Transcript How The Magic Trick Works - CHI-NOG

IPv6: Passing on Lessons Learned
from My Journey
Denise “Fish” Fishburne
Customer Proof of Concept Team Lead
CCIE #2639, CCDE 2009:0014
BRKARC-2002
Agenda
• Show a Magic Trick
• Explain How the Magic Trick works
• Resolving the destination MAC
The Magic Trick
The Magic Trick
How The
Magic Trick Works
How the Magic Trick Works
FF02::5
FF02::5
FE80::2237:6ff:fecf:67e4
FE80::2237:6ff:fecf:67e4
FF02::5
FE80::5a0a:20ff:feeb:91e4
FE80::5a0a:20ff:feeb:91e4
How the Magic Trick Works
FF02::5
How the Magic Trick Works
How the Magic Trick Works
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Multicast
Local: They are local to the wire they are on.
Common interest:
If a router wants to participate in EIGRP, it already knows the local multicast address (IPv4/IPv6) to start to
listen to and the corresponding MAC address.
Join:
“Join” just by just deciding to listen to a local multicast address and then, by extension,
to the corresponding MAC address for that multicast IP address.
Exists in IPv4 & IPv6
How the Magic Trick Works
FE80::2237:6ff:fecf:67e4
FE80::5a0a:20ff:feeb:91e4
How the Magic Trick Works
FE80::2237:6ff:fecf:67e4
FE80::5a0a:20ff:feeb:91e4
How the Magic Trick Works
How the Magic Trick Works
Puzzle Piece: Link-Local Address
“In the Internet Protocol Version 6 (IPv6), the address block fe80::/10 has been reserved for
link-local unicast addressing. The actual link local addresses are assigned with the prefix
fe80::/64. They may be assigned by automatic (stateless) or stateful (e.g. manual) mechanisms.
Unlike IPv4, IPv6 requires a link-local address to be assigned to every network interface on
which the IPv6 protocol is enabled, even when one or more routable addresses are also
assigned. Consequently, IPv6 hosts usually have more than one IPv6 address assigned to each
of their IPv6-enabled network interfaces.
The link-local address is required for IPv6 sublayer operations of the Neighbor Discovery
Protocol, as well as for some other IPv6-based protocols, like DHCPv6.”
Wikipedia
https://en.wikipedia.org/wiki/Link-local_address#IPv6
Resolving Destination
MAC Address
IPv4 w/ Broadcasts
10.10.10.2
How Does this Work
without Broadcast
and ARP?
Resolving Destination MAC Address
Resolving Destination MAC Address
Resolving Destination MAC Address
Solicited-Node
Multicast
Solicited-Node Multicast
Snippets from RFC4291 section 2.7
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A node is required to compute and join (on the appropriate interface) the associated
solicited-node multicast addresses for all unicast and anycast addresses that have been
configured for the node's interfaces (manually or automatically).
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Solicited-Node Address: FF02:0:0:0:0:1:FFXX:XXXX
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Solicited-node multicast address are computed as a function of a node's unicast and
anycast addresses.
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For example, the solicited-node multicast address corresponding to the IPv6 address
4037::01:800:200E:8C6C is FF02::1:FF0E:8C6C.
Solicited-Node Multicast
Solicited-Node Address: FF02:0:0:0:0:1:FFXX:XXXX
Solicited-Node Multicast
Snippets from RFC4291 section 2.7
•
Solicited-node multicast address are computed as a function of a node's unicast and
anycast addresses.
•
For example, the solicited-node multicast address corresponding to the IPv6 address
4037::01:800:200E:8C6C is FF02::1:FF0E:8C6C.
Solicited-Node Multicast
Solicited-Node Multicast
Solicited-Node Multicast
Neighbor
Discovery Protocol
Neighbor Discovery Protocol
Neighbor Discovery Protocol