Hi, My name is Eric Moyers. I am a Network Support Engineer in the Cisco Small Business Support Center. Thank you for using the Cisco Community Post Forums.
There is no set fallback Internet speed. As congestion and interference increases speed decreases. It does not have a set interval.
Please let me know if you have any other questions.
Thanks
Eric Moyers
Cisco Network Support Engineer
CCNA, CCNA-Wireless
1-866-606-1866