/rhel-dvd/repodata/repomd.xml: [Errno 14] PYCURL ERROR 7 - "couldn't connect to host"

hi every bady ;
i have some trouble in my redahat server i need some help to resolve this problem when i would to install some update with the yum command i obtain this error "/rhel-dvd/repodata/repomd.xml: [Errno 14] PYCURL ERROR 7 - "couldn't connect to host" "
please help thanks