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enedebe
Asked: 2012-05-16 08:06:50 +0800 CST

Ethernet fails just for seconds

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I have a clearos gateway linux working as gateway. I have some problems with the conectivity, everything works great but for a few seconds internal ethernet stops working. After 5-10 seconds, it works again.

I did a ping to internet and from the gateway I didn't find any packet lost, but from a computer in the intranet I get some problems:

Request timeout for icmp_seq 94
92 bytes from mygateway.ar7 (192.168.1.1): Destination Net Unreachable
Vr HL TOS  Len   ID Flg  off TTL Pro  cks      Src      Dst
 4  5  00 5400 81f5   0 0000  40  01 054f 192.168.1.156  74.125.230.163

This is my ifconfig eth2 

eth2  Link encap:Ethernet  HWaddr XX:XX:XX:XX:XX:XX  
      inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
      inet6 addr: fe80::212:79ff:fe5f:c291/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:7525730 errors:0 dropped:0 overruns:0 frame:0
      TX packets:8134818 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:3353100361 (3.1 GiB)  TX bytes:3048405269 (2.8 GiB)
      Interrupt:169 Memory:f0400000-f0410000

What can be the problem? Local DNS server? Switch? Network loop?

Any idea?

Thanks!

linux ethernet linux-networking

2 Answers

  1. 92 bytes from mygateway.ar7 (192.168.1.1): Destination Net Unreachable

    This right here means that the problem isn't on your local network. Your internal machine is getting a reply from your gateway saying that the internal machine can't reach the destination network.

    You've already said the gateway itself doesn't have problems so the problem is likely due to some sort of policy. Does it have any sort of connection or ICMP throttling in place?

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  2. You may have a disabled port on another server that has a duplicate IP configured. I have seen numerous times that even disabled ports will cause intermittent IP address conflicts. I know it sounds ridiculous but the problem has always gone away when I remove the address info instead of just allowing the OS to grey them out. Its worth a try.

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