX MINT 15 http://www.jrhenkelmann.net/index.php?option=com_content&task=view&id=34 because the synaptic's interface is different than of mint 15 I KNOW this is Ubuntu community but the problems persist in all Linux versions

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  • How to reset wireless card settings

    - by Nissan911
    Yesterday i was playing around of the wireless settings, and set up a tftp server. Today, i found the wireless icon does not show up on the panel anymore.. monitor and bluetooth are still there... I did: ifconfig -a, and it shows: etho0 link encap:ethernet, and it has: HWaddress inet6 addresss. RXbytes 0 TX bytes: 0, but it does not even have a ip4 address, nor a mask. The other one is: l0 link encap: local loopback inet addr 127.0.0.1. mask 2550 0 0 Can anyone help me how to reset the settings for my wireless connection? Thanks

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  • Wireless not functional

    - by Michael Berkenblit
    I am a complete newcomer to Ubuntu. Today I installed Ubuntu 12.04 onto an 3 or 4 year old laptop - an HP DV2221. Install went fine, except that I can't get the wireless card to operate. I see that there are drivers installed (Broadcom STA wireless) and it says they are activated, but the wireless light on the body of the computer is lit as orange, when it should be blue, and if I disconnect the Ethernet wire, there is no ability to get onto Firefox. I've looked at some of the similar questions on this site, as well as Googling the issue - mostly, I guess I don't understand how to navigate or do some of the fixes recommended - I'm fairly adept technologically around Windows, but know zilch about Linux and how to perform some of the fixes - so, if possible, please tell me how I get to the menus needed to rectify the situation.

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  • Need a few reboots to connect to wireless

    - by Debajyoti Nandi
    I am running xubuntu 12.10 on my msi wind U100 netbook. I have a problem with the wireless connection. Whether the wireless connects automatically to a known wifi hotspot (both at home and starbucks) is temperamental. Sometimes I need to reboot one or more times to get it connected. Otherwise, it tries and keep asking me to enter the password (which is saved and when it works it does, so the problem is not with the password). Every time my computer awakes up from sleep the same problem. I have to do a reboot to connect to wireless. I searched everywhere but found no solution. I would greatly appreciate if someone has any solution. I will gladly share the hardware/software or config info, if asked, but I don't know exactly what to share and where to find them. Thanks you for any help.

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  • Wireless/Bluetooth problems on t43p

    - by user75965
    I have been struggling to get my wireless mini pcmcia card recognised by 12.04. It suddenly stopped, mid session. I have taken it out and replaced with a couple of spares with slightly different serial numbers. One had no joy - 'unauathorised'. The other worked briefly for thunderbird but not firefox, it seemed. The network controller reads like this: 0b:02.0 Network controller: Intel Corporation PRO/Wireless 2200BG [Calexico2] Network Connection (rev 05) I have ordered a replacement from ebay, and hope I got the right one - used the the FRU number from the one that stopped working. But I have ALWAYS had no joy with my Thinkpad t43p Bluetooth and Ubuntu ( 12.04, and even 11.04 and 11.10, if I remember rightly). Do you think the Bluetooth problem will solve with a new mini pcmcia? Surely not, as it has never worked, whereas Wireless worked until a couple of weeks ago...

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  • Wireless doesn't connect in Ubuntu 10.04 Lxde

    - by David
    Problem I have a Dell mini 9, and the wireless has worked without trouble in Ubuntu and Xubuntu versions 8.04 and 10.04. However, after installing lxde, the wireless doesnt connect. Network manager recognizes the local networks, and will say that it is connected, but ifconfig does not confirm the connection or the existance of a wlan0. I have another Ubuntu 10.04 notebook that works fine. My wireless device is Broadcom BCM4312 802.11b/g What I have tried I have tried to remove and install network-mananager and inxi but neither work, and sudo modprobe wl returns WARNING: All config files need .conf: /etc/modprobe.d/blacklist, it will be ignored in a future release.

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  • If I enable/disable my wireless device, my computer will panic

    - by Yinyanghu
    Now, I use Debian 6.0.6 instead of Fedora 16/17. But I still sustain the problem of my wireless problem. If I enable/disable my laptop wireless device or my usb wifi adaptor, my laptop will panic. It seems like all the processes stop at that time and I have to restart my laptop directly. P.S. I think I installed the drivers correctly and the linux kernel may have some bugs. For example, when I unplug my usb wifi adaptor or I use this command, ifdown wlan0 I encounter this problem. Wireless Device: PCI: 03:00.0 Network controller: Broadcom Corporation BCM43225 802.11b/g/n (rev 01) USB: Bus 002 Device 005: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN

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  • Can't connect to wireless without typing sudo modprobe b43 in terminal

    - by user90889
    I just upgraded to 12.04 on an old ACER Travelmate 5320 using Broadcom 4311. I wasn't able to connect to the internet through the wireless for a few days. It didn't even display wireless networks. I was finally able to make it work by following the instructions found here: http://linuxwireless.org/en/users/Drivers/b43#supported However, each time I log on to the computer I have to go to the terminal and type sudo modprobe b43 to make the wireless work. Is there somehow I can avoid this? I have used Ubuntu for many years but always relied on other people to help me with the technical stuff. The terminal is alien to me so I literally follow online forum instructions without knowing what I'm doing. Also, I tried many many things before I managed to make it work. So I'm worried I may have installed something that now conflicts with whatever the sudo modprobe b43 does. Thank you

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  • No wireless after resuming from suspend?

    - by lapor
    When I resume my computer from suspend it doesn't want to connect to any wireless connection. It looks like it is connecting, but after a while it asks me to retype a password for wireless connection. It connect after I restart it. I am using Toshiba Satellite A210 and Ubuntu 10.10 (I have the same problem with 10.04 and 11.04 beta2. 14:00.0 Ethernet controller: Atheros Communications Inc. AR5001 Wireless Network Adapter (rev 01) Subsystem: Askey Computer Corp. Device 7128 Flags: bus master, fast devsel, latency 0, IRQ 19 Memory at cfcf0000 (64-bit, non-prefetchable) [size=64K] Capabilities: <access denied> Kernel driver in use: ath5k Kernel modules: ath5k Should I file a bug?

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  • Ubuntu 12.04 on Vm Player showing Wired Network Instead of Wireless Network

    - by Fak365
    I am new to Ubuntu, recently I installed ubuntu 12.04 in Vm Player (Virtual Machine) on my Dell laptop having windows 7 ultimate 32 bit for just to check the security of my wireless network and want to crack the WiFi (WPA-PSK) password but in ubuntu it does not show the wireless network it shows the 2 arrow sign as i have not connect the ethernet cable to my laptop and connected through WiFi on my main OS (windows 7) but it shows the wired network and internet is working but it does not show wifi connection. On windows 7 WiFi is connected and showing the WiFi connection and working correctly.But my main motive is to crack the WiFi password as it can't detect WiFi network so what to do? Please Help.!!thanks My Laptop Specification : Laptop : Dell Latitude D620 OS : Windows 7 Ultimate 32 bit Processor : Core Duo 2 T7200 @ 2Ghz Ram : 2 GB WiFi card : Intel Pro/Wireless 3945 ABG Virtual Machine : Vm Player V 5.0.1 If Need to Install Drivers Please Give Me Full Information how to install and which driver I should install. Thanks In Advance.

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  • wireless not working, but wired does

    - by user211762
    First of all I'm new to Ubuntu, just bought a laptop with Ubuntu yesterday. I disable wireless networking in the upper right corner, and I don't have option to enable it back. I tried a lot of things and none is seems to work: I installed Wicd network manger, and it says no wireless network found, but i assure you there are several of them as my smart tv can detect them. when I type rfkill list, I get this: 0: dell-wifi: Wireless LAN Soft blocked: no Hard blocked: no when I type ifconfig wlan0, I get this: wlan0: error fetching interface information: Device not found

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  • Manually re-enable wireless and bluetooth

    - by tacozmeister
    So, today, I decided to turn off bluetooth to save battery power. When I did so, it did everything like normal. Whatever. But whenever I want to re-enable Wifi and Bluetooth, it just has "Enable Wireless" and "Enable bluetooth" grayed out in the respective things on the top-right of the desktop. I am using 12.04 Precise Pangolin on a Dell laptop that has never had wireless problems before. Clicking the grayed-out part does nothing. Re-logging and restarting has no effect, and I'm on an account that has full administrative permission. My attempts: ~$ sudo dmesg | grep wlan0 [19.960211] ADDRCONF(NETDEV_UP): wlan0: link is not ready . ~$ sudo dmesg | grep blue [[nothing]] What do I do to manually re-enable wireless and bluetooth?

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  • Router to WIFI Client to Router (New solution for distance when repeater doesnt help)

    - by Kangarooo
    Ethernet to TL-WR340G with WIFI enabled Using TL-WA500 tried repeater mode which was not good enough and had password problems (could not connect if using either ASCII or Normal password in one way then in repeater worked other way) and also could not forward (repeat) WPA/WPA2 security. So since this repeater can also be as client, I made it as client and used another router (TL-WR740N) to get from wire connection from that client and all was working for a little bit. Every machine is set up to be auto DHCP. 1st when setting up client mode I found it working after doing reset. Then after some tens of minutes internet stopped working. When I removed WiFi client then all went back to normal. Where is the problem and how to make this work? Ethernet- TL-WR340G(AutoDHCP) ==> wifi ==> TL-WA500 TL-WA500 wifi client mode(AutoDHCP) ==> wire ==> TL-WR740N TL-WR740N router mode (AutoDHCP) ==> My Computer In other words: TL-WR340G ) ) ) ) TL-WA500 ===== TL-WR740N ==== PC1 ) ) WiFi === Wire

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