If you want to install Asterisk from rpm's here how you can do this. First of all, you need to add asterisk repositories. You should add two repos files in your /etc/yum.repos.d.

[root@asterisk1]# touch /etc/yum.repos.d/rhel-{asterisk,digium}.repo

This will create rhel-asterisk.repo, and rhel-digium.repo. Open file rhel-asterisk.repo and add next:

[asterisk-current]
name=RHEL-$releasever - Asterisk - Current
baseurl=http://packages.asterisk.org/rhel/5/current/current/$basearch/
enabled=1
gpgcheck=0
#gpgkey=http://packages.asterisk.org/RPM-GPG-KEY-Digium

Save this file. Repeat this step for file rhel-digium.repo, but this file will has next content:

[digium-current]
name=RHEL-$releasever - Digium - Current
baseurl=http://packages.digium.com/rhel/5/current/$basearch/
enabled=1
gpgcheck=0
#gpgkey=http://packages.digium.com/RPM-GPG-KEY-Digium

Now you can install Asterisk on your system running next command:

[root@asterisk1~]# yum -y install asterisk16 asterisk16-configs asterisk16-voicemail dahdi-linux dahdi

You can start new service running next command:

[root@asterisk1~]# asterisk -vvvgci