Vahid,
Section 2.1.1.2 of the IS-IS Extensions for Segment
Routing<https://tools.ietf.org/html/draft-ietf-isis-segment-routing-extensions-23>
draft defines N-Flag in the Prefix-SID Sub-TLV as following (the relevant text
is highlighted):
N-Flag: Node-SID flag. If set, then the Prefix-SID refers to
the router identified by the prefix. Typically, the N-Flag is
set on Prefix-SIDs attached to a router loopback address. The
N-Flag is set when the Prefix-SID is a Node-SID as described in
[RFC8402<https://tools.ietf.org/html/rfc8402>].
An RF C 8402 states in Section 3.2:
An IGP Node-SID MUST NOT be associated with a prefix that is owned by
more than one router within the same routing domain.
Therefore, the answer to your first question “What happens if I don’t implement
these rules in network?” is simple: Your implementation violates a mandatory
requirement of the Segment Routing architecture.
Regards,
Sasha
Office: +972-39266302
Cell: +972-549266302
Email: [email protected]
-----Original Message-----
From: spring <[email protected]> On Behalf Of vahid tavajjohi
Sent: Saturday, April 13, 2019 7:39 AM
To: [email protected]
Subject: [spring] Anycast-SID
Hi SPRING WG,
I have a question about Anycast-SID.
1- In RFC 8402 section 3.2, it mentioned that “Node-SID MUST NOT be associated
with a prefix that is owned by more than one router within the same routing
domain”. Also, in section 3.3, it mentioned that “ An IGP-Anycast segment MUST
NOT reference a particular node”.
2- Also, we have N-Flag “isis-segment-routing-extensions-23” that indicates
whether Prefix-SID related to a node or not.
My questions are:
1- What happens if I don’t implement these rules in network?
2- What happens if I set anycast-sid on multiple nodes, but I don’t set "n-flag
clear” under loopback configuration?
3- Why "IGP-Anycast segment MUST NOT reference a particular node” ?
Best Regards,
Vahid
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