Re: [Lsr] Methods to label the passive interfaces within ISIS

[Robert Raszuk <[e-mail]>]

Hi Tony,

I agree with you that essentially this is a link property (hence my earlier
hint towards 5029) so it makes it at least two of us recommending direction
towards 5029 now ;)

While we are at this perhaps it would be also useful to be able to
differentiate reachability on stub links vs virtual local interfaces. Today
in some implementations they are advertised after marking them as passive
int.

Thx
R.


On Fri, Jan 10, 2020, 08:26 <[e-mail]> wrote:

>
> Hi Aijun,
>
>
> For the link attributes that defined in RFC5029, as that stated in
> https://tools.ietf.org/html/rfc5029#section-2, this sub-TLV is included
> in the TLV 22(Extended IS Reachability).
> As I read the IANA code point
> https://www.iana.org/assignments/isis-tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-22-23-25-141-222-223
> , it notes this sub-TLV can be included in all of these TLVs
> (22,23,25,141,222,223).
>
> But, when the interface is configured as passive/stub, it seems that the
> above TLVs will not be advertised, because there is no IS neighbor on this
> passive link.
>
>
>
> Fair point. Given that there is an IP address and prefix on that link, it
> would be very reasonable to advertise the Extended IP Reachability TLV
> (135). We would then need to make the link attributes sub-TLV applicable to
> this TLV (and it’s MT brother).
>
>
> TLV 141 “Inter-AS reachability information” seems be one appropriate TLV
> to include this sub-TLV, but it requires the IS-IS TE deployment, and is
> not suitable for describing the passive/stub link on edge router.
>
> In summary, it seems put this attribute into the “Prefix Attribute Flags”
> sub-TLV which can be included in TLV 135,235,236 and 237 (Extended IP
> reachability, MT IP. Reach, IPv6 IP. Reach, and MT IPv6 IP. Reach TLVs) is
> more applicable?
>
>
>
> It would seem to me that what you’re describing is an attribute of a link,
> not of a prefix, thus I would favor it remaining a link attribute.
>
> But that’s just me.  :-)
>
> Tony
>
>