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Cisco Bug: CSCvv34333 - NTP is unable to synchronise even when NTP messages are exchanged

Last Modified

Aug 25, 2020

Products (1)

  • Cisco IOS

Known Affected Releases


Description (partial)

NTP messages are received but router just ignore packets
Stops working after about 5 minutes

configuration is below:

ip-cosg-ch-bsg-mr-007#show run | section ntp
ntp authentication-key 1 md5 <password>
ntp authenticate
ntp trusted-key 1
ntp source Loopback0
ntp update-calendar
ntp server prefer
ntp server

Connection to NTP server prefer is working with no drops:

ip-cosg-ch-bsg-mr-007#ping source lo0 rep 1000
Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to, timeout is 2 seconds:
Packet sent with a source address of
Success rate is 100 percent (1000/1000), round-trip min/avg/max = 20/38/132 ms

Confirmed same NTP server is working with other NTP clients.
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