Neighbor Solicitation Address Calculator

About this interactive

When a host needs a neighbor's MAC address it cannot broadcast, so it sends a neighbor solicitation to the neighbor's solicited-node group: ff02::1:ff followed by the last 24 bits of the neighbor's address. At layer 2 that group becomes the MAC address 33:33 followed by the group's last 32 bits, so only devices that joined it take the frame in. The host sends from its own address and MAC, and the neighbor answers with a neighbor advertisement sent straight back to them: unicast. Duplicate address detection uses the same message, with two differences. The host is asking about its own new address, so the destination is that address's solicited-node group, and it cannot use the address yet, so the source is the unspecified address, ::. If nobody answers, the address is free. For example, fe80::21c:42ff:fe00:9 would be checked at ff02::1:ff00:9, in a frame to 33:33:ff:00:00:09. Seven of the sixteen questions are drawn each run. Any you miss shows the answer and how to work it out.

What you'll learn

Work out the source and destination addresses, IPv6 and MAC, of a neighbor solicitation and of the neighbor advertisement that answers it
Work out the addresses of a duplicate address detection check: the unspecified source, the solicited-node destination and its 33:33 MAC

Aligned to

Cisco CCNA

1.9 Describe IPv6 address types

CompTIA Network+

3.4 Given a scenario, implement IPv4 and IPv6 network services

Key terms

Neighbor Solicitation: An ICMPv6 message used in IPv6 Neighbor Discovery to request the MAC address corresponding to a specific IPv6 address or to verify that a neighbor is still reachable. Neighbor Solicitation is also used during Duplicate Address Detection to check that a new IPv6 address is unique.
Neighbor Advertisement: An ICMPv6 message sent in response to a Neighbor Solicitation, providing the MAC address corresponding to a requested IPv6 address as part of the Neighbor Discovery Protocol. NA messages are also sent unsolicited to announce link-layer address changes.
Solicited-Node Multicast Address: A special IPv6 multicast address in the FF02::1:FF00:0/104 range that is derived from the last 24 bits of a device's IPv6 address, used by Neighbor Discovery to efficiently perform address resolution without broadcasting to all hosts. Instead of flooding all devices the way ARP does in IPv4, NDP sends solicitations only to the small group of devices sharing those same 24 bits.
Duplicate Address Detection: An IPv6 mechanism that verifies a newly assigned address is unique on the link before it is used for communication. A device sends a Neighbor Solicitation for its tentative address; if no response is received, the address is confirmed unique and assigned.
Unspecified Address: The IPv6 address ::/128 (all zeros), used to indicate the absence of an address, typically before a device has been assigned one.

Topics

Ipv6 Ndp Neighbor Solicitation Solicited Node Duplicate Address Detection Interactive Calculation

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