Hi , need a help to configure asterik.

1] i have setup asterisk 1.8 with centos 6.2 machine
2] i have place the asterisk machine in hq, its connect to lan switch and there is H.323 voip gateway hardware device in lan and two unit anolog phone connect to that H.323 voip gateway hardware.
3] I have setup h323 voip gateway in the branches and now able to ping each other.
4] do i need to setup gnugk/gatekeeper on the centos 6.2 machine ?

kindly assitance step by step

Thank you very much.