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<article>

<title>
cflowd-2-0 FAQ
</title>
<author>Daniel W. McRobb
<date>May 27, 1999

<abstract>
This document contains answers to Frequently Asked Questions regarding 
<tt>cflowd-2-0</tt>.

</abstract>

<toc>

<sect>Problems Starting <tt>cflowdmux</tt> and <tt>cflowd</tt>
<p>

<sect1>On Solaris 2.x, why does <tt>cflowdmux</tt> report a
 shmget() error at startup (and then fail to work)?
<p>

Solaris' default shared memory segment size maximum is very low
(1MB).  <tt>cflowdmux</tt> wants a shared memory segment for packet
buffers that's just over 1MB, which is beyond the default maximum
limit imposed by the operating system.  To permit a larger shared
memory packet buffer, you should add this to /etc/system:

<verb>
      set shmsys:shminfo_shmmax = 4194304
</verb>

and reboot the host.  The setting above is 4MB; a higher setting
is acceptable as well (no resources are allocated by this change,
since shared memory is allocated on demand).

Note that the packet buffer size may be configured using the
<tt>PKTBUFSIZE</tt> setting in the <tt>OPTIONS</tt> stanza in
<tt>cflowd.conf</tt>.
<p>

<sect>Data Problems
<p>

<sect1>What causes entries in the AS matrix to have the source or
 destination AS set to zero?
<p>

<itemize>
  <item>Flows for traffic destined for the router's local AS will have a
    destination AS of 0.  Flows for traffic coming from the router's
    local AS will have a source AS of 0.
  <item>Flows for traffic destined for the router will have a destination 
    AS of 0 and a destination interface index of 0.
  <item>Flows for unroutable traffic will have a destination AS of 0, a
    nexthop of 0.0.0.0, an output interface index of 0 and a destination
    netmask length of 0.
  <item>Prefix cache misses when not running CEF.  This can cause failed
    AS and netmask lookups on both the source and destination.  Flows for
    this traffic will have a source AS of 0 and a source netmask length of 0
    and/or a destination AS of 0 and destination netmask length of 0.  In
    the case of a source AS of 0 and netmask length of 0, the typical cause
    is asymmetric traffic (the router is only seeing one direction of the
    flow because traffic in the other direction takes a different path which
    circumvents the router or the flow is unidrectional).

    Solution: use CEF.
  <item>Flows for multicast traffic appear to always have both source and
    destination AS set to 0.
</itemize>

</article>
