DDNS Troubleshooting

[rancid-lemon]

Hi All,
My goal is to set up DDNS using my own domain through no-ip service provider. Right now I'm having difficulty in getting the client working in pfsense.

I started troubleshooting, and almost straight away I came across something I don't understand.

Essentially, my WAN inferface IP doesn't appear to be my external IP.

If I explain a little more could anyone enlighten me / point me in the right direction?

Essentially I have this:
Current WAN IP on pfsense box:
86.31.X.X

Current WAN IP reported by a 'whats my IP' website:
86.31.Y.Y

I suspect this is something to do with my ISP (Virgin Media in the UK). I am using the provided hub in modem mode straight into the WAN on my pfSense box.