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My internet connection is via a fixed wireless connection using a 900MHz Motorola Canopy module. The router reports a fairly consistent 32-64Kbps of incoming traffic on the WAN port.

When I attached a PC directly to the port and run Wireshark, I get a dump showing a lot of chatter from other machines that I presume are connected to the same tower. This didn't include end-to-end traffic, but was there were a lot of ARP requests, SSDP traffic, ICMP and other network discovery type stuff.

Is this 'normal' or does it suggest a misconfiguration somewhere? As far as I can tell there is no need for my modem to be receiving any of this traffic (other than wanting to know what the names of my neighbours machines and printers are!)

Since the internet connection is slow at the best of time, having this amount of background noise seems very wasteful.

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2 Answers

A small amount of broadcast traffic is common but 32-64Kbps seems a bit high, especially as a entire Canopy 900Mhz AP only has 4-5Mbps of aggregate capacity under ideal circumstances.

From the level of broadcast traffic I would bet that your ISP has a typical small wireless ISP setup where their wireless network is one big layer 2 network and no layer 3/routing happens until their headend. Otherwise they may just have a lot of broadcast traffic on the one AP. Your ISP can limit that by enabling subscriber isolation on the AP but that can cause other problems.

A possible complication is Canopy 900Mhz is a point-to-multipoint system and in the default configuration the AP will repeat any broadcast traffic once (so you will get it twice).

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The network chatter depends on how the host has their network setup. Most networks are going to have this type of chatter unless the ISP is blocking it at the last leg router.

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My thought is that since I have a point-to-point wireless connection the wireless tower I connect to should be working as a level 3 router wrt to the traffic it sends to me. Instead it looks more like a level 2 bridge. I'm assuming my modem can't physically see traffic originating from another modem unless it is retransmitted by the tower. I can't think of a valid reason for the tower to be doing that. –  Rob Walker Mar 31 '10 at 14:24
    
I understand your confusion, but depending on the operator and budget, anything is possible. –  TonyZ Apr 1 '10 at 0:51
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