RIP problem

Hi,

On my systems logs I get

---=== RIPv2 RESPONSE ===---
prefix=10.31.255.128/27 metric=2 nexthop=0.0.0.0 tag=0
184 bytes received from 10.64.0.1:520
ignoring RIP message: unknown sender

I don’t know why this RIP message is getting ignored as 10.64.0.1 is the gateway I need to access another network. How could I solve or futher debug this issue?