On 03/11/14 13:34, Brian Bockelman wrote:
> Hi Andy,
>
> No, the xrootd on srm.unl.edu was not launched with any special flag (it's a bit on the older side FWIW).
>
> I think what's happening is the client is resolving both IPv6 and IPv4 addresses of the server and preferring the IPv6 one over IPv4 (this is not controllable through DNS) despite the fact there's no valid IPv6 route to the outside world.

Yes, that was it. And our hosts/network does not know what to do with it so all 
connection attempts failed immediately.

Matevz

> Brian
>
> On Mar 11, 2014, at 3:24 PM, Andrew Hanushevsky <[log in to unmask]> wrote:
>
>> Hi Brian,
>>
>> Presumably the xrootd running at srm.unl.edu was started with the "-I v4" option, yes? The server, by default, binds to an IPV4 mapped address if it has no IPV6 address. But that doesn't preclude IPV4 clients from connecting to it either way (I do that all the time). The reverse should also work as long as the server. I think the client does the same kind of thing. It comes down to the fact that the DNS has to be setup correctly for all this to work.
>>
>> Andy
>>
>> -----Original Message----- From: Brian Bockelman
>> Sent: Tuesday, March 11, 2014 1:02 PM
>> To: Andrew Hanushevsky
>> Cc: Matevz Tadel ; xrootd-dev
>> Subject: Re: Fun with ipv6
>>
>> Hi,
>>
>> Is it not possible to have the client use AI_ADDRCONFIG by default?
>>
>> To give more info - srm.unl.edu resolves on both v4 and v6, but is running a version of xrootd server which only binds on the v4 address.
>>
>> Brian
>>
>> On Mar 11, 2014, at 2:38 PM, Andrew Hanushevsky <[log in to unmask]> wrote:
>>
>>> Hi Matevz,
>>>
>>> Please use the command line option "-I v4". See: http://xrootd.org/doc/dev4/xrd_config.htm#_Toc380525636
>>> You need to use it for the cmsd *and* the xrootd to avoid address conflicts.
>>>
>>> As for using which address, it depends on how the DNS was setup. Some people do it correctly other do not (though that is being increasingly rare). The redirector prefers a IPV4 address over an IPV6 address but will use an IPV6 address if you happen to come in with an IPV6 address. If you come in with an IPV4 address but there is no IPV4 address for the target server, the redirection will fail. Most of the time it doesn't matter because the redirector will preferentially use the hostname whenever possible and let DNS sort things out (which may or may not work, depending on the experience of your network people). The only issue is locate which is used way too often as this returns actual IP addresses (well, it can return hostnames but you have to ask for that).
>>>
>>> In the end, let me point out that having a mixed mode IP address configuration is always going to be problematic and sites should start worrying about it now as we transition to IPV6 (though some pundits say that will never happen).
>>>
>>> Andy
>>>
>>> -----Original Message----- From: Matevz Tadel
>>> Sent: Tuesday, March 11, 2014 12:23 PM
>>> To: xrootd-dev
>>> Subject: Fun with ipv6
>>>
>>> Hi,
>>>
>>> Apparently xrootd proxy from the master branch will prefer an ipv6 address over
>>> an ipv4 one ... this is giving me grief as apparently our machines here are not
>>> configured to handle it and local redirector at UNL (srm.unl.edu) has both ipv4
>>> and 6 addresses.
>>>
>>> I tried turning this off on the proxy host (via /etc/gai.conf) but it didn't
>>> help. Is there a config hammer to turn ipv6 off? :)
>>>
>>> Matevz
>>>
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