ARP table overflow tuning: Difference between revisions

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{{Portal|User}}
{{Portal|Deployment}}
{{Portal|Network}}
By default, the maximum number of entries that the ARP table can store is set to 1024.
By default, the maximum number of entries that the ARP table can store is set to 1024.
In case of a virtualization configuration with more than 1024 nodes '''on the same ethernet network''', this limitation will be reached.
In case of a virtualization configuration with more than 1024 nodes '''on the same ethernet network''', this limitation will be reached.
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Choose one of the following:
Choose one of the following:
* Using the <code>proc filesystem</code>
* Using the <code>proc filesystem</code>
  cat 4096 > /proc/sys/net/ipv4/neigh/default/gc_thresh3
  echo 4096 > /proc/sys/net/ipv4/neigh/default/gc_thresh3
  cat 2048 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
  echo 2048 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
  cat 1024 > /proc/sys/net/ipv4/neigh/default/gc_thresh1
  echo 1024 > /proc/sys/net/ipv4/neigh/default/gc_thresh1


* Using <code class="command">sysctl</code>
* Using <code class="command">sysctl</code>
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh3 = 4096
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh3=4096
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh2 = 2048
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh2=2048
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh1 = 1024
  /sbin/sysctl -w net.ipv4.neigh.default.gc_thresh1=1024


* Setting it up definitively editing the <code class="file">/etc/sysctl.conf</code> configuration file and adding:
* Setting it up definitively editing the <code class="file">/etc/sysctl.conf</code> configuration file and adding:

Latest revision as of 17:39, 20 April 2009

By default, the maximum number of entries that the ARP table can store is set to 1024. In case of a virtualization configuration with more than 1024 nodes on the same ethernet network, this limitation will be reached.

Linux offers the possibility to overcome this limitation using the sysctl interface.

Choose one of the following:

  • Using the proc filesystem
echo 4096 > /proc/sys/net/ipv4/neigh/default/gc_thresh3
echo 2048 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
echo 1024 > /proc/sys/net/ipv4/neigh/default/gc_thresh1
  • Using sysctl
/sbin/sysctl -w net.ipv4.neigh.default.gc_thresh3=4096
/sbin/sysctl -w net.ipv4.neigh.default.gc_thresh2=2048
/sbin/sysctl -w net.ipv4.neigh.default.gc_thresh1=1024
  • Setting it up definitively editing the /etc/sysctl.conf configuration file and adding:
net.ipv4.neigh.default.gc_thresh3 = 4096
net.ipv4.neigh.default.gc_thresh2 = 2048
net.ipv4.neigh.default.gc_thresh1 = 1024

See man 7 arp for more info on the meaning to the gc_threshX sysctl.