Solved - Re: IPv6 mtu restriction - stupid firewall rules

Robert Moskowitz rgm at htt-consult.com
Thu Mar 27 20:17:23 UTC 2014


Just 'forgot' which vlan this server was on internally, so I set the 
rules on the wrong vlan.

Well back to your regularly programmed...

On 03/27/2014 03:55 PM, Robert Moskowitz wrote:
>
> On 03/27/2014 03:40 PM, poma wrote:
>> On 27.03.2014 20:35, Robert Moskowitz wrote:
>>> On 03/27/2014 12:50 PM, Robert Moskowitz wrote:
>>>> This is from a Fedora 20 client testing to a Centos 6.5 server.
>>>>
>>>> I can do a ping6 with no problems, but I cannot 'ssh -6' to the server
>>>> (ssh -4 works).  I have reason to suspect the challenge is in my PPPoE
>>>> link with a restricted MTU size that v6's PMTU is not working right 
>>>> with.
>>>>
>>>> So my question is:  Is there a way to specify the MTU size for things
>>>> like ssh (and http) to use?
>>> I was told that:
>>>
>>> To figure out where I could put new MTU values:
>>> “find /sys |grep mtu”
>>>
>>> To set the MTU for my eth0, as root:
>>> “echo 1300 > 
>>> /sys/devices/pci0000:00/0000:00:03.0/0000:02:00.0/net/eth0/mtu”
>>>
>>> "ifconfig eth0" reports an MTU of 1300 now.
>>>
>>>
>>> And this works.  But it is not my problem.  Still not getting a TCP 
>>> connection.  Going to have to check with wireshark. Maybe it will 
>>> help me...
>>>
>> Considering how much data you've provided us. :)
>
> I was told elsewhere that my ipv6 problem was an mtu path discovery 
> problem.  Try forcing my mtu so that it will get through whatever path 
> (claim PPPoE link is the problem).  So, all I was asking was how to 
> set the mtu for a tcp connection.  I asked here and on the list where 
> I was testing the ipv6 app.  There someone said, not be app, but by 
> interface, and showed how he did it.  So that is the story to now.  
> But a 1300 mtu still does not work.  So fire up wireshark.  I think it 
> is a firewall problem.  SO I will go away again and look at the 
> firewall.....
>
>



More information about the users mailing list