While the counterfeit devices work identically to the genuine ones, experience has shown that they tend to fail much quicker than the genuine devices, most of the time within the first few weeks or months of use. The typical behaviour of a failed device is that it doesn't boot, doesn't respond to web access and phone commands and the power LED stays red (orange in the case of PAP2T). Most of these are coming from sellers in China / Hong Kong but some local sellers also import them in bulk and retail them locally.
This page (thanks to voipfan.net) attempts to help you determine if your PAP2(T) is genuine or counterfeit.
I must mention that since this page was published, the manufacturers of counterfeit ATAs have been doing a better job at making them look more closer to the genuine ones, so it's getting harder to spot them. That's why even if your ATA passes all the tests here, I still can't guarantee it's genuine.
1. Appearance of the front labels. The labels on the front and back use a combination of black and blue colors. For both PAP2 and PAP2T, the front label should have the Linksys logo on blue background and the Cisco logo on the black side for PAP2T or the words "Phone Adapter with 2 ports for Voice-over-IP" for PAP2. Also the PAP2 has the Cisco logo printed on the front panel, on the silver side. The photo below is of genuine ATAs.
The fake ATAs may have the wrong inscriptions for the model, or the label may be be printed in the wrong shade of blue. In the samples of counterfeit adapters below, the one on the left (PAP2) has the blue part of the label faded, while the one on the right uses a shade of blue that's too dark, has the wrong inscription for PAP2T and the Linksys logo is missing the ® symbol:
2. Serial number and MAC address from the label on the back. The serial number and MAC address should be printed in barcode as well as readable characters, directly on the back label, as in the first picture below. If the MAC address and SN are printed on an additional sticker placed on top of the label, as in the middle picture, or if only the barcode is printed, like the picture on the right, the ATA is a counterfeit.
3. Appearance of the back labels. The back labels are again a combination of black and blue. For PAP2 (left side in the photo below), the blue part is shorter and all the writing and symbols are on the black side. For PAP2T (right side), the Linksys and Cisco logos and the model number are inside the blue part, the rest is black (I did not have a photo of a genuine PAP2T I would trust, so I used a SPA2102 photo, but the label design is the same).
Here you will have to pay attention to the fonts used for printing the model number as well as the MAC address and serial number. For PAP2T, all the fonts are a little narrow. For PAP2, the font for the MAC address and serial number is a little wider. As far as the model, the words "Model No." should be printed black on white background, while the model should be with white writing on black background for PAP2, blue for PAP2T.
(click on the image for a higher resolution)
The photo below is of a fake PAP2T that breaks several of these guidelines: wrong fonts and font sizes for everything, wrong shade of blue, PAP2T-NA written with reverse colors.
4. Vertical stand. The original PAP2 had a recessed area with 2 holes on the bottom where a plate could be attached to make the ATA stand vertically (like the left photo below). This has been removed from PAP2T which should look like the photo on the right.
The ATA on the left is counterfeit because it claims it's a PAP2T but has the feature described here.
5. Warranty stickers. The genuine PAP2 and PAP2T have no warranty stickers applied by the manufacturer anywhere on the outside case. The ATA below came with stickers like that and is counterfeit.
6. MAC address check. Take the first 6 digits of the MAC address (002369 in the sample above), enter them in the next field and click Search.
In the page that opens check the value for Vendor. It should say Cisco, Linksys or Sipura. If it shows a different company, the ATA is a counterfeit.
7. Verify if the MAC address and Serial number printed on the label match the ones shown in the adapter's web configuration page. With the adapter connected to your network and a phone connected to the adapter, pick up the phone and dial ****110#.
The adapter will read back (with voice) its IP address. Open a browser and enter that IP address. This will bring up the Info page of the ATA, similar to the one below.
Compare the MAC and Serial number printed on the back of the unit with the ones from the Info page. If they don't match, the adapter is counterfeit.
8. Check the appearance of the packaging. There are three types of boxes (pictured below) that Linksys ATAs are shipped in. The design on the left has been used by Linksys only for the original PAP2 adapters. If a PAP2T comes in a box like that, it is most likely a fake. An original PAP2T may come in either one of the boxes depicted on the right (the top one is the retail box, while the bottom one is typical for ATAs sold through a VoIP company).
9. Appearance of the power adapter. There are 3 types of power adapters I've seen shipped with Linksys ATAs. The two on the left photo below are typical for PAP2 and PAP2T while the one on the right is a new design used with newer models like SPA112.
The adapters below are both from counterfeit PAP2Ts. Note that the design of the labels doesn't quite match the genuine ones, also they are poorly attached.
On the prongs side, there must be a detachable clip like in the left side of the photo below. The adapter on the right side, without a detachable clip, came with a counterfeit ATA. Another small detail I've noticed on some power adapters that came with counterfeit PAP2Ts was that the tip of the power plug was yellow, rather than black as it should be on the genuine PAP2Ts.