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Re: ping packet loss when size gt 1500

On Sat, 16 Oct 2010 20:11:46 +0100, Adam Hardy wrote:

> I thought I knew enough to keep my own home LAN going but I'm stuck on
> this one and I can't work out what to do next. In fact I thought
> everything was fine until I tried pinging with big packet sizes.
> ping -s 1472 www.bbc.co.uk
> ping -s 1472
> works fine, no packet loss ever.
> ping -s 1473 www.bbc.co.uk
> works fine too.
> ping -s 1473
> results in 100% packet loss.

It can be a black hole router.

Most firewalls block pings that send packets bigger than normal (32-64 
bytes) to avoid "ping of death" and "blocking icmp fragment".

> I have a bizarre problem with the server at, which is an
> internet broker whose server keeps disconnecting when making data
> requests. Their support is blaming the problem on me.

I cannot load that site ( on a web browser :-?

sm01@stt008:~$ host domain name pointer mktgw1.ibllc.com.

And by its name, seems like a gateway.

> is used by a huge number of clients and I apparently am
> the only one suffering.
> Could it be something on my LAN? Or could it be my ISP (British Telecom)
> whose DNS server will randomly go down for a while and then come back
> (not in sync with the appearance of this problem though) - I thought I'd
> state that to give an idea of the ISP's reliability.
> Or is this ping problem definitely something I can sort out and perhaps
> solve it?

You can try by reducing your MTU to 1400.



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