H3C Technologies H3C S5560 Series Switches - Manual (Page 213)

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H3C implementation of Option 18 and Option 37
Option 18 for DHCPv6 snooping
Option 18, also called the interface-ID option, is used by the DHCPv6 relay agent to determine the
interface to use to forward RELAY-REPLY message.
In H3C implementation, the DHCPv6 snooping device adds Option 18 to the received DHCPv6 request
message before forwarding it to the DHCPv6 server. The server then assigns IP address to the client
based on the client information in Option 18.
Figure 79 Option 18 format
Figure 79 shows the Option 18 format, which includes the following fields:
• Option code—Option code.
• Option length—Size of the option data.
• Port index—Port that receives the DHCPv6 request from the client.
• VLAN ID—ID of the outer VLAN.
• Second VLAN ID—ID of the inner VLAN.
• DUID—DUID of the DHCPv6 client.
NOTE:
The Second VLAN ID field is optional. If the received DHCPv6 request does not contain a second VLAN,
Option 18 also does not contain it.
DHCPv6 snooping support for Option 37
Option 37, also called the remote-ID option, is used to identify the client.
In H3C implementation, the DHCPv6 snooping device adds Option 37 to the received DHCPv6 request
message before forwarding it to the DHCPv6 server. This option provides client information about
address allocation.