[root@bind ~]# yum update
Loaded plugins: refresh-packagekit, rhnplugin
This system is not registered with RHN.
RHN support will be disabled.
ftp://192.168.85.1/pub/repo/repodata/repomd.xml: [Errno 14] PYCURL ERROR 7 - ""
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: repo. Please verify its path and try again
[root@bind ~]# yum clean all
Loaded plugins: refresh-packagekit, rhnplugin
Cleaning up Everything

We get this error while installing / updating packages or Updating via yum configured to use repositories on a remote ftp server and iptables (firewall) restricting clients from accessing data on the ftp  server.

So we need to open iptables so that clients can access the packages and data on th e ftp    server.

 CLICK HERE TO SEE HOW TO OPEN THE IPTABLES (FIREWALL) ON FTP SERVER. 

 Another Hidden Reason

Firewall permissions for FTP is the first thing every one catch and easily allow iptables for ftp clients. But some times till you get the same error, that is proxy settings in your /etc/yum.conf file. Usually we add proxy server ip in the yum.conf file if you have proxy server in your network  or your linux machine can not connect to online repo's like epel, through proxy server.

First of all check yum configuration with below command

[root@bind ~]# yum-config-manager
======================================================== repo: repo =========================================================
[repo]
bandwidth =
baseurl = ftp://192.168.85.1/pub/repo/
cache =
cachedir = /var/cache/yum/x86_64/6Server/repo
cost = 1000
enabled = True
enablegroups = True
exclude =
failovermethod = priority
gpgcheck =
gpgdir = /var/cache/yum/x86_64/6Server/repo/gpgdir
gpgkey =
hdrdir = /var/cache/yum/x86_64/6Server/repo/headers
http_caching = all
includepkgs =
keepalive = True
mdpolicy = group:primary
mediaid =
metadata_expire = 21600
metalink =
mirrorlist =
mirrorlist_expire = 86400
name = repository
pkgdir = /var/cache/yum/x86_64/6Server/repo/packages
proxy = http://192.168.85.10:3128
proxy_dict = {'ftp': 'http://192.168.85.10:3128', 'http': 'http://192.168.85.10:3128', 'https': 'http://192.168.85.10:3128'}
proxy_password =
proxy_username =
repo_gpgcheck =
retries = 10
skip_if_unavailable =
sslcacert =
sslclientcert =
sslclientkey =
sslverify = True
throttle =
timeout = 30.0


just take a look at few lines from bottom. have you observerd proxy = http://192.168.85.10:3128......... which means you have mentions proxy server there and now your machine can't go through it, may be your proxy down or some thing. so make sure your proxy is wokring. if you want to install from local repo. Just uncomment the proxy line in /etc/yum.conr and try yum update.
[root@bind ~]# vim /etc/yum.conf

[main]
### proxy=http://192.168.85.10:3128
cachedir=/var/cache/yum/$basearch/$releasever
keepcache=0
debuglevel=2
logfile=/var/log/yum.log
exactarch=1

[root@bind ~]# yum update

That's it.

further reading: http://www.karlrupp.net/en/computer/nat_tutorial