how to deny incoming packet with internal source ip address

Thanks. One of the router's interface is 10.10.0.20 and the router discards the packets with source ip address 10.10.0.10 from external for example. The ACL configuration in the router is 'access-list 5 permit 10.10.0.0 0.0.7.255'. I am not sure if it does the job. And, do you think if I add 'access-list 5 permit any' will make the packet through?

Thanks, John

You are right in that it probably has something to do with access-lists. Why don't you post your router's config (mask out any real IP's).

I am not clear about your configuration or what you want to achieve, but you should have something like:

access-list 5 deny 10.10.0.0 0.0.0.255 . < ...Other statements....>

access-list 5 permit any

and apply it to your incoming traffic.