From 7d6b68c5d7016aca5372f12e9f0c25f0a108644d Mon Sep 17 00:00:00 2001 From: Simon Kelley Date: Mon, 6 Mar 2023 13:06:03 +0000 Subject: [PATCH] Document suppressing deafult options in --dhcp-option. --- man/dnsmasq.8 | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/man/dnsmasq.8 b/man/dnsmasq.8 index 3d1d96a..41e2e04 100644 --- a/man/dnsmasq.8 +++ b/man/dnsmasq.8 @@ -1297,7 +1297,15 @@ and to set the time-server address to 192.168.0.4, do or .B --dhcp-option = option:ntp-server, 192.168.0.4 The special address 0.0.0.0 is taken to mean "the address of the -machine running dnsmasq". +machine running dnsmasq". + +An option without data is valid, and includes just the option without data. +(There is only one option with a zero length data field currently defined for DHCPv4, 80:rapid commit, so this feature is not very useful in practice). Options for which dnsmasq normally +provides default values can be ommitted by defining the option with no data. These are +netmask, broadcast, router, DNS server, domainname and hostname. Thus, for DHCPv4 +.B --dhcp-option = option:router +will result in no router option being sent, rather than the default of the host on which dnsmasq is running. For DHCPv6, the same is true of the options DNS server and refresh time. + Data types allowed are comma separated dotted-quad IPv4 addresses, []-wrapped IPv6 addresses, a decimal number, colon-separated hex digits