could someone please tell me what the 1Mb/s traffic is that we are getting while the server is down?
It could be possible your server is under a high bw/high cpu type ddos attack rendering the cpu fully utilized so no system processes can handle requests (ie all sockets in use constantly). As such that could be the case as certain ddos can render a system useless unfortunately unless it's nullrouted or filtered at the datacenter level.
As such it may not even need a reboot but simply to have an ip be nullrouted if there is a ddos attack going on against your system. Unless they do private VLANs it could even be someone else in your subnet being attacked and that 2Mb/s could be residual switch traffic that the switch is trying to disperse basically.
In any case hope this sheds some light on what could be occurring with your server (obviously just an educated guess with this of course, it might be any number of things).
Best of luck with getting back up and running.