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Router's LAN facing interface becomes up/down frequently

Hi there,

We have a 1841 Cisco router for one of our remote sites and we have the GRE over IPSec tunnel on it (with our datacenter router) for the connectivity. The LAN facing interface becomes UP/Down (status 'UP', Protocol 'Down'). When I login the router and 'shut' and then 'no shut' the interface, the interface becomes UP and everything starts to work. Traffic starts to flow across it. But after some time, some hours or sometimes some days, the interface is again back to up/down status. The router is connected to  a non-Cisco switch. I do see some CRC's increasing very slowly, but apart from that there seems nothing wrong with the interface in sho int fas0/0 command:


RTR01#sho int fas0/0

FastEthernet0/0 is up, line protocol is down

  Hardware is Gt96k FE, address is 0026.cb91.ee48 (bia 0026.cb91.ee48)


  Internet address is

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, 100BaseTX/FX

  ARP type: ARPA, ARP Timeout 04:00:00

  Last input 00:07:47, output 00:07:47, output hang never

  Last clearing of "show interface" counters 01:52:43

  Input queue: 0/75/20417/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 16000 bits/sec, 39 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     979983 packets input, 93907374 bytes

     Received 927358 broadcasts, 0 runts, 0 giants, 0 throttles

     261 input errors, 261 CRC, 0 frame, 0 overrun, 0 ignored

     0 watchdog

     0 input packets with dribble condition detected

     142760 packets output, 20987130 bytes, 0 underruns

     0 output errors, 0 collisions, 2 interface resets

     0 babbles, 0 late collision, 0 deferred

     0 lost carrier, 0 no carrier

     0 output buffer failures, 0 output buffers swapped out


The cofiguration on the interface is just : speed 100, dup full, the IP address and the helper-addresses..  Could it be because of any bug..

Hall of Fame Super Gold

Router's LAN facing interface becomes up/down frequently

Try swapping out the LAN cable.

You have CRC errors.  Ensure your speed and duplex setting are "auto".