id summary reporter owner description type status component version resolution keywords cc guest host 13899 """VboxNetNat.exe"" Random crashes -> fixed in 6.0.4" qidizi "host OS:window 7; host some software:avast!; noteBook:lenovo k27,intel I3,RAM 8G,ssd 128G; host network:LAN,or LAN wifi; guest OS:centos 7; guest network:NAT network,forwarding port(tcp127.0.0.1:22 => 10.0.2.5:22,tcp127.0.0.1:80=>10.0.2.5:80;tcp127.0.0.1:3306 => 10.0.2.5:3306),interface:Intel Pro/1000 MT server (82545EM) mixed mode is disabled; vm virtualbox VER:4.3.23-98520/4.3.22(test both ) when testing,only this guest OS is runing! my email is :qidizi&qq.com If you are using a NAT(not NAT network), this problem will become more serious, see the following https://www.centos.org/forums/viewtopic.php?f=50&t=51112 If you use the ""bridging model"", this problem would not have arisen; Possible causes:postfix(http://www.postfix.org,Install on CentOS systems) is runing,and A large number of mail is being delivered;and the browser on the host(window on ""k27""), constantly refresh a PHP page,the ""nginx/php"" on Centos;then ""VboxNetNat.exe"" Random crashes,But I cannot determine what operation caused crash; " defect closed network/NAT VirtualBox 4.3.22 fixed NAT TechSalesDude Linux Windows