Solution to LinuxNATip_conntrack: tablefull

Solution: LinuxNATip_conntrack: tablefull-Linux Enterprise Application-Linux server application information. The following is a detailed description. This Linux NAT is well used. I did not expect that the Internet could not be accessed a few days ago, and the system record also showed the following message:
Ip_conntrack: table full, dropping packet.

Later, I learned that the ip_conntrack module of Linux NAT records the established connection record of the tcp communication protocol, and the preset timeout time is up to five days (432,000 seconds ), so as long as someone in the LAN uses P2P software (such as eDonkey, BT ...) this problem may easily occur.

Solution (1): Increase the value of ip_conntrack_max.

Find the original ip_conntrack_max value:
Command: cat/proc/sys/net/ipv4/ip_conntrack_max

Write the ideal value (each ip_conntrack buffer occupies 292 Bytes)
Command: echo "value">/proc/sys/net/ipv4/ip_conntrack_max
Example: echo "81920">/proc/sys/net/ipv4/ip_conntrack_max
This effect is temporary. If you want to use a new value for each boot, you need to write the above command into/etc/rc. d/rc. local.
Or add: net. ipv4.ip _ conntrack_max = value to/etc/sysctl. conf.
Or run the following command: sysctl-w net. ipv4.ip _ conntrack_max = value.

Solution (2): reduce ip_conntrack timeout time

Reset ip_conntrack_tcp_timeout_established (original value: 432000, unit: seconds)
Command: echo "value">/proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established
Example: echo "600">/proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_timeout_established

The method for automatic configuration upon startup is the same as that for method (1 ).

Other related commands:

View Current ip_conntrack buffer usage
Command: grep conn/proc/slabinfo

Result example: ip_conntrack 3024 4090 384 409 409 1 (the values are described as follows)

Ip_conntrack the cache name
3024 the number of currently active objects
4090 the total number of available objects
384 the size of each object in bytes
409 the number of pages with at least one active object
409 the total number of allocated pages
1 the number of pages per slab are given

Man slabinfo.

Find the top five IP addresses that currently have the most ip_conntrack records
Command: cat/proc/net/ip_conntrack | cut-d ''-f 10 | cut-d' = '-f 2 | sort | uniq-c | sort-nr | head-n 5