Hi All,

Could you please let me know if there is any
limit on how many IPv6 addresses an interface.
I searched for a result but could not find any
conslusive answer. Could anybody please.

Regards,
Arul Kumar C

Arul Kumar C <arulkumar.c@gmail.com> writes:
> Could you please let me know if there is any
> limit on how many IPv6 addresses an interface.
> I searched for a result but could not find any
> conslusive answer. Could anybody please.

That's probably because there is no answer. An interface may have
zero, one, or many IPv6 addresses. If there are limits, then they're
defined by the implementation, not the protocol. (I don't know of any
implementation that has such a limit.)

--
James Carlson, Solaris Networking <james.d.carlson@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

Hi James,

Thanks for your clarification.

The Cisco implementation states in a note.

The maximum number of IPv6 addresses (static and autoconfigured)
allowed on an interface is eight, except on the management (mgmt 0)
interface where only one static IPv6 address can be configured.

http://www.cisco.com/en/US/products/...html#wp1121869

Regards,
Arul Kumar C

On Apr 26, 3:46 pm, James Carlson <james.d.carl...@sun.com> wrote:
> Arul Kumar C <arulkuma...@gmail.com> writes:
>
> > Could you please let me know if there is any
> > limit on how many IPv6 addresses an interface.
> > I searched for a result but could not find any
> > conslusive answer. Could anybody please.
>
> That's probably because there is no answer. An interface may have
> zero, one, or many IPv6 addresses. If there are limits, then they're
> defined by the implementation, not the protocol. (I don't know of any
> implementation that has such a limit.)
>
> --
> James Carlson, Solaris Networking <james.d.carl...@sun.com>
> Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
> MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

Arul Kumar C <arulkumar.c@gmail.com> writes:
> Thanks for your clarification.
>
> The Cisco implementation states in a note.
>
> The maximum number of IPv6 addresses (static and autoconfigured)
> allowed on an interface is eight, except on the management (mgmt 0)
> interface where only one static IPv6 address can be configured.

Though that appears true for their implementation, other
implementations will certainly vary. (Even other platforms from the
same vendor may vary.)

I suppose it doesn't surprise me much that an embedded system has
design limitations. Most general-purpose systems don't, though.

I think the real question is: why did you ask?

--
James Carlson, Solaris Networking <james.d.carlson@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

In article <xoavlkgdyi09.fsf@sun.com>,
James Carlson <james.d.carlson@sun.com> wrote:

>Though that appears true for their implementation, other
>implementations will certainly vary. (Even other platforms from the
>same vendor may vary.)

yes, that's the point of talking about *implementation* limitations.


>I suppose it doesn't surprise me much that an embedded system has
>design limitations. Most general-purpose systems don't, though.

Perhaps most general-purpose systems explicit, documented limits on
the number of addresses they allow, but the classic BSD kernel
ifa_ifwith*addr*() functions tend to fall over if you configure a few
1000 IP aliases. I see that FreeBSD 5.4 still uses linear searching.

Long ago A UNIX vendor of my acquaintance hacked on the BSD net/if.c
to use hash tables instead of linear searching. That was before
HTTP included server host names and when an ISP customer or two
thought it better to serve 1000's of small customers with a few big
boxes instead of 1000's of small boxes. I thought it was a bad idea
and that customers who wanted such things should be told to to find a
UNIX system vendor dumb enough to make such changes for the supposed
market of giant boxes serving zillions of domains each with its own
IP address. No one listened to me before, during, or after the saga
of bugs and other problems with the new code. It's not a change that
is as easy as it sounds and it leaves permanent complications. I didn't
even get a real chance to say "I told you so" when the customer's
business proved fatally unprofitable for more fundamental but almost
as obvious reasons.


>I think the real question is: why did you ask?

agreed.


Vernon Schryver vjs@rhyolite.com

In article <f0t6mc$1pvb$1@calcite.rhyolite.com>,
vjs@calcite.rhyolite.com (Vernon Schryver) wrote:

> In article <xoavlkgdyi09.fsf@sun.com>,
> James Carlson <james.d.carlson@sun.com> wrote:
>
> >Though that appears true for their implementation, other
> >implementations will certainly vary. (Even other platforms from the
> >same vendor may vary.)
>
> yes, that's the point of talking about *implementation* limitations.

When did you say you were talking about implementation limitations?
Your initial post seemed to be asking about protocol limitations.

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

On Apr 27, 9:00 pm, v...@calcite.rhyolite.com (Vernon Schryver) wrote:
> In article <xoavlkgdyi09....@sun.com>,
> James Carlson <james.d.carl...@sun.com> wrote:
>
> >Though that appears true for their implementation, other
> >implementations will certainly vary. (Even other platforms from the
> >same vendor may vary.)
>
> yes, that's the point of talking about *implementation* limitations.
>
> >I suppose it doesn't surprise me much that an embedded system has
> >design limitations. Most general-purpose systems don't, though.
>
> Perhaps most general-purpose systems explicit, documented limits on
> the number of addresses they allow, but the classic BSD kernel
> ifa_ifwith*addr*() functions tend to fall over if you configure a few
> 1000 IP aliases. I see that FreeBSD 5.4 still uses linear searching.
>
> Long ago A UNIX vendor of my acquaintance hacked on the BSD net/if.c
> to use hash tables instead of linear searching. That was before
> HTTP included server host names and when an ISP customer or two
> thought it better to serve 1000's of small customers with a few big
> boxes instead of 1000's of small boxes. I thought it was a bad idea
> and that customers who wanted such things should be told to to find a
> UNIX system vendor dumb enough to make such changes for the supposed
> market of giant boxes serving zillions of domains each with its own
> IP address. No one listened to me before, during, or after the saga
> of bugs and other problems with the new code. It's not a change that
> is as easy as it sounds and it leaves permanent complications. I didn't
> even get a real chance to say "I told you so" when the customer's
> business proved fatally unprofitable for more fundamental but almost
> as obvious reasons.
>
> >I think the real question is: why did you ask?
>
> agreed.

I am trying to write in linux an management application for
interface. I am
not sure of how many IPv6 address that i should accept from users.

Regards,
Arul Kumar C


>
> Vernon Schryver v...@rhyolite.com

Arul Kumar C <arulkumar.c@gmail.com> writes:
> > >I think the real question is: why did you ask?
> >
> > agreed.
>
> I am trying to write in linux an management application for
> interface. I am
> not sure of how many IPv6 address that i should accept from users.

I think the right answer, then, should be "all of them."

--
James Carlson, Solaris Networking <james.d.carlson@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

In article <xoavd51j2rjp.fsf@sun.com>,
James Carlson <james.d.carlson@sun.com> wrote:

>> I am trying to write in linux an management application for
>> interface. I am
>> not sure of how many IPv6 address that i should accept from users.
>
>I think the right answer, then, should be "all of them."

I would add 'until the underlying system call or system("ifconfig")
interface refuses'.
That would handle not only the "too many" case (if it exists) and other
problems such as duplicates or bad netmasks not caught by the GUI.

Another obvious tactic is to try `ifconfig` on 10,000 addresses to
find the limit, if it exists.


Please congratulate me for suppressing my reflecive rant about how
such "management applications" are too often written by people who
lack sufficient knowledge and experience to use, not to mention
write them. Just because a pointy haired boss thinks telling someone
to write....oops, I guess I blew any congratulations.


Vernon Schryver vjs@rhyolite.com