To enable dynamic measurements for the interface, the user must configure a link measurement template and enable the test protocol using the ipv4 or ipv6 command. The link measurement template does not include interface-specific requirements, such as the IP protocol encapsulating the test packet or IP source and destination addressing. It is possible to enable the IPv4 or IPv6 protocol under the dynamic>twamp-light context without including any source or destination information.
When the IPv4 protocol is enabled with no addressing configured, the source address is automatically assigned to the primary IPv4 address of the IP interface. The destination address is automatically assigned if the primary IPv4 address has a prefix length of 30 or 31. In other cases, such as shorter prefix lengths or unnumbered interfaces, the destination address cannot be resolved and must be configured manually. The source and destination commands take precedence over the auto-assigned addressing; the IPv4 addresses must be unicast.
When the IPv6 protocol is enabled without any source and destination address configuration, the IPv6 addresses are not automatically assigned. The source and destination address must be configured. The source and destination can be globally routable unicast addresses of the link identifying the directly connected peers or the link local addresses connecting the peers. The link local address must follow the format fe80::/64 as described in RFC 4291, IP Version 6 Addressing Architecture.
Auto-assigned addressing is not updated for operationally up interface delay tests when the IP addressing associated with that interface is changed. Two options are suggested to update the auto-assigned addressing in this case:
administratively disable and enable the protocol used for the interface delay test
disable and enable the IP interface under which the IP address has changed
TWAMP Light test packets consult the routing table to determine how to reach the destination. The test should be configured to use local IP interface source and directly connected IP peer interface destination addressing to ensure the packet egresses and returns over the same IP interface. The destination must be reachable from the IP interface where the interface delay test is configured. Using indirect IP addressing, such as unnumbered interfaces, does not guarantee that the measurement is reporting the delay for the expected interface.
Only one protocol, IPv4 or IPv6, can be enabled for an interface delay test at any time.
Interfaces defined as loopback do not support interface delay tests and are an invalid interface type. The configuration exists under these interfaces, but a detectable transmission error prevents the sending of packets.
The system interface does not support interface delay tests and the configuration is hidden.