From: crl (cisco@xxxxxxxxxxxx)
Date: Tue May 22 2001 - 10:52:50 GMT-3
There's not a lot of information in the archives about Lab 18 yet.
Looking at section Three, Task One, Number 4 it asks to have R6 prefer
routes learned from one router over the other, but without making
changes to the BGP configuration. My thought was to tinker with the
router ID, since all other things would be equal.
So, to accomplish this task, I added a loopback to R5 with an IP lower
than R3's RID and reset the BGP sessions. This did not work. Checking
the provided solutions didn't help, since I can't find anything in there
that would accomplish the required task.
Anyhow, I was reading the "Troubleshooting BGP" PDF from the Australia
Networkers conference, and on page 65 the following phrase is included:
The "oldest" external is the bestpath.
All other attributes are the same
Stability enhancement!
This seems to be saying that the RID is not used as the "tiebreaker",
that BGP will prefer whatever path it has "known" longer. I can't find
this new behaviour documented as a "new feature" or anything under
release notes on the doc CD or Cisco's website. Can anybody provide more
information about this as it would imply that the path selection process
as documented on the CD and in Halabi is slightly incorrect.
BGP Path Selection Process on the doc CD:
http://127.0.0.1:8080/cc/td/doc/product/software/ios120/12cgcr/np1_c/1cp
rt1/1cbgp.htm#xtocid87022
The PDF with the statement about the "stability enhancement" - page 65:
http://www.cisco.com/networkers/au/presentations/ccie/TroubleshootingBGP
.pdf
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