From: CCIE KH49279 (ccie_lab@inetiq.com)
Date: Tue Feb 21 2006 - 14:24:21 GMT-3
Short answer: I do not believe the connection is dropped due to bad updates,
but there will be error notifications sent back to the sender.
Long Answer:
According to RFC 4271 the following error subcodes exist to protect against
the well-known attribute that is either not recognized or missing. Further
more the RFC specifically states:
"BGP implementations MUST recognize all well-known attributes. Some of
these attributes are mandatory and MUST be included in every UPDATE message
that contains NLRI."
In addition, (see - beginning page 31 of RFC 4271) BGP will specifically
issue error messages in response to an UPDATE Message notification error
back to the sender.
I suspect each implementation could vary, but I see no point in allowing
such a condition to pass through with the assumption it is valid.
UPDATE Message Error subcodes:
2 - Unrecognized Well-known Attribute.
3 - Missing Well-known Attribute.
I believe if the well-known mandatory attribute is not present the
implementation will reject the update and send the one of the above
subcodes, and squash the update.
Since you are asking the question, I am assuming you understand the basic
principal of the four attribute types:
1. Well-Known Mandatory
2. Well-Known discretionary
3. Optional transitive
4. Optional non-transitive
Please let the list know if you find out differently, but I suspect you will
not find such an implementation to exists that has not been purposely built
to work around such an error condition.
Short answer: I do not believe the connection is dropped due to bad updates,
but there will be error notifications sent back to the sender.
HTH,
Wayne
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Maneesh Chawla
Sent: Tuesday, February 21, 2006 1:19 AM
To: ccielab@groupstudy.com
Subject: BGP : Madatory attributes
Hi All,
What should happen to a route if it is received without one of the
mandatory attributes(say, AS). Should the connection be dropped ?
Thanks
Maneesh
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