What's the purpose when we config ipv6 address for an interface with 128bit mask

[rock830906]

What's the purpose when we config ipv6 address for an interface with 128bit mask?

Thanks

[Karsten Iwen · Accepted solution]

If you configure a loopback-interface you can use a /128 there.

"Normal" interfaces should always use /64 (RFC 4291) while on router-to-router-links you can use a /127 (RFC 6164).

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[rock830906]

But it's able to configure any mask from 1 to 128 on cisco router. Is it a bug or wrong configuration?

[Karsten Iwen]

There are many things in IOS that can be configured because it's allowed to configure it. But not everything that can be configured should be configured ...

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[rock830906]

Thank you, karsten.iwen