Re: Looking for information on IGP choices in dual-stack networks

[Mark Tinka <mark.tinka () seacom mu>]

On 10/Jun/15 21:56, Robert Drake wrote:
> When we first were moving to IPv6 in the core network we evaluated
> IS-IS because it was what we were using for IPv4 and we would have
> preferred to run a single protocol for both.  We had problems with
> running a mix of routers where some supported IPv6 and others did
> not.  From what I recall, if any router did not support IPv6 then it
> wouldn't connect to a router running v6 and v4.
>
> It's possible these were bugs and they were worked out later or just a
> messed up design in the lab, but we also like the idea of keeping IPv4
> and IPv6 away from each other so if one is broken the other one might
> still work.

Someone may have already mentioned this, but you hit that issue because
you were probably running ST (Single Topology) IS-IS.

IS-IS supports MT (Multi Topology) which allows you to have incongruent
IP stacks on a link, i.e., IPv4 on one end + IPv4/IPv6 on another. As
the majority of strategies to implement IPv6 will be in this manner,
always recommended to run IS-IS in MT mode.

Unless you were implementing IS-IS before MT was supported in code.

Mark.