[SWLUG] Helping me debug network issue

[Daniel Morgan]

yeah, the ping failed before and after the ping you advised, however I
followed your advice and upped the MTU to 1500 using.

/sbin/ifconfig eth0 mtu 1500

This seemed to work a treat, my network is now back up and running
thank you very much. The sysadmin had upgraded firmware on the router
earlier I am guessing based on your comments that it is related.

On Mon, Jan 9, 2012 at 3:09 PM, Curon Davies <cwd24 at cantab.net> wrote:
> You're MTU (1200) is already set quite low, so maybe it's not that, but if
> this fails then if could be:
>
> ping -s 1200 -c 1 google.co.uk
>
> Ideally the interface should work with an MTU of 1500 although routers can
> be problematic, particularly when VPNs are thrown in. Could it be that the
> MTU is too low and that the router isn't handling fragmentation correctly?
> (or have you already tried a higher value?)
>
> Curon
>
> The RX errors is rather high.
>
> On 9 January 2012 14:58, Daniel Morgan <plodski at gmail.com> wrote:
>>
>> heres the results of that:
>>
>>
>> ping -s 512 -c 400 -f -n www.google.co.uk
>> PING www-cctld.l.google.com (173.194.67.94) 512(540) bytes of data.
>>
>> --- www-cctld.l.google.com ping statistics ---
>> 400 packets transmitted, 400 received, 0% packet loss, time 5597ms
>>
>>
>> and my ifconfig for MTU
>>
>> root at daniel-debian:/etc# ifconfig
>>
>> eth0      Link encap:Ethernet  HWaddr 00:1a:a0:13:78:4f
>>          inet addr:172.16.1.15  Bcast:172.16.3.255  Mask:255.255.252.0
>>          UP BROADCAST RUNNING MULTICAST  MTU:1200  Metric:1
>>          RX packets:64836 errors:1563 dropped:0 overruns:0 frame:1563
>>          TX packets:52740 errors:0 dropped:0 overruns:0 carrier:0
>>          collisions:0 txqueuelen:1000
>>          RX bytes:7076832 (6.7 MiB)  TX bytes:4097326 (3.9 MiB)
>>          Interrupt:17
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