Questions tagged [wireless]

For questions about wireless networking (802.11), including any licensed or unlicensed RF medium used to provide point-to-point or point-to-multipoint network links.

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22
votes
5answers
85k views

Is it safe to use any wifi channel in the 2.4GHz band?

It seems that everything I read about wifi says there are only three usable channels in the 2.4 GHz band; however, there are eleven 2.4Ghz wifi channels allowed in the US. If everyone is using 1, 6 ...
10
votes
1answer
10k views

Four layer-2 addresses in 802.11 frame header

I am new to wireless LAN. I see that it has 4 addresses in the frame header. In case of a Wired Ethernet, there are only 2 mac addresses, the source and the destination (which is essentially the ...
19
votes
4answers
24k views

LAP ignores DHCP Option 43 and uses CAPWAP UDP broadcasts

Background I am trying to redeploy Cisco 1242 LAPs on new Cat4507R+E switches, which means the IP address of the WLC is changing for that LAP. For some reason, I have to configure ip helper-addresses ...
18
votes
4answers
23k views

Why does WLAN use Collision Avoidance and not Collison detection?

I am searching for this answer for quite some time now. Why there is CSMA/CD in LAN but CSMA/CA in WLAN? The best explanation I could find is "due to extreme ratio in transmitting and receiving power,...
8
votes
1answer
2k views

Staging Many Lightweight Cisco AP's for Deployment

My organization is soon going to be deploying approximately 600 new Cisco 2602i access points in a CAPWAP deployment with several 5508 controllers. This is an infrastructure refresh; currently we ...
14
votes
4answers
1k views

Is a wireless only network (for end users) a viable option?

We are constructing a new building, and our CIO is pushing for a solution where he doesn't have to spend the money on copper runs to all the user stations and wants to use wireless only for this ...
6
votes
1answer
513 views

Why do we have authentication before association in 802.11

Why does client authenticate before associating with the AP. What does open system authentication even achieve. I fail get an accurate reason from my web searches. Best reason I do get is unlike wired ...
39
votes
11answers
36k views

How do you prevent rogue wireless access points on a network?

Depending on what type of traffic is going over the network, it's often not feasible that an employee brings a wireless router and sets it up into your network. This is because often, they are not or ...
17
votes
2answers
57k views

How does a WiFi range extender work?

I have a WiFi base station, and a WiFi range extender. Both of them have the same SSID. When a device connects to that SSID, what exactly happens? How does the device know that base station and range ...
9
votes
3answers
1k views

VM on a client connected to a Cisco 1262 unable to DHCP (but IPv6 works fine)

I recently replaced wireless at a site from the internal AP on an 877-WM with a (standalone) 1262 running 15.2(2)JB. I've configured the AP pretty much the same as I always do for Cisco AP's for ...
10
votes
4answers
31k views

converting AP from CAPWAP to autonomous - BVI1 interface gets reverted back to DHCP

Has anyone ever gotten this message in the middle of converting a CAPWAP access point from CAPWAP to autonomous? *Mar 1 00:47:59.399: %CAPWAP-3-STATIC_TO_DHCP_IP: Could not discover WLC using static ...
9
votes
2answers
24k views

Can I truly multicast over WIFI?

Am streaming UDP over wifi (5ghz) - approx 1.5k/packet... trying to stream to ~10 devices simultaneously, with extremely low latency.. As I understand Wifi, it can never true multicast, as each ...
6
votes
2answers
6k views

Why Don’t Probe Requests for Specific SSIDs include BSSIDs

I'm looking at WLAN traffic captured from wireshark on monitor mode and notice that out of the 67,000 probe requests, 99.08% have the destination set to FF:FF:FF:FF:FF:FF (Broadcast). The thing is, ...
13
votes
3answers
32k views

Mac-flap due to roaming clients on wireless

We are running an Aerohove wireless network (controller-less).. I occasionally get mac-flaps within the VLAN tied to a SSID. I know this is coming from a roaming client.. The problem is that the ...
10
votes
3answers
4k views

Why does my UDP Broadcast wireless communication is capped at 1MBs?

I am trying to implement Network Coding over a meshed network. Therefore I need to send packets to several destinations, this is way I am using Broadcast packets. But I can not understand why this is ...
4
votes
2answers
2k views

Is 802.11 bitrate symmetric?

I was wondering when a device spec says that it supports WiFi bitrate of 300 Mbps, is this rate symmetric, i.e. is it the same rate in transmit (device to access point) and in receive (access point to ...
2
votes
1answer
2k views

Relation between Ethernet and 802.11 headers

I would like to ask about the relation between 802.11 and Ethernet L2 Link layer. Are they dependent of each other? Or can they be seen as independent L2 link layers (with only similarities in ...
7
votes
2answers
501 views

How is the Groupwise Transient Key used in WiFi networks?

In Wifi WPA, I understand that during association, a 802.11 client and AP negotiate a Pairwise Transient Key (PTK), using which the Groupwise Transient Key(GTK) is provided to the station. I ...
6
votes
2answers
91 views

How the packet is routed between two host from same sub-net and associated with same AP?

Given host 'A' and 'B' have IP 10.10.0.5 and 10.10.0.8 respectively, the sub-net mask for both are 255.255.255.0, both 'A' and 'B' are associated and connected to the same AP, and the AP is connected ...
5
votes
2answers
5k views

Do wireless routers on the same channel share frequencies actively or simply collide?

In the scenario of 802.11n 2.4GHz routers, and assuming a very simplified example of only channels 6 and 11: Us in Building A: router on channel 6 -- next door -- Building B: router on channel 6 -...
4
votes
2answers
4k views

AODV sequence numbers and loop prevention

I am learning about the AODV (ad-hoc on-demand distance vector) protocol. I saw a "sequence number" with a value like "A 46"; however, I don't understand why incrementing this sequence number can ...
3
votes
2answers
838 views

Does WiFi broadcast traffic from a station go through the access point?

Let's say I've got two devices connected to my Access Point, a laptop and a tablet. If the laptop sends unicast traffic to the tablet, I understand that it must go through the AP. However, how is ...
3
votes
1answer
399 views

What is the IS-41 location registration process?

I am unsure what the IS-41 location registration process is. Could someone please explain this?
2
votes
2answers
115 views

Wireless LAN Controller

I have a Cisco 2500 series WLC, and a 1700 series LWAP. In this case, what provides the AP the DHCP IP address, my router or the WLC?? There is already a PoE port in the WLC, yet when I connect my ...
2
votes
2answers
310 views

Is it really necessary for APs to constantly send beacon frames (always be in “discovery mode”)?

Why do wireless APs constantly transmit (e.g., with a beacon interval of 10×/sec.), even when no devices are connected to them? Doesn't that just cause needless RFI? Is it really necessary to ...
1
vote
2answers
71 views

Airtime efficiency

How is airtime efficiency measured? How does one increase it, decrease power consumption, and minimize the amount of RF transmitted? cf. these comments
1
vote
1answer
2k views

Capturing and sending 802.11 Frames/Packets [closed]

is there any program that enables me to capture 802.11 frames/packets in my environment (like wireshark when my interface is put in monitor mode), then sends the captured data over TCP/IP to broadcast ...
0
votes
2answers
80 views

Packets for Internet Connection [closed]

Consider the following scenario: AP is an access point with internet connectivity and in idle state (ie: no node is connected to it) N is a node that wants to establish an internet connection ...