IPv6 Anycast?

IPv6 Anycast?

[Stuart Sheldon]

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Is IPv6 Anycast supported? And if so, how do I setup the Anycast addresses?

Please reply to me directly, as I am not on this list...

Thanks In advance,

Stu Sheldon
ACT USA

- --
Every year is getting shorter, never seem to find the time
Plans that either come to naught or half a page of scribbled lines
Hanging on in quiet desperation is the english way
The time is gone, the song is over, thought Id something more to say
               -- Pink Floyd - "Time Lyrics"
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Re: IPv6 Anycast?

[Mikael Abrahamsson]

On Thu, 22 Jul 2010, Stuart Sheldon wrote:

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> Is IPv6 Anycast supported? And if so, how do I setup the Anycast addresses?

Are you sure that's what you're looking for?

<http://en.wikipedia.org/wiki/Anycast>

Because that's more a function of routing protocol/network, than anything 
really related to "netdev".

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: IPv6 Anycast?

[Stuart Sheldon]

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Yea, I'm sure...

We use Linux for routers as well as servers and workstations. Since I
sent this I've discovered that by default, when a Linux system has IPv6
forwarding turned on, it adds the <network>::/64 anycast router
addresses on all the interfaces (as per rfc 2526).

What I'm actually looking to do is (change / add) other addresses the to
anycast6 list to work in an existing configuration that does not use the
rfc 2526 anycast router address.

Is there a command line method of setting up these anycast addresses?

Thanks,

Stu Sheldon
ACT USA


On 07/22/2010 08:57 PM, Mikael Abrahamsson wrote:
> On Thu, 22 Jul 2010, Stuart Sheldon wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA256
>>
>> Is IPv6 Anycast supported? And if so, how do I setup the Anycast
>> addresses?
> 
> Are you sure that's what you're looking for?
> 
> <http://en.wikipedia.org/wiki/Anycast>
> 
> Because that's more a function of routing protocol/network, than
> anything really related to "netdev".
> 

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Re: IPv6 Anycast?

[Mikael Abrahamsson]

On Thu, 22 Jul 2010, Stuart Sheldon wrote:

> Yea, I'm sure...
>
> We use Linux for routers as well as servers and workstations. Since I
> sent this I've discovered that by default, when a Linux system has IPv6
> forwarding turned on, it adds the <network>::/64 anycast router
> addresses on all the interfaces (as per rfc 2526).
>
> What I'm actually looking to do is (change / add) other addresses the to
> anycast6 list to work in an existing configuration that does not use the
> rfc 2526 anycast router address.
>
> Is there a command line method of setting up these anycast addresses?

In routers, this is done by adding the IP address to a loopback interface 
and announcing the address using a routing protocol, I don't see why this 
can't be done on a linux box?

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: IPv6 Anycast?

[Stuart Sheldon]

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Mikael,

Thanks for stepping up and helping me with this... I am aware of the
method of using the loopback adapter. This method is suggested when
doing things like DNS in a Anycast setup, and also works well with IPv4.
Here is a more detailed explanation of what I'm trying to make work...
If this is better addressed by another kernel group, please let me know,
as I'm unsure where this should be directed.

Currently, when you enable IPv6 forwarding on Linux, Linux automatically
creates an Anycast address for each interface. Here is an example:

cat /proc/net/anycast6
<empty_file>

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

cat /proc/net/anycast6
1    lo              00000000000000000000000000000001     1
2    eth0            2607ff38000000000000000000000000     1
2    eth0            fe800000000000000000000000000000     1
3    eth1            fe800000000000000000000000000000     1
3    eth1            2607ff38000000010000000000000000     1
4    eth2            fe800000000000000000000000000000     1
5    eth3            2607ff38000000020000000000000000     1
5    eth3            fe800000000000000000000000000000     1
6    eth4            fe800000000000000000000000000000     1

If you ping one of these auto configured Anycast addresses, let's say
eth0's 2607:ff38:: from another host on the eth0 network, you will get a
reply from the Linux route box. This allows you to set the default route
of that host to the Anycast address 2607:ff38:: and if you have multiple
routers on that LAN, it will add the one that responds first to it's
neighbor table. This way if one goes down, the host will automatically
swing over to another router (once the neighbor cache expires)...

Anycast addresses are addresses that are never used as a source address,
and are exempt from duplicate address detection (as per RFC 3513).

It would appear that the Linux kernel is automatically implementing the
reserved Anycast address referenced in RFC 2526. This would be cool,
except for a few things. what if you don't want the router to act as an
Anycast router on a particular network? How do you remove an Anycast
address? And, what if you want to use another address that isn't the
reserved address as your Anycast router address? How do you add / change
an Anycast address? The RFC regarding Anycast addresses is very clear
that it and be ANY unicast address.

What I'm looking for is an answer to how I can add/remove/change these
Anycast addresses.

Again, if I'm asking the wrong list, please point me in the right direction.

Thanks again!

Stu Sheldon
ACT USA




Mikael Abrahamsson wrote:
> On Thu, 22 Jul 2010, Stuart Sheldon wrote:
> 
>> Yea, I'm sure...
>>
>> We use Linux for routers as well as servers and workstations. Since I
>> sent this I've discovered that by default, when a Linux system has IPv6
>> forwarding turned on, it adds the <network>::/64 anycast router
>> addresses on all the interfaces (as per rfc 2526).
>>
>> What I'm actually looking to do is (change / add) other addresses the to
>> anycast6 list to work in an existing configuration that does not use the
>> rfc 2526 anycast router address.
>>
>> Is there a command line method of setting up these anycast addresses?
> 
> In routers, this is done by adding the IP address to a loopback
> interface and announcing the address using a routing protocol, I don't
> see why this can't be done on a linux box?
> 


- --
And you run and you run to catch up with the sun, but its sinking
And racing around to come up behind you again
The sun is the same in the relative way, but youre older
Shorter of breath and one day closer to death
               -- Pink Floyd - "Time Lyrics"
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Re: IPv6 Anycast?

[Ulrich Weber]

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Hi Stuart,

you probably mean the IPV6_JOIN_ANYCAST/IPV6_LEAVE_ANYCAST socket option
support? See the old patch documentation:
http://lkml.indiana.edu/hypermail/linux/net/0208.3/0028.html

To remove the automatic generated IPv6 Anycast addresses, you can remove
the routes from the local table manually:
ip -6 route del 2607:ff38:: table local

Best regards
 Ulrich

- -- 
Ulrich Weber | uweber@astaro.com | Software Engineer
Astaro GmbH & Co. KG | www.astaro.com | Phone +49-721-25516-0 | Fax –200
An der RaumFabrik 33a | 76227 Karlsruhe | Germany
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Re: IPv6 Anycast?

[Stuart Sheldon]

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Hi Ulrich,

Thanks, that resolves half the issue. So as of right now, there is no
userspace program to add anycast addresses?

Thanks in advance,

Stu Sheldon
ACT USA


Ulrich Weber wrote:
> Hi Stuart,
> 
> you probably mean the IPV6_JOIN_ANYCAST/IPV6_LEAVE_ANYCAST socket option
> support? See the old patch documentation:
> http://lkml.indiana.edu/hypermail/linux/net/0208.3/0028.html
> 
> To remove the automatic generated IPv6 Anycast addresses, you can remove
> the routes from the local table manually:
> ip -6 route del 2607:ff38:: table local
> 
> Best regards
>  Ulrich
> 

- --
Hey nineteen Thats retha franklin, She dont remember The queen of soul,
Its hard times befallen The sole survivors, She thinks Im crazy,
But Im just growing old
               -- Steely Dan - "Hey 19 - Lyrics"
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Re: IPv6 Anycast?

[Simon Horman]

On Fri, Jul 23, 2010 at 09:54:05AM -0700, Stuart Sheldon wrote:
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> 
> Hi Ulrich,
> 
> Thanks, that resolves half the issue. So as of right now, there is no
> userspace program to add anycast addresses?

I was hoping to have some useful information, but alas I failed on that count.

Looking at ip(8) it seems that the following ought to work:

ip addr add fd16:a2f5:c4d7::7/48 anycast fd16:a2f5:c4d7::8 dev eth0

However, it seems not to, and then I found this in the manpage :-(

	anycast   -   not  implemented  the  destinations are  anycast
	addresses assigned to this host.  They are mainly equivalent to
	local with one difference: such addresses are invalid when used as
	the source address of any packet.

Re: IPv6 Anycast?

[Stuart Sheldon]

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Hi Simon,

I found the ip man entry too... It appears that the code is in the
kernel, as it does automatically add the anycast addresses when you
start IPv6 routing...

Is this something I should file as a bug / feature request? I would
think this should be part of the iproute2 stuff, but LARTC seems to have
fallen off the planet. I'm an Administrator not really a programmer, and
this seems way beyond my hacking to get done. Not really sure where to
go from here...

Does anyone out there have any suggestions???

Thanks in advance...

Stu


Simon Horman wrote:
> On Fri, Jul 23, 2010 at 09:54:05AM -0700, Stuart Sheldon wrote:
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA256
>>
>> Hi Ulrich,
>>
>> Thanks, that resolves half the issue. So as of right now, there is no
>> userspace program to add anycast addresses?
> 
> I was hoping to have some useful information, but alas I failed on that count.
> 
> Looking at ip(8) it seems that the following ought to work:
> 
> ip addr add fd16:a2f5:c4d7::7/48 anycast fd16:a2f5:c4d7::8 dev eth0
> 
> However, it seems not to, and then I found this in the manpage :-(
> 
> 	anycast   -   not  implemented  the  destinations are  anycast
> 	addresses assigned to this host.  They are mainly equivalent to
> 	local with one difference: such addresses are invalid when used as
> 	the source address of any packet.
> 


- --
Does anyone know where the love of God goes when the waves turn the
minutes to hours. The searchers all say that they'd have made
White Fish Bay if they'd put fifteen more miles behind her.
   -- Gordon Lightfoot "The Wreck of The Edmund Fitzgerald Lyrics"
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