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Input and CRC errors on ASA 5505 outside interface


I see input and crc errors on my ASA 5505  eth0/0(outside) interface and packet drops. There is very slow connection though we have 20mb line. ISP also sees the issue on the Lan interface side. We have the speed and duplex configured same on both ISP and our end.

I am suspecting if this is Physical cable issue. Please suggest.

  Hardware is 88E6095, BW 100 Mbps, DLY 100 usec

        Full-Duplex(Full-duplex), 100 Mbps(100 Mbps)

        Input flow control is unsupported, output flow control is unsupported

        Available but not configured via nameif

        MAC address 001a.b4c9.f3d9, MTU not set

        IP address unassigned

        158138067 packets input, 141061681082 bytes, 0 no buffer

        Received 183037 broadcasts, 0 runts, 0 giants

        19642 input errors, 19642 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

        0 pause input, 0 resume input

        0 L2 decode drops

        144684 switch ingress policy drops

        124291353 packets output, 38197278051 bytes, 0 underruns

        0 pause output, 0 resume output

        0 output errors, 0 collisions, 0 interface resets

        0 late collisions, 0 deferred

        0 rate limit drops

        0 switch egress policy drops

        0 input reset drops, 0 output reset drops

Everyone's tags (2)
Super Bronze

Input and CRC errors on ASA 5505 outside interface


What do you mean by the LAN side? Do you mean that you see problems on the ASAs physical LAN interface or perhaps on the device in front of the ASA and on the port that is connected to the ASA external interface?

I guess it would point to a problem with the cable if both ends are seeing input/CRC errors.

You can naturally try switch the physical ports if possible.

- Jouni

New Member

Input and CRC errors on ASA 5505 outside interface

HI JouniForss,

No, its not the ASA physical lan interface but on the Lan port of ISP managed router which is connecting to ASA external interface. yes we see the errors on both ends and thats the reason i suspect the cable issue.

i just want to plug out the cable between those two and put back and also try to change the cable and check to see if it resolves the issue.

Do you suggest to change the ports if the above things doesn't work?

Super Bronze

Input and CRC errors on ASA 5505 outside interface


To be honest I have not had to troubleshoot these kind of issues but I would assume if both ends are receiving traffic that is dropped because of CRC errors then the problem would either be the cable or both ports would be somehow faulty.

Most of the time the problem has been on a physical device on one side through. Rarely on both ends. Sometimes its a mangled cable that has caused problems.

- Jouni

Input and CRC errors on ASA 5505 outside interface

Hello Ravi,

This kind of issues CRCs/ Input Errors are tipically known as L1 issues so make sure you check the cable and if that does not make a difference change the port on each side to see if there is a difference.

Unfortunetly the ASA does not support the Time-Domain Reflectometer feature so we must do the test of L1 by ourselfs.

Can you clear the counters of the interface, test the changes provided and provide us some feedback?

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Julio Carvajal Segura

Julio Carvajal
Senior Network Security and Core Specialist
New Member

Input and CRC errors on ASA 5505 outside interface

Thanks Jouni/Julio.  I will test and let you know the details.

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