[cisco-voip] ATA190

[Ryan Huff]

Forgive my digressions and tangents; I’ve been reading SIP debugs for a large swath of the day; I’m in that “techsplaining” mode. After a re-read, I do hope you know I wasn’t implying you might know that already 😊.

I understand now, the humor in what you’re saying 😊. I could imagine that would flip the I3E on their heads … all the sudden, Belkin OUIs start showing up in ARP tables coming from Cisco ATAs, lol.

Thanks,

Ryan

________________________________
From: Anthony Holloway <avholloway+cisco-voip at gmail.com>
Sent: Tuesday, May 22, 2018 2:45:59 PM
To: Ryan Huff
Cc: Jon Fox; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] ATA190

Haha, that was way more than I was suggesting.  I was just thinking like, what if the second vendor was like Selsius, and a tip of the hat.  An easter egg of sorts.

On Tue, May 22, 2018 at 12:46 PM Ryan Huff <ryanhuff at outlook.com<mailto:ryanhuff at outlook.com>> wrote:
As I recall, from the last time I had the occasion to deal with an ATA; I think port 1 uses the device’s media access code, and is what ultimately gets resolved into the ARP table. From a network perspective, I don’t think any thing/scanner could ever “see” a non-cisco device on the network due to this method (which is why I believe Cisco may have chose this behavior), short of what you’ve done here by manually looking up the ‘spoofed’ OUI that is reported by RIS in the CCM GUI.

I believe, if I’m not mistaken, the ATA uses software magic to register/communicate port 2 with a shifted/appended MAC address to “play nice” with CCM’s unique device name requirement. I could be entirely wrong though; I’m basing my statements off of dated experience (I haven’t used an ATA in close to a year) and I don’t have an ATA at the ready to test with.

Thanks,

Ryan
From: Anthony Holloway<mailto:avholloway+cisco-voip at gmail.com>
Sent: Tuesday, May 22, 2018 12:54 PM
To: Ryan Huff<mailto:ryanhuff at outlook.com>
Cc: Jon Fox<mailto:jonfoxipt at gmail.com>; cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: Re: [cisco-voip] ATA190

Aren't the first few values of a MAC tied to the vendor?  If so, does this trick make it look like the second port is a different vendor product?  And if so, it would be funny if it was a competitor.

Ah, but no such luck today.

[cid:ii_jhhx33e01_16388c3b26b144f0]

Source: https://macvendors.com/

On Tue, May 22, 2018 at 4:30 AM, Ryan Huff <ryanhuff at outlook.com<mailto:ryanhuff at outlook.com>> wrote:
Yes, that is correct.

The ports are differentiated by the device name. However, the ports themselves are registered to CCM and communicate on the network through a single network interface on the ATA.

The second port in the ATA will have the first two characters striped from the beginning of the MAC address and a “01” appended at the end of the MAC address (shown in the device name of the two ports).

Essentially, the ATA is a mini, purpose built media conversion switch. A lot going on under the hood of those silly little things when you think about it :).

Thanks,

Ryan

> On May 22, 2018, at 04:57, Jon Fox <jonfoxipt at gmail.com<mailto:jonfoxipt at gmail.com>> wrote:
>
> Hello All
>
> Trying to troubleshoot an issue with a Cisco ATA - CUCM 10.5.2SU3
>
> I've not had to touch these for some time, so cannot remember if its natural behaviour for Port 1 and Port 2 registering with the same IP address? Is that standard? - Screenshot attached.
>
> <image.png>
>
>
> Many thanks
> Jon
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