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Author Topic: mtu set wrongly at hurricane end  (Read 2721 times)

dcottle

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mtu set wrongly at hurricane end
« on: March 01, 2011, 05:40:58 PM »

I have got MTU issues. I am on PPPoA so I have 1500.

My system adds the sit1 for hurricane at 1480.

Why when I ping6 -s 1500 does it then reply randomly with max mtu size is 1472 and I get lost packets?

I have verified I do have 1500 MTU tested over ipv4

I tried setting my sit1 with IPV6_MTU=1472 but I restarted the network it's still 1480

« Last Edit: March 01, 2011, 05:46:10 PM by dcottle »
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cconn

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Re: mtu set wrongly at hurricane end
« Reply #1 on: March 02, 2011, 02:22:16 PM »

you may have PPPoA at 1500 but tunneling adds overhead.

http://www.potaroo.net/ispcol/2010-05/v6hints.html
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dcottle

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Re: mtu set wrongly at hurricane end
« Reply #2 on: March 02, 2011, 05:15:57 PM »

Yes, it should be 1480

What is happening, my connection is fine. Clients tested with ipv6 test and pass large packets 10 out of 10.

My server also passes also.

I got some web sites set on my server.  When I try to access them pages stall during loading. I try dropping MTU no change.  It seems to be a HE tunnel to another HE tunnel.

I send some large 1500 and 2000 ICMP. On the first attempt, 50 to 75 % loss.  As I then try smaller packets, it then goes to 0 % loss.  I then can send huge 3000 and 5000 no loss or errors.

Leave it about 20 minutes and the first attempt lost packets again.

Seems something out of my control is not working properly.  I see this with my sites. Sometimes the load perfectly, other times stall.  Anyone with native ipv6 has no problems .

I am thinking of setting up a cron job to simply send 4 long ping6 every 10 minutes to see if it fixes the issue.

Again it's purely a HE to HE tunnel issue / glitch.  Dropping MTU does nothing, even 1280 and no change.

It is also weird why first pings loose 75% and then goes perfect.
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