Slackware 12.2 - Synchronizing Cisco time with Linux NTP server
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Public domain    
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### Backup

    cp /etc/ntp.conf{,.bak}

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### /etc/ntp.conf 

    # Upstream time servers
    server 0.pool.ntp.org
    server 1.pool.ntp.org
    server 2.pool.ntp.org
    restrict 0.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
    restrict 1.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery
    restrict 2.pool.ntp.org mask 255.255.255.255 nomodify notrap noquery

    # Clients
    restrict 127.0.0.1
    restrict 172.31.0.3 mask 255.255.255.255 nomodify notrap

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### Commands

    ntpdate -v 0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org
    ntpdate -v 0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org
    ntpdate -v 0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org
    chmod  +x /etc/rc.d/rc.ntpd
    /etc/rc.d/rc.ntpd restart
    ps -A | grep ntp
    sleep 60
    ntpq -p

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### Firewall

    iptables -A INPUT -p udp --dport 123 ! -s 172.31.0.3 -j DROP

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### Cisco config

    Cisco-3750#configure terminal 
    Cisco-3750(config)#ntp server 172.31.0.254
    Cisco-3750(config)#exit
    Cisco-3750#wri mem

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### Bookmark

    http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch24_:_The_NTP_Server

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_BY: Pejman Moghadam_  
_TAG: ntp, cisco_  
_DATE: 2012-08-18 11:08:01_