1.1.d [ii] IPv4 options, IPv6 extension headers
Main/ Regular IPv6 Header IPv6 Extension Headers
The main IPv6 header is equivalent to the basic IPv4 one despite some field differences that are the result of lessons learned from operating IPv4.
Extension headers are an intrinsic part of the IPv6 protocol and they support some basic functions and certain services. The following is a list of situations where EHs are commonly used:
● Hop-by-Hop EH is used for the support of Jumbo-grams or, with the Router Alert option, it is an integral part in the operation of Multicast Listener Discovery (MLD). Router Alert is an integral part in the operations of IPv6 Multicast through MLD) and RSVP for IPv6.
● Destination EH is used in IPv6 Mobility as well as support of certain applications.
● Routing EH is used in IPv6 Mobility and in Source Routing. It may be necessary to disable ipv6 source routing using ipv6 source-route command on routers to protect against DDoS.
● Fragmentation EH is critical in support of communication using fragmented packets (in IPv6, the traffic source must do fragmentation-routers do not perform fragmentation of the packets they forward)
● Mobility EH is used in support of Mobile IPv6 service
● Authentication EH is similar in format and use to the IPv4 authentication header
● Encapsulating Security Payload EH is similar in format and use to the IPv4 ESP header. All information following the Encapsulating Security Header (ESH) is encrypted and obfuscated and for that reason, it is invisible to intermediary network devices.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1049-1060). . Kindle Edition.