18.3.1 Internet Protocol Version 6 (IPv6)

<Structure of this section>

(1) IPv6 Packet Format

The format and settings of IPv6 packets sent by the Switch conforms to RFC 2460. The following figure describes the format of an IPv6 packet.

Figure 18-21: IPv6 Packet Format

(2) IPv6 packet header validity checking

The 40-octet IPv6 header contains eight fields and two addresses. The following figure shows the format of an IPv6 header.

Figure 18-22: IPv6 format of the heading

The Switch checks the validity of the IPv6 headers in IPv6 packets when IP packets are received. The following table describes the IPv6 packet header items that are checked.

Table 18-4 Items checked in IPv6 packet header
IPv6 packet header field	Check item	When a check error occurs Packet processing	Whether to send an ICMPv6 message for a discarded packet
Version	Be version = 6	Discarded	Do not send
Traffic class	Not checked.	-	-
Flow label	Not checked.	-	-
Payload length	Compare with the packet length. If the payload length is greater than the packet length, the packet is discarded.	Discarded	Do not send
Payload length	Compare with the packet length. The payload length must be less than the packet length.	The payload length is removed from the end of the packet.	Do not send
Next header	Not checked.	-	-
Hop limit	The hop limit of the received packets directed to the local device is not checked.	-	-
Hop limit	For the hop limit of the packets to be forwarded: Hop limit - 1 > 0	Discarded	Send^#
Source address	The following conditions must be satisfied: The address is not a link-local address. The address is not a multicast address.	Discarded	Do not send
Destination address	The following conditions must be satisfied: The address is not the loopback address. The interface ID is not 0 (except for the unspecified address).	Discarded	Do not send

Legend:-: Not applicable

#: An ICMPv6 Time Exceeded message is sent.

(3) IPv6 Extension Header Supported

The following table describes the IPv6 extension headers supported by the Switch.

Table 18-5 Items in IPv6 extension headers
IPv6 extension header	Type of IPv6 packet
IPv6 extension header	With the departing station of the equipment Packet to be	When the Switch arrives at the station Packet to be added*1	Relay by the Switch Packet
Hop-by-Hop Options Header	OK	OK	OK^#2
Routing Header	OK	OK	-
Fragment Header	OK	OK	-
Authentication Header	NG	NG	-
Encapsulating Security Payload Header	NG	NG	-
Destination Options Header	OK	OK	-

(Legend) OK: Supported NG: Not supported-: No header processing

Note #1

If a packet that reaches the Switch satisfies the following conditions, the packet is discarded:

- Nine or more extension headers are set.

- Nine or more options are set in one extension header.

Note #2

If the packet to be forwarded by the Switch satisfies the following condition, the packet is discarded:

- Nine or more options are set in the Hop-by-Hop Options header.