Hi,
Here are my observations on the various forms of that command:
- Use the 'ipv6 enable' command to get IOS to configure an IPv6 link-local address on an interface without having to configure a global or site-local unicast address on it
- If a global or site-local unicast address is configured on an interface, a link-local address is automatically assigned to it. Note that the 'ipv6 enable' command remains in the config even if after an IPv6 address is configured.
- By default, the link-local address will use an interface ID in the modified EUI-64 format, derived from the MAC address of the interface.
- The only way to change the link-local address is to use the 'ipv6 address link-local' command. Note that you do not specify a prefix-length when using this command. If a prefix length is specified, the link-local option is not available. Once the link-local address of an interface is changed, the lower-order 64-bits of the new link-local address are considered the EUI-64 for that interface. Therefore, the use of the eui-64 option with the 'ipv6 address' command will now use this as the EUI-64 address, and will no longer use the MAC address of the interface to derive it.
- The configuration of a site-local or global unicast address has no effect on what the link-local address is ? it?s either formed using the modified EUI-64 format from its MAC address or is user-defined using the 'ipv6 address link-local' command.
- The 'ipv6 address /' command can be used to assign a complete IPv6 address to an interface. The specified address is treated as a complete address, including the interface ID component. Even if the interface ID is all zeros, it?s treated as an all-zero Interface ID ? the modified EUI-64 format is not applied at all.
- The 'ipv6 address / eui-64' command can be used to assign an IPv6 address to an interface, where the Interface ID is derived from the modified EUI-64 format of the interface?s MAC address (or the lower-order 64-bits of a manually assigned link-local address). Ideally, the specified prefix-length should be 64 bits; however, if the prefix length is greater than 64, the unspecified bits of the Interface ID are set to the corresponding bits from the modified EUI-64 address. If non-zero bits are specified in the portion of the address beyond the prefix-length, these are ignored when forming the final address. If the specified prefix-length is less than 64 bits, the bits between the prefix-length and bit 64 are set to zero.
Hope that helps...
Paresh
PS. Pls do remember to rate posts that help.
