| IPv4 | IPv6 |
| Addresses are 32 bits (4 bytes) in length. | Addresses are 128 bits (16 bytes) in length |
| Address (A) resource records in DNS to map host names to IPv4 addresses. | Address (AAAA) resource records in DNS to map host names to IPv6 addresses. |
| Pointer (PTR) resource records in the IN-ADDR.ARPA DNS domain to map IPv4 addresses to host names. | Pointer (PTR) resource records in the IP6.ARPA DNS domain to map IPv6 addresses to host names. |
| IPSec is optional and should be supported externally | IPSec support is not optional |
| Header does not identify packet flow for QoS handling by routers | Header contains Flow Label field, which Identifies packet flow for QoS handling by router. |
| Both routers and the sending host fragment packets. | Routers do not support packet fragmentation. Sending host fragments packets |
| Header includes a checksum. | Header does not include a checksum. |
| Header includes options. | Optional data is supported as extension headers. |
| ARP uses broadcast ARP request to resolve IP to MAC/Hardware address. | Multicast Neighbor Solicitation messages resolve IP addresses to MAC addresses. |
| Internet Group Management Protocol (IGMP) manages membership in local subnet groups. | Multicast Listener Discovery (MLD) messages manage membership in local subnet groups. |
| Broadcast addresses are used to send traffic to all nodes on a subnet. | IPv6 uses a link-local scope all-nodes multicast address. |
| Configured either manually or through DHCP. | Does not require manual configuration or DHCP. |
| Must support a 576-byte packet size (possibly fragmented). | Must support a 1280-byte packet size (without fragmentation). |
