{"id":31,"date":"2009-03-16T11:20:42","date_gmt":"2009-03-16T18:20:42","guid":{"rendered":"http:\/\/www.planetcy.com\/?p=31"},"modified":"2009-03-16T11:20:42","modified_gmt":"2009-03-16T18:20:42","slug":"neighbour-table-overflow","status":"publish","type":"post","link":"http:\/\/www.planetcy.com\/?p=31","title":{"rendered":"Neighbour table overflow"},"content":{"rendered":"\n\n\n
We had an OES 1 box that was unable to communicate on the network, it was acting like it was recieving a DOS attack but traffic analysis did not indicate this. What we found was a situation where the server was on a network with\u00c2\u00a0considerable more hosts then the default ARP cache was able to maintain. The default threshold levels were set too low. We doubled the threshold limits using the information below.<\/p>\n

\u00c2\u00a0<\/p>\n

How to resolve “Neighbour table overflow” problem?<\/td>\n

<\/a><\/td>\n\u00c2\u00a0<\/span><\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u00c2\u00a0<\/p>\n\n\n\n
Gnu\/Linux servers (when used extensively as a server) throw the following messages in log file<\/p>\n

\u00c2\u00a0\u00c2\u00a0kernel: Neighbour table overflow.
\n\u00c2\u00a0 kernel: printk: 100 messages suppressed.
\n\u00c2\u00a0 kernel: Neighbour table overflow.
\n\u00c2\u00a0 kernel: printk: 151 messages suppressed.
\n\u00c2\u00a0 kernel: Neighbour table overflow.<\/em><\/strong><\/p>\n

The solution to the problem is to increase the threshold level for the network devices<\/p>\n

To check the present threshold level 1<\/p>\n

cat \/proc\/sys\/net\/ipv4\/neigh\/default\/gc_thresh1<\/strong>
\n<\/strong><\/p>\n

It will give some value as 128 or 256 or 512.<\/p>\n

This can be increased to the next level.Like if the value is 128 then<\/p>\n

make the thresh1 value as 256 and thresh2 as 512 and thresh3 as 1024.<\/p>\n

echo 256 > \/proc\/sys\/net\/ipv4\/neigh\/default\/gc_thresh1<\/strong><\/p>\n

echo\u00c2\u00a0512 > \/proc\/sys\/net\/ipv4\/neigh\/default\/gc_thresh2<\/strong><\/p>\n

echo\u00c2\u00a01024 > \/proc\/sys\/net\/ipv4\/neigh\/default\/gc_thresh3<\/strong><\/p>\n

<\/strong>This will stop the Error messages that were recieved in the log file<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

This was reposted from gnulinuxclub.org
\nhttp:\/\/www.gnulinuxclub.org\/index.php?option=com_content&task=view&id=333&Itemid=49<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

We had an OES 1 box that was unable to communicate on the network, it was acting like it was recieving a DOS attack but traffic analysis did not indicate this. What we found was a situation where the server was on a network with\u00c2\u00a0considerable more hosts then the default ARP cache was able to […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[18],"tags":[],"class_list":["bg-stuff"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/posts\/31","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=31"}],"version-history":[{"count":1,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/posts\/31\/revisions"}],"predecessor-version":[{"id":32,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=\/wp\/v2\/posts\/31\/revisions\/32"}],"wp:attachment":[{"href":"http:\/\/www.planetcy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=31"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=31"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.planetcy.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=31"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}