- #CONVERT MAC ADDRESS TO IPV6 LINK LOCAL INSTALL#
- #CONVERT MAC ADDRESS TO IPV6 LINK LOCAL MANUAL#
- #CONVERT MAC ADDRESS TO IPV6 LINK LOCAL MAC#
The complete Tcpdump command which uses the second interface card on the host and creates a new *.pcap every day looks like that: I am storing the logfiles in a subfolder under /var/log: That is, the following Tcpdump filter captures only DAD messages: The DAD messages can entirely be classified since they are “Neighbor Solicitation” ICMPv6 messages of type 135 ( RFC 4861) and are always sent from a source address of “::” ( RFC 4862). That is: It is only used for the passive sniffing on the network. For the subsequent analysis, the stored *.pcap file is read into a textfile which can then be analysed using grep, etc.įor the capturing of IPv6 packets I recommend to use a second hardware interface on the Linux host which does not participate at layer 3 at all, i.e., has no IPv6 addresses: I am dividing my method in two sections: At first, a Tcpdump runs in the background in order to store all DAD messages in a *.pcap file. The Tcpdump line for the same DAD message looks like that: The message has ICMPv6 type 135 and a “Target Address” of its tentative link-local IPv6 address (fe80::…):
#CONVERT MAC ADDRESS TO IPV6 LINK LOCAL MAC#
The Ethernet frame is sent to an IPv6 multicast address (beginning with 33:33:) with a source MAC address of the IPv6 node, in this case an Apple device. Here is a Wireshark screenshot of a DAD message. That is: Our sniffing Linux host will receive all DAD messages that appear on the local network. (Remember: There are no broadcasts anymore with IPv6.) However, since common layer 2 switches do not maintain multicast listener groups, they simply forward these messages to all switchports. This ICMPv6 neighbor solicitation message is sent to the solicited-node multicast address of the target address.
#CONVERT MAC ADDRESS TO IPV6 LINK LOCAL MANUAL#
Duplicate Address DetectionĮvery IPv6 node on the network that wants to register a new IPv6 address must run the duplicate address detection (DAD) method in order to find out whether this IPv6 address is already used by another IPv6 node: “ Duplicate Address Detection MUST be performed on all unicast addresses prior to assigning them to an interface, regardless of whether they are obtained through stateless autoconfiguration, DHCPv6, or manual configuration, ”, RFC 4862, Section 5.4. Since we had no layer 2 switches that support first-hop security services such as neighbor discovery monitor or router advertisement guard, the idea was to use a host on the local network to sniff and “search” for new IPv6 addresses and their correspondent MAC addresses. One of the first questions in this scenario was: How can we know which device had which IPv6 address at a given time? How can we trace back which device (user) has done some malicious actions when we only see many different “privacy extended” IPv6 addresses in the firewall log without any MAC addresses? In this way, many users and clients will operate with IPv6 without touching the productive LAN. We decided to activate IPv6 on the guest/ BYOD Wifi.
![convert mac address to ipv6 link local convert mac address to ipv6 link local](https://cdn.networkacademy.io/sites/default/files/inline-images/ipv6-link-local-address-example.png)
In this blog post I will present a use case for storing these bindings, the concept of the DAD messages, a Tcpdump script for doing this job, and the disadvantages and alternatives of this method.Ī customer wanted to test IPv6 in order to achieve knowledge for the IT admins.
![convert mac address to ipv6 link local convert mac address to ipv6 link local](https://ben.akrin.com/wp-content/uploads/2020/11/IMG_0826.jpg)
This can be done with a small Tcpdump script on a dedicated Ethernet interface of a Linux host.
#CONVERT MAC ADDRESS TO IPV6 LINK LOCAL INSTALL#
The mapping of “identity to IP” is not done automatically somewhere.Ī simple way to overcome this issue is to install a service that captures Duplicate Address Detection (DAD) messages from all clients on the subnet in order to store the bindings of MAC and IPv6 addresses. That is, a subsequent analysis of network behaviour corresponding to concrete IPv6 addresses and their client machines is not possible anymore. In the IPv6 world, if SLAAC (autoconfiguration) is used, no network or security device per se stores the binding between the MAC (layer 2) and the IPv6 (layer 3) addresses from the clients. In the legacy IPv4 world, the DHCP server allocates IPv4 addresses and thereby stores the MAC addresses of the clients.