From: ccie2be (ccie2be@nyc.rr.com)
Date: Tue Jul 05 2005 - 18:01:47 GMT-3
You're confusing 2 different concepts.
The BGP path selection algorithm decides which bgp route is best when
there's multiple paths to choose from.
The best path chosen is the one that gets entered into the route table.
If the best bgp path was learned via ibgp, then the AD of that route is 200
when it's entered into the route table.
If the best bgp path was learned via ebgp, then the AD of that route is 20
when it's entered into the route table.
So, the sequence of events is this:
1st, BGP chooses the best path. Step 9 compares ebgp to ibgp and selects
ebgp routes.
2nd, the best bgp path selected is entered into the route.
HTH, Tim
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
cciein2006@yahoo.com
Sent: Tuesday, July 05, 2005 4:23 PM
To: ccielab@groupstudy.com
Subject: BGP path selection process
Hello all,
I have some confusion regarding the path selection proces in BGP. According
to cisco documentation, step nine is:
"9. Prefer the external BGP (eBGP) path over the iBGP path."
Shouldn't that be step number 1? Considering the administrative distance of
eBGP is 20 and iBGP is 200, wouldn't the router immediately choose the eBGP
path even before looking at weight, local preference, etc...
Here is the Cisco link:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuratio
n_guide_chapter09186a00800ca763.html#wp1000898
TIA
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