Category: Cisco

If you get this message on logs:

VFR-4-FRAG_TABLE_OVERFLOW: Dialer0: the fragment table has reached its maximum threshold 16

usually indicates than you are receiving a high number of fragmented packets. It may happens using p2p applications like torrent or emule, under an fragmentation packet attack or another causes.

You can increase this value and check if warnings disappear:

router(config-if)#ip virtual-reassembly max-reassemblies 64

Enter in config mode:

router#configure t

First configure a DNS server to resolve ntp servers name:

router(config)#ip name-server 8.8.8.8

Now set a primary ntp server:

router(config)#ntp server 0.europe.pool.ntp.org

And also a secondary:

router(config)#ntp server 1.europe.pool.ntp.org

Finally configure the time zone, here CET + 1:

router(config)#clock timezone CET 1

Exit from configuration mode and test the status, usually is necessary to wait for a few minutes to get a successful synchronization. Output can be similar to this:

router# show ntp status

Clock is synchronized, stratum 3, reference is 178.16.23.50
nominal freq is 249.9684 Hz, actual freq is 249.9665 Hz, precision is 2**16
reference time is DA07DA35.B8AE53C5 (15:40:20.721 CET Tue Ago 4 2015)
clock offset is -0.0009 msec, root delay is 0.11 msec
root dispersion is 0.08 msec, peer dispersion is 0.01 msec
loopfilter state is 'CTRL' (Normal Controlled Loop), drift is 0.000007607 s/s
system poll interval is 1024, last update was 567 sec ago.

And test the association server status too:

router# show ntp associations

address         ref clock       st   when   poll reach  delay  offset   disp
*~178.16.23.50   75.12.230.181    2    907   1024   377 86.323  -0.927 13.845
~37.247.53.178   129.242.4.241    2    904   1024   377 86.323  -0.927 14.845
* sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured