02.10.2013 Views

FTOS Configuration Guide for the C-Series - Force10 Networks

FTOS Configuration Guide for the C-Series - Force10 Networks

FTOS Configuration Guide for the C-Series - Force10 Networks

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Figure 338 illustrates <strong>the</strong> choices parameters BGP goes through to select <strong>the</strong> best path. The list following<br />

<strong>the</strong> illustration details <strong>the</strong> path selection criteria.<br />

Figure 338 BGP Best Path Selection<br />

Largest<br />

Weight<br />

No, or Not Resulting in a Single Route<br />

Highest<br />

Local Pref<br />

Locally<br />

Originated<br />

Path<br />

Best Path selection details<br />

Shortest<br />

AS Path<br />

Lowest<br />

Origin<br />

Code<br />

1. Prefer <strong>the</strong> path with <strong>the</strong> largest WEIGHT attribute.<br />

2. Prefer <strong>the</strong> path with <strong>the</strong> largest LOCAL_PREF attribute.<br />

Lowest<br />

MED<br />

Learned<br />

via EBGP<br />

A Single Route is Selected and Installed in <strong>the</strong> Forwarding Table<br />

Lowest<br />

NEXT-HOP<br />

Cost<br />

• Prefer <strong>the</strong> path that was locally originated via a network command, redistribute command<br />

or aggregate-address command.<br />

• Routes originated via <strong>the</strong> network or redistribute commands are preferred over routes<br />

originated via <strong>the</strong> aggregate-address command.<br />

3. Prefer <strong>the</strong> path with <strong>the</strong> shortest AS_PATH (unless <strong>the</strong> bgp bestpath as-path ignore command is<br />

configured, <strong>the</strong>n AS_PATH is not considered). The following criteria apply:<br />

• An AS_SET has a path length of 1, no matter how many ASs are in <strong>the</strong> set.<br />

Tie Breakers<br />

Short<br />

Cluster<br />

List<br />

from<br />

Lowest<br />

BGP ID<br />

Lowest<br />

Peering<br />

Addr<br />

466 Border Gateway Protocol (BGP)

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!