Creation of IPv6 link-local addresses

[Trond Endrestøl]

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Hi,

Questions regarding IPv6 may not belong here, but I take my chances 
anyway.

Subsection 5.3 of RFC 2462 states that:

  ``A node forms a link-local address whenever an interface becomes 
    enabled [...]''

One of the events listed in Subsection 5.3 is when:

  ``The interface becomes enabled by system management after having 
    been administratively disabled.''

On one of the systems I manage, I use vlan devices cloned from one of 
the two physical interfaces.

Here's a slightly edited output from ifconfig:

xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=9<RXCSUM,VLAN_MTU>
        inet6 fe80::250:4ff:fe43:9d15%xl0 prefixlen 64 scopeid 0x1
        inet6 2001:XXXX:YYYY:ZZZZ:250:4ff:fe43:9d15 prefixlen 64 autoconf
        ether 00:50:04:43:9d:15
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
dc0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        options=8<VLAN_MTU>
        inet6 fe80::204:e2ff:fe39:29c6%dc0 prefixlen 64 scopeid 0x2
        ether 00:04:e2:39:29:c6
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet6 fe80::250:4ff:fe43:9d15%vlan0 prefixlen 64 scopeid 0x4
        ether 00:04:e2:39:29:c6
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
        vlan: 40 parent interface: dc0

First, the link-local address on the vlan0 interface is based on the 
link-layer address of the primary interface, xl0, yet the vlan 
interface has the other physical interface, dc0, as its parent 
interface.

Second, the link-layer address is not recreated when I do an 
``ifconfig vlan0 down'' followed by an ``ifconfig vlan0 up''.

It seems like the IPv6 stack needs some refurbishment.

Can I set additional link-local addresses on the vlan interfaces and 
subsequently remove the ``bogus'' link-local addresses without 
disturbing or crashing my system?


Trond.

- -- 
- ----------------------------------------------------------------------
Trond Endrestøl                          |   trond at fagskolen.gjovik.no
Patron of The Art of Computer Programming|   FreeBSD 6.1-S & Pine 4.64

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