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New Member

The IPv6 address command

Hi,

What's the difference between using the "ipv6 address" command with or without the eui-64 option?

Thanks!

4 REPLIES
Purple

Re: The IPv6 address command

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.

New Member

Re: The IPv6 address command

Thank you for your quick answer!

/Hakan

Silver

Re: The IPv6 address command

Hi ,

ipv6 address / eui-64

Configures an IPv6 address (and enables IPv6) on the interface

using a EUI-64 style "Interface ID" in the low order 64 bits.

(If the specified is greater than 64, the

prefix bits will have precedence over the Interface ID.)

check the below link

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122t/122t2/ipv6/ftipv6c.htm

Hope it helps you.

Thanks,

satish

New Member

Re: The IPv6 address command

Thank you for your quick answer!

/Hakan

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