0.0.0.0 as router address in an option-121 is defined in the RFC to mean something different, so substituting it in dnsmasq would be bad. quote RFC 3442
Local Subnet Routes In some cases more than one IP subnet may be configured on a link. In such cases, a host whose IP address is in one IP subnet in the link could communicate directly with a host whose IP address is in a different IP subnet on the same link. In cases where a client is being assigned an IP address on an IP subnet on such a link, for each IP subnet in the link other than the IP subnet on which the client has been assigned the DHCP server MAY be configured to specify a router IP address of 0.0.0.0. For example, consider the case where there are three IP subnets configured on a link: 10.0.0/24, 192.168.0/24, 10.0.21/24. If the client is assigned an IP address of 10.0.21.17, then the server could include a route with a destination of 10.0.0/24 and a router address of 0.0.0.0, and also a route with a destination of 192.168.0/24 and a router address of 0.0.0.0. A DHCP client whose underlying TCP/IP stack does not provide this capability MUST ignore routes in the Classless Static Routes option whose router IP address is 0.0.0.0. Please note that the behavior described here only applies to the Classless Static Routes option, not to the Static Routes option nor the Router option. There's no obvious solution to this one. Cheers, Simon. On 27/04/18 12:34, Olaf Hering wrote: > I had to add DHCP option 121 to server an extra network to the clients in > case one of the clients has to use USB tethering via the mobile phone. > Therefore I added this line, and all is (almost) fine: > > dhcp-option=option:classless-static-route,$other_local_net/24,$interface_IP > > But it is not possible to set $interface_IP to 0.0.0.0 to indicate that > dnsmasq should put in the IPv4 address of the interface from which it serves > the DHCP requests. This is done for a few other DHCP options like > default-router, TFTP server and the like. > > Is this just an oversight, or would there be any downside in handling the > "wildcard" in "classless-static-route"? > > Olaf > > > > _______________________________________________as > Dnsmasq-discuss mailing list > Dnsmasq-discuss@lists.thekelleys.org.uk > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss >
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