What is IPv6 ? How it is different from IPv4 ? How many bits does an IPv6 adderss has ?
What is IPv6 ?
Internet Protocol version 6 (IPv6) is a network layer protocol for packet-switched internetworks. It is designated as the successor of IPv4, the current version of the Internet Protocol.
How it is different from IPv4 ?
Here are some of the points which makes it different than IPv4. The first one is a MUST. If you can tell any more than you will further impress the interviewer.
Larger address space
The main feature of IPv6 that is driving adoption today is the larger address space: addresses in IPv6 are 128 bits long versus 32 bits in IPv4.
The larger address space avoids the potential exhaustion of the IPv4 address space without the need for NAT and other devices that break the end-to-end nature of Internet traffic. The drawback of the large address size is that IPv6 is less efficient in bandwidth usage, and this may hurt regions where bandwidth is limited.
Stateless autoconfiguration of hosts
IPv6 hosts can be configured automatically when connected to a routed IPv6 network. When first connected to a network, a host sends a link-local multicast (broadcast) request for its configuration parameters; if configured suitably, routers respond to such a request with a router advertisement packet that contains network-layer configuration parameters.
If IPv6 autoconfiguration is not suitable, a host can use stateful autoconfiguration (DHCPv6) or be configured manually.
Stateless autoconfiguration is only suitable for hosts; routers must be configured manually or by other means.
Multicast
Multicast is part of the base protocol suite in IPv6. This is in opposition to IPv4, where multicast is optional.
Most environments do not currently have their network infrastructures configured to route multicast; that is — the link-scoped aspect of multicast will work but the site-scope, organization-scope and global-scope multicast will not be routed.
IPv6 does not have a link-local broadcast facility; the same effect can be achieved by multicasting to the all-hosts group (FF02::1).
The m6bone is catering for deployment of a global IPv6 Multicast network.
Jumbograms
In IPv4, packets are limited to 64 KiB of payload. When used between capable communication partners, IPv6 has support for packets over this limit, referred to as jumbograms. The use of jumbograms improves performance over high-throughput networks.
Faster routing
By using a simpler and more systematic header structure, IPv6 was supposed to improve the performance of routing. Recent advances in router technology, however, may have made this improvement obsolete[citation needed].
Network-layer security
IPsec, the protocol for IP network-layer encryption and authentication, is an integral part of the base protocol suite in IPv6; this is unlike IPv4, where it is optional (but usually implemented). IPsec, however, is not widely deployed except for securing traffic between IPv6 BGP routers.
Mobility
Unlike mobile IPv4, Mobile IPv6 (MIPv6) avoids triangular routing and is therefore as efficient as normal IPv6. This advantage is mostly hypothetical, as neither MIP nor MIPv6 are widely deployed today.
How many bits does an IPv6 adderss has ?
128 Bits - Here is an example of IPv6 address [2001:0db8:85a3:08d3:1319:8a2e:0370:7344]
I have seen many companies asking this question so make sure that you can speak a little more about IPv6 other than just the full form and bit size. By the way, Normal IPv4 addess has size 32 Bits.