Subject: [mpls] LDP Discovery

From: Sundar Selveraj <[email-masked]>
Date: Thu, 27 May 2010 12:15:28 +0530

I have a question on LDP Basic Discovery Process.
 Hi All,

        Am looking out for some clarification on LDP Discovery process.

        LDP Hellos are sent to All routers Multicast Address (224.0.0.2).So
any LDP capable router on recieveing this packet reaches Full neighborship.

          I had a strange (infact a misconfiguration) setup, wherein I had
address configured incorrectly. For example, address on a different subnet
over the directly connected interfaces.(1.1.1.1/24 <----> 1.1.2.1/24)

        I could still see the adjacency coming up. In other words, we are
not doing a source-address check.I went through some juniper documentation
on LDP and understood that they have a knob (CLI) to enable/disable
source-address.

        I am just curious to understand why was the source-address check not
mentioned in the RFC.

        Is it fine that the neighborship gets established inspite of having
a misconfiguration? If the answer to the question is yes, can you share your
thoughts on why Juniper could have included the source-address check?

Regards
Somasundaram

---

From: Eric Gray <[email-masked]>
Date: Tue, 1 Jun 2010 11:45:25 -0400

Somasundaram,

One area of discussion that is not allowed on this mailing list is discussion
of why a particular vendor does or does not do something in the way that
the standard(s) define(s).

Please address that part of this question to appropriate product support.

As for the rest of the question, it is not always possible to address issues
with misconfiguration in protocol specification and - unless a particular
misconfiguration is likely to produce drastic pathological behavior in a
network - it is usually not worth the trouble to try to identify all of the
(probably very many) ways that devices may be misconfigured.  In my
experience, this is particularly true when the major effect of such an
error in configuration is to embarras the vendor(s) that allowed it in
the first place.

--
Eric
________________________________
From: [email-masked] [[email-masked]] On Behalf Of Sundar Selveraj [[email-masked]]
Sent: Thursday, May 27, 2010 8:45 AM
To: [email-masked]
Subject: [mpls] LDP Discovery

        LDP Hellos are sent to All routers Multicast Address (224.0.0.2).So any LDP capable router on recieveing this packet reaches Full neighborship.

          I had a strange (infact a misconfiguration) setup, wherein I had address configured incorrectly. For example, address on a different subnet over the directly connected interfaces.(1.1.1.1/24<http://1.1.1.1/24> <----> 1.1.2.1/24<http://1.1.2.1/24>)

        I could still see the adjacency coming up. In other words, we are not doing a source-address check.I went through some juniper documentation on LDP and understood that they have a knob (CLI) to enable/disable source-address.

        I am just curious to understand why was the source-address check not mentioned in the RFC.

        Is it fine that the neighborship gets established inspite of having a misconfiguration? If the answer to the question is yes, can you share your thoughts on why Juniper could have included the source-address check?

Regards
Somasundaram

---

From: "Dutta, Pranjal K (Pranjal)" <[email-masked]>
Date: Tue, 1 Jun 2010 22:18:30 +0530

I would second to Eric on this. The question raised is very 
implementation specific and such guidelines can't be specified 
in RFCs. In that way there could be umpteen areas which are beyond 
the purview of an IETF standard document.

Thanks,
Pranjal

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Eric Gray
Sent: Tuesday, June 01, 2010 8:45 AM
To: Sundar Selveraj; [email-masked]
Subject: Re: [mpls] LDP Discovery

Somasundaram,

Regards
Somasundaram
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