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Keepalive problem

After connection Android device with JP1081 USB Ethernet adapter to Cisco 2960, the port to which the device is turned off. Android device with JP1081 operates in 10Mb/half-duplex.

What is the cause of failures and how to solve this problem?

The log shows the following entries:

ruekasw13#sh run int Fa0/20

Building configuration...

Current configuration : 51 bytes


interface FastEthernet0/20

  description -tv


Dec 18 05:49:25: %LINK-3-UPDOWN: Interface FastEthernet0/20, changed state to up

Dec 18 05:49:26: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/20, changed state to up


Dec 18 05:49:58: %ETHCNTR-3-HALF_DUX_COLLISION_EXCEED_THRESHOLD: Collisions at FastEthernet0/20 exceed threshold. Considered as loop-back.


Dec 18 05:49:58: %PM-4-ERR_DISABLE: loopback error detected on Fa0/20, putting Fa0/20 in err-disable state

Dec 18 05:49:59: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/20, changed state to down


Dec 18 05:50:00: %LINK-3-UPDOWN: Interface FastEthernet0/20, changed state to down

ruekasw13#sh int Fa0/20   

FastEthernet0/20 is down, line protocol is down (err-disabled)

   Hardware is Fast Ethernet, address is 203a.0765.1314 (bia 203a.0765.1314)

   Description: -tv

   MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

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

   Encapsulation ARPA, loopback not set

   Keepalive set (10 sec)

   Auto-duplex, Auto-speed, media type is 10/100BaseTX

   input flow-control is off, output flow-control is unsupported

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

   Last input never, output 00:03:09, output hang never

   Last clearing of "show interface" counters never

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

   Queueing strategy: fifo

   Output queue: 0/40 (size/max)

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

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

      4377 packets input, 795370 bytes, 0 no buffer

      Received 487 broadcasts (51 multicasts)

      0 runts, 0 giants, 0 throttles

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

      0 watchdog, 51 multicast, 0 pause input

      0 input packets with dribble condition detected

      82202 packets output, 10111549 bytes, 0 underruns

      0 output errors, 162 collisions, 3 interface resets

      0 babbles, 0 late collision, 0 deferred

      0 lost carrier, 0 no carrier, 0 PAUSE output

      0 output buffer failures, 0 output buffers swapped out

Everyone's tags (3)
VIP Purple

Re: Keepalive problem

Hi Granov,

collisions are a just normal part of the half-duplex CSMA/CD procedure, and are not considered errors at all.  They are just retried.  They are not considered errors until a packet suffers 16 of them in a row, and has to be discarded - known as "excessive collisions".

1. Disable the keepalive with these commands:

Switch#config t

Switch(config)# int f0/20

Switch(config-if)# no keepalive

2. If you don't want to turn off loopback detection/shutdown, you should

definitely enable loopback recovery (off by default, requiring manual

reset, an *awful* default!):

errdisable recovery cause loopback

errdisable recovery interval 60

3. run no shut on the interface fa0/20


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