Asterisk and SIP trunking, is this configuration possible?

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http://serverfault.com – I am new to asterisk and before I dive in, I just want to make sure that what I plan to do is possible/correct. My office will run an asterisk server and have both local and remote extensions. We have few people scattered around the US and want something scalable if that number increases. I have installed asterisk as a VM on VMware ESXi 5 but have not done any config. If I understand this correctly, I can get SIP Trunking service (the particular one I was looking at provides 1 DID and 5 ports) and have asterisk use that as the POTS gateway for outgoing calls. This will allow any extension (HowTos)