01-20-2004 01:26 PM - edited 03-02-2019 01:02 PM
Hello.
What is the maximum number of AS #s that can be included in the AS_PATH Attribute of a particular route ?
In the RFC it states:
"Total Path Attribute Length: This 2-octet unsigned integer indicates the total length of the Path Attributes field in octets."
So it's 512 ?
Thanks.
-Rob
01-20-2004 07:10 PM
The "Total Path Attribute Length" you are referring to is the the length of the sum of all the path attributes for a specific NLRI, not only the AS PATH length.
RFC1771 makes the following statement though:
+++++++++++++++++++++++++++++++++++++++++++++++++
The path segment length is a 1-octet long field containing the number of ASs in the path segment value field.
+++++++++++++++++++++++++++++++++++++++++++++++++
This would limit the number of AS in the ASPATH to 255.
Hope this helps,
01-21-2004 04:23 PM
That's not quite true. It is possible to have more than one AS path segment triple
Cheers,
Paresh.
01-21-2004 10:03 PM
Paresh,
I should have said the limit is 255 ASs given that you don't have an AS_SET. I don't believe the IOS implementation will create an additional AS_SEQUENCE triple to allow more than 255 ASs.
That being said, this is a theorical discussion since the maximum ASPATH length seen on the Internet is more in the order of 15 to 20.
Thanks for keeping me honest.
01-22-2004 03:22 PM
Yeah, I can't imagine that I would want a route with an AS_PATH length of more than 255 in my routing table !!
Paresh.
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