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what-is-bgp-rib-failure.html
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what-is-bgp-rib-failure.html
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---
url: /2007/12/what-is-bgp-rib-failure.html
title: "What is a BGP RIB failure"
date: "2007-12-19T07:04:00.000+01:00"
tags: [ BGP ]
---
<p>Sometimes you'll see a weird route status (<em>RIB-failure</em>) in your BGP table, for example:</p>
<pre class="code">GW#<strong>show ip bgp ¦ include r></strong><br/><span class="high">r></span> 10.2.0.0/16 10.0.1.2 0 0 65001 i<br/></pre><p>A more thorough investigation of the BGP entry does not give you a lot of additional information:</p>
<pre class="code">GW#<strong>show ip bgp 10.2.0.0</strong><br/>BGP routing table entry for 10.2.0.0/16, version 7<br/>Paths: (1 available, best #1, table Default-IP-Routing-Table, <span class="high">RIB-failure(17)</span>)<br/>Flag: 0x820<br/> Advertised to update-groups:<br/> 1 2<br/> 65001<br/> 10.0.1.2 from 10.0.1.2 (10.0.1.2)<br/> Origin IGP, metric 0, localpref 100, valid, external, best</pre><p>The “mistery” is solved when you inspect the entry in the IP routing table:</p>
<pre class="code">GW#<strong>show ip route 10.2.0.0</strong><br/>Routing entry for 10.2.0.0/16<br/> Known via "static", distance 1, metric 0 (connected)<br/> Routing Descriptor Blocks:<br/> * directly connected, via Null0<br/> Route metric is 0, traffic share count is 1</pre><p>The GW router has a static route that collides with the EBGP route and thus the BGP route cannot be inserted in the IP routing table (as the static route has administrative distance 1).</p>
<p>Let's conclude with a few interesting facts about the RIB failures:</p>
<ul><li>The <a href="http://www.cisco.com/warp/public/459/bgpfaq_5816.shtml#twenty-three">RIB failure</a> feature was introduced in IOS release 12.2T; prior to that, the BGP routes with higher administrative distance than other route sources were silently ignored (similar to all other routing protocols).</li>
<li>You can display BGP routes that are not inserted in the IP routing table with the <strong>show ip bgp rib-failure</strong> command, which also explains why the BGP route was not inserted in the IP routing table.</li>
<li>The BGP routes that are not used due to higher administrative distance are still advertised to all BGP peers (contrary to what most other distance-vector routing protocols do), unless you configure <a href="http://www.cisco.com/univercd/cc/td/doc/product/software/ios122s/122snwft/release/122s25/fs_sbair.htm">bgp suppress-inactive</a> (introducted in 12.2T and 12.0(26)S).</li>
</ul>