Peterborough eased into the second round of the Capital One Cup with a dominant victory at Colchester.
Gabriel Zakuani headed Posh in front from Gavin McCann's cross, before Jabo Ibehre smashed home to restore parity.
But the visitors ran riot in the second half, with Tyrone Barnett heading them back ahead before Tommy Rowe unleashed a powerful strike to make it 3-1.
Posh forward Lee Tomlin scored twice to add gloss to the scoreline, curling in a fine effort before drilling home.
VIEW FROM THE DRESSING ROOM
Colchester United manager Joe Dunne told BBC Essex:
"Let's not carried away because we've been beaten 5-1 at home. What I don't want is negative feelings around the place already, I had enough of them last year.
"I'm positive about how we are going about things.
"We've taken a beating, and maybe down the season, we'll get another one. But we must stay positive. The team are going to be fine."
Colchester United 44 Walker 03 Dickson Booked 04 Okuonghae 18 Eastman 20 Wilson 02 Wright 06 Eastmond 14 Bond (Wright - 65' ) 28 Gilbey (Watt - 65' ) 09 Morrison 17 Ibehre Substitutes 01 Cousins 05 Thompson 25 Pappoe 10 Izzet 07 Watt 11 Sears 30 Wright Peterborough 01 Olejnik 02 Alcock (Little - 84' ) 03 Ntlhe 05 Zakuani 06 Bostwick 10 Tomlin 11 McCann (Payne - 82' ) 14 Rowe (Swanson - 81' ) 16 Kearns 09 Assombalonga 23 Barnett Substitutes 13 Day 08 Payne 31 Little 07 Swanson 12 Sinclair 20 Knight-Percival 28 Gordon-Hutton