DHCPv6 Relay Remote-ID Option

Available in ExtremeXOS 15.5, the remote-id option is added to the relay forward IPv6 message, if the specific VLAN (Virtual LAN) has only the link local IPv6 address. This remote-id is added to all the request packets received from the client on that VLAN, if it is configured or not on the VLAN. The remoteID option added to the packet after the relay message header has the following format, as defined in RFC 4649:

If the remote-id is configured through the CLI on a specified VLAN, it can have either a user defined value, or the system-name. If the user does not configure the value or marks “none” as the remote-id, the switch MAC address will be used as the remote-id. The value of the remote-id present in the packet will have the following format:vlan_port_<remoteId, where remoteId will be either the configured string, or the system name or the switch MAC address. The Enterprise number field will be populated with the Extreme Networks enterprise number, “1916”.

The remote-id is added to the packets on a specified VLAN, only if:

IPv6 bootprelay is enabled on the VLAN.
rhe vlan has only the link local address.

Once a relay agent receives one of the following messages from the client or relay agent, the relay agent will verify if the specific interface has only the link local address:

DHCPV6_SOLICIT
DHCPV6_REQUEST
DHCPV6_CONFIRM
DHCPV6_RENEW
DHCPV6_REBIND
DHCPV6_RELEASE
DHCPV6_DECLINE
DHCPV6_INFORMATION_REQUEST
DHCPV6_RELAY_FORW
DHCPV6_LEASEQUERY

If so, it verifies if the specific VLAN has a remote-id configured. If a remote-id is present, it is added to the packet along with the VLAN and port, in the format mentioned above. If it is not configured, the default (switch MAC address) will be added as the remote id, along with the VLAN and port.

On the reverse path, if it receives any of the following messages from the server or any other relay agent, and if the interface has only a link local address, it will verify for the presence of remote-id in the packet:

DHCPV6_ADVERTISE
DHCPV6_REPLY
DHCPV6_RECONFIGURE
DHCPV6_RELAY_FORW
DHCPV6_LEASEQUERY_REPLY

If it is not present, the agent will check for the interface-id. If one of these is present, it will verify if the value matches the local configuration. If it matches, after removing the remote-id and/or interface-id, the packet will be forwarded to the respective client. If the remote-id is present in the packet, and it does not match the configured value, the packet will be dropped. If none of them are present, the packet will be forwarded to the client, based on the IPv6 address of the VLAN.

Published March 2020prev | next

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