Cisco routers helps in accessing internet at a very fast speed. Cisco routers can works well over wired or wireless networks. There can be situations where user finds every connection is proper but still he is not able to connect to the internet. Now there can be few possible reasons for that.
Check the kind of router set up if it is according to the requirement like for home or office purpose etc.
May be there can be a problem from the ISP side so user should re check it again.
Check the wireless security mode. It is always recommended to use WPA2- Personal or WPA2- Open/ AES for better speed. WEP security may reduce the speed.
If the router firmware is outdated, then upgrade it as soon as possible.
May be the router is infected by the Moon Malware which affect the internet speed.