Description: Select only messages sent by a host whose IP address belongs to the specified IPv6 subnet. Note that this filter checks the IP address of the last-hop relay (the host that actually sent the message to AxoSyslog), not the contents of the HOST field of the message. You can use both the regular and the compressed format to specify the IP address, for example, 1080:0:0:0:8:800:200C:417A or 1080::8:800:200C:417A. If you do not specify the address, localhost is used.

Use the netmask (also called prefix) to specify how many of the leftmost bits of the address comprise the netmask (values 1-128 are valid). For example, the following specify a 60-bit prefix: 12AB:0000:0000:CD30:0000:0000:0000:0000/60 or 12AB::CD30:0:0:0:0/60. Note that if you set an IP address and a prefix, AxoSyslog will ignore the bits of the address after the prefix. To filter IPv4 addresses, see netmask().

The netmask6() filter is available in AxoSyslog 3.7 and later.