I have a problem of Very High proportion of CRC error when I connect a Cisco 7940 phone to my Meraki MS355-24, immediately the port is blocked.
I changed several patch cords, but it doesn't work properly. Does anyone have any idea about this error? how can i solve it?
Solved! Go to Solution.
I plugged the same phone into another port, but I throttled the connection to 100 mb and I see this now:
UDLD had detected a TX/RX loop.
After that, it disconnects the port and sends me the message:
Very high proportion of CRC errors on port 12
Configure the port to 100 Mbit because if I leave it automatic it does not connect. In addition, the phone does not turn on even though PoE is enabled.
I have a meraki MR57 AP connected, and it works correctly, but I connect the phone and it doesn't want to turn on.
Cisco 7940's only support Cisco's proprietary PoE implementation, which is not available on Meraki switches. Therefore it's expected that the phone will not power up via PoE.
As for your other comment with CRC's and the phone only communicating when brought down to 100Mbps - that smells very much like a layer 1 problem somewhere along the line. Replace the cable (and SFP if applicable).
Meraki begun as a separate company and was acquired by Cisco. Therefore they don't typically use Cisco proprietary features, but opt for industry standards.
One example of this that comes to mind is Spanning Tree.
To be honest, I'm not even sure whether Cisco still uses their proprietary PoE implementation over the standard these days (haven't deployed a Cisco IP Phone in years).
If the phone has an external power supply, it won't require PoE and therefore it will resolve your issue of the phone not powering up.
I'm not confident it will solve all of your CRC issues though.
The 7940 is very very very old. I think @Brash is right.
I would look to a solution to replace the 7940s. It's amazing they are still running!