DTMF and Symmetric NAT

[Grahame]

Having recently experienced some voice quality problems with a couple of Providers, I followed the post " How to Improve Your Voice Quality ".

I changed my settings as per the post i.e symmetric NAT NO, Optimise Audio YES and indeed call quality did improve.

However, I now find DTMF is not being recognised if I make calls to numbers which require " Press 1 for Sales etc ".

I have changed back to symmetric NAT Yes and Optimise Audio No and all works perfectly.

Why would the NAT setting block DTMF ? Any help gratefully received.

Best regards

Grahame