Assistance w/ getting text out of a file

I have a file that has 100 or so lines in this format: dn: cn=SERVERNAME1,ou=NWSERVERS,ou=SERVER03,ou=iServices,ou=MON,o=LA dn: cn=SERVERNAME2,ou=NWSERVERS,ou=SERVER03,ou=iServices,ou=MON,o=LA dn: cn=SERVERNAME3,ou=NWSERVERS,ou=SERVER03,ou=iServices,ou=MON,o=LA How can I strip out everything execpt the servername? Using either shell scripting, sed or perl? Thanks, Ryan