Subject: Re: RFC vs. MIB internal metric contradiction

From: "Manral, Vishwas" <[email-masked]>
Date: Wed, 1 May 2002 10:02:59 -0400

Hi Magnus,

I do not know any existing scenarios where a metric value of 0 is used in
OSPF. However in ISIS a metric value of 0 is advertised in an interesting
application. Check the draft

http://www.ietf.org/internet-drafts/draft-ietf-isis-ext-lsp-frags-00.txt

It could be used in OSPF for a similar purpose, though I do not assume such
a thing would ever be required in OSPF.

Thanks,
Vishwas

-----Original Message-----
From: Magnus Andersson [mailto:[email-masked]]
Sent: Tuesday, April 30, 2002 6:18 PM
To: [email-masked]
Subject: RFC vs. MIB internal metric contradiction

After reading both RFC2328 and J.Moy(OSPF, Anatonomy of an Internet Routing
protocol) I understand that 0 is not a valid number for the metric field in
the router-LSA. However in the OSPFv2 MIB it seems that 0 is a valid value.
Are there other situations where we allow a metric of 0, or why does the
MIB say that we can use 0??

--  Note the OSPF Metric is defined as an unsigned value in the range
Metric ::= TEXTUAL-CONVENTION        STATUS       current        DESCRIPTION
           "The OSPF Internal Metric."
        SYNTAX       Integer32 (0..'FFFF'h)

RFC2328:
Interface output cost(s)
        The cost of sending a data packet on the interface, expressed in
        the link state metric.  This is advertised as the link cost for
        this interface in the router-LSA. The cost of an interface must
        be greater than zero.Interface output cost(s)
        The cost of sending a data packet on the interface, expressed in
        the link state metric.  This is advertised as the link cost for
        this interface in the router-LSA. The cost of an interface must
        be greater than zero.

OSPF, Anatonomy of an Internet Routing protocol:
        Each link also contains a Metric field. This field ranging from 1
        to 65535, indicates the relative cost of sending packets over the
        link.

---

From: "Naidu, Venkata" <[email-masked]>
Date: Wed, 1 May 2002 10:18:26 -0400

Vishwas & Magnus,

-> I do not know any existing scenarios where a metric value of
-> 0 is used in OSPF.

  OSPF loopback interfaces uses metric values of 0 (as per RFC2328).

Venkata.