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Cisco CallManager calls to FXO MGCP Gateway fails with the "510 protocol error" error message


Core Issue

Calls to MGCP FXO Gateway return the 510 protocol error message if the Cisco CallManager does not send the dialed digits to the gateway.

The CRCX message from Cisco CallManager to the gateway has no dialed digits so the gateway should take the port off hook and go for it. But, instead it sends the error message to the Cisco CallManager.

With a Cisco CallManager version, this issue can happen if the route pattern is configured with discard digit for all the called party numbers. and when Cisco CallManager sends the CRCX messages with S: H/Sup and without digits (x,y,z) as an option.


The issue is documented in Cisco bug ID CSCsi19351.

The issue is fixed in these versions:

  • 4.2(3)SR02

  • 6.0(0.9901.198)

  • 5.1(1.3106.002)

  • 4.3(1.40)

  • 5.1(1.9131.047)

  • 5.0(4.2137.001)

  • 4.2(3)ES25

  • 4.3(1)ES04.1


Do not discard the dialed digits on the Cisco CallManager.

Open a case with Cisco Technical Support with the TAC Service Request Tool in order to obtain an appropriate Engineering Special patch

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