From: asadovnikov (asadovnikov@comcast.net)
Date: Sat Feb 12 2005 - 19:54:16 GMT-3
You have 3 options:
- do not assign a global unicast prefix to the link, use link-local IPv6
addressing only (assuming no end stations are on the segment)
- manually assign IPv6 global unicast to at least one router, or better yet
both routers
- use ipv6 address eui-64
(http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123cgcr/ipv
6_r/ipv6_05g.htm#wp1913162) to assign IPv6 global unicast to one or better
both routers, this option would require you only assign the prefix manually
while the host part is constructed automaticly.
The autoconfiguration option is really more for the host versus to the
router and does require a functional router to be present. Although it is
perfectly possible to only configure one router and autoconfigure all other
routers, it would not be desirable under most conditions as then whole
segment relies upon that router to be up and functioning, which does not
work well in most cases (sometimes when one router is a 'hub' and others are
stub spokes it may be acceptable though).
Best Regards,
Alexei
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Saturday, February 12, 2005 4:24 PM
To: simon hart; Group Study
Subject: Re: ipv6 address autoconfig
Hey Simon,
Thanks for getting back to me.
What you described is essentially like the stateless autoconfig process ipv6
nodes use to acquire ipv6 addresses. I'm somewhat familiar with this
process.
What I was really trying to understand is this:
Suppose this were your network.
rtr A rtr B
|----- sub 1 ------|
Can I configure both rtr A's and B's interfaces connected to sub 1 with ipv6
address autoconfig? Or, would one of those interfaces have to be hard coded
with either a global or site ipv6 prefix?
Thanks again. Tim
----- Original Message -----
From: "simon hart" <simon.hart@btinternet.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study" <ccielab@groupstudy.com>
Sent: Saturday, February 12, 2005 11:19 AM
Subject: RE: ipv6 address autoconfig
> Hi see if can help.
>
> As far as I know this is normally used on Multicast Media and is a means
by
> which an interface (or NIC) can determine both its local and globally
scoped
> IPv6 address.
>
> First the Interface will generate a Link Local address by prefixing its
own
> MAC address to the well known link local prefix FE80::/10. The Interface
> will then send out a Router Solicitation message (although it could just
> wait for a Router Advertisement message).
>
> Next the interface will send a Neighbor solicitation message - this is to
> make sure that no one else is using the link-local prefix. If the address
> is in use by another interface then this interface will recieve a Neighbor
> advertisement message. If this is the case, then IPv6 stateless
> autoconfiguration will terminate. The IP address will have to applied in
> another manner (ie DHCPv6 or Manual configuration).
>
> The Interface will now listen for Router Advertisement messages (these
> messages are multicast periodically on the link - the message is contained
> within an ICMPv6 packet). The Interface can, from these messages,
determine
> its Globally Scoped address (IPv6 aggregatable unicast address) eg:
> 2001:0408:001F::/64. Armed with this information the interface can now
> apply this prefix and thus talk locally and to the rest of the world in
IPv6
> speak.
>
> I believe that Cisco Routers will automatically pick up the Link Local
> address by default (that is FE80::/10 + MAC address). Therefore the
command
> IPv6 address autoconfig will allow the router to pick up a Globally
> significant address. This saves having to type out long hex numbers on
each
> interface, or having to use DHCP.
>
> Simon
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> ccie2be
> Sent: 12 February 2005 15:35
> To: Group Study
> Subject: ipv6 address autoconfig
>
>
> Hi guys,
>
> What pre-requisites, if any, exist for using this command?
>
> I can see from the command reference below what this command does but I
> don't understand when I can or should use this command. If someone can
> provide a simple example or scenario that illustrates how this command
> should or shouldn't be used, I would be very grateful.
>
> Thanks, Tim
>
> ipv6 address autoconfig
> To enable automatic configuration of IPv6 addresses using stateless
> autoconfiguration on an interface and enable IPv6 processing on the
> interface, use the ipv6 address autoconfig command in interface
> configuration mode. Addresses are configured depending on the prefixes
> received in Router Advertisement messages. To remove the address from the
> interface, use the no form of this command.
> ipv6 address autoconfig
> no ipv6 address autoconfig
>
> Syntax Description
> This command has no keywords or arguments.
>
> Defaults
> No IPv6 address is defined for the interface.
>
> Command Modes
> Interface configuration
>
> Command History
> Release Modification
> 12.2(13)T This command was introduced.
>
>
>
> Usage Guidelines
> If the Cisco IOS software detects another host using one of its IPv6
> addresses, it will display an error message on the console.
> The system automatically generates a link-local address for an interface
> when IPv6 processing is enabled on the interface, typically when an IPv6
> address is configured on the interface.
> If router advertisements (RAs) received on this interface have the "other
> configuration" flag set, then the interface will also attempt to acquire
> other configuration (i.e., non-address) using DHCP for IPv6.
> Examples
> The following example assigns the IPv6 address automatically.
> Router(config)# interface ethernet 0
>
> Router(config-if)# ipv6 address autoconfig
>
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