In effect, yes. The phones will still have DHCP and DNS from the main router but they send their SIP calls to SARK (which is all that matters). SARK knows where its own upstream server is so it sends the SIP over that. Obviously, you shouldn't have SARK giving DHCP in competition with the existing DHCP server. The only other thing to watch is if you are provisioning the phones fom SARK with TFTP then you will have to figure out a way of telling the phones where the TFTP server is. In SARK DHCP server we send option 66 to do this. If your existing DHCP server supports option 66 then use that otherwise you may have to hardcode each phone to tell it where the TFTP server is. If you are fortunate enough to have SNOM or Yealink phones then you can just turn on SIP Multicast provisioning in SARK and that problem disappears.
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