If a networking device has attained Link Local Address and attains a Link Local Address - say - 169.254.111.135. Now if DHCP got enabled in the device and it acquires an IP from DHCP server in network - should the device give away Link Local Address?
What is the ideal situation in such a case for the device to do?
Is defined on RFC 3927 section 1.9:
If a host finds that an interface that was previously configured with an IPv4 Link-Local address now has an operable routable address available, the host MUST use the routable address when initiating new communications, and MUST cease dvertising the availability of the IPv4 Link-Local address through whatever mechanisms that address had been made known to others. The host SHOULD continue to use the IPv4 Link-Local address for communications already underway, and MAY continue to accept new communications addressed to the IPv4 Link-Local address. Ways in which an operable routable address might become available on an interface include:
- Manual configuration
- Address assignment through DHCP
- Roaming of the host to a network on which a previously assigned address becomes operable
So yes, if the device gets assigned a DHCP address then Link Local one should be dropped. Check https://www.rfc-editor.org/rfc/rfc3927#section-1.9
For IPv4, it is usual to drop the Link Local Address when an IP address is obtained by another means. Once you have attained a different IP address the Link Local Address doesn't have much use.
For IPv6, the Link Local Address is retained.
