Re: [Dnsmasq-discuss] DNS set using dhcp-host expires?
Hey - that worked! Setting my leases to 12 hrs fixed everything. Heh, I guess there are some subtleties in interpreting "infinite". For completeness: # Old. not working. # dhcp-host=,192.168.0.150,livingr oom.internal,infinite # New, working. # Diff: # - 12 hour lease, not infinite # - Don't even need the .internal suffix # Removed hosts file dhcp-host=,192.168.0.150,[::0:1000],livingr oom,12h On Tue, Apr 21, 2020 at 1:54 PM Geert Stappers wrote: > On Tue, Apr 21, 2020 at 09:57:34AM -0400, Jiawen Chen wrote: > > On Tue, Apr 21, 2020 at 3:06 AM Geert Stappers wrote: > > > On Mon, Apr 20, 2020 at 10:27:11PM -0400, Jiawen Chen wrote: > > > > > > > > I'm using dnsmasq for DHCP + DNS on my home LAN and use dhcp-host to > > > > statically assign an IP address and hostname. However, I'm > discovering that > > > > while it works most of the time, sometimes, ssh for example, can't > find the > > > > host by name, only IP. One instance is a Linux VM. Initially I can > ssh into > > > > the VM. But if I power down the VM for say a few days, and start it > back > > > > up, the name is missing (even though it is somehow assigned the same > IP (it > > > > keeps its MAC)). > > > > > > > > dnsmasq.conf: > > > > ``` > > > > # other irrelevant stuff > > > > ... > > > > # Assign 192.168.0.150 to my living room pc > > > > > dhcp-host=,192.168.0.150,livingroom.internal,infinite > > > > > > > > # Assign 192.168.0.151 to my file server > > > > > dhcp-host=,192.168.0.151,fileserver.internal,infinite > > > > ``` > > > > > > I suggest to change the ',infinite' into something like ',12h' > for > > > the servers that are be powered-off of for several days. > > > > > > What I think is that the DNS cache entry expires > > > ( and I think that it is valid behaviour.) > > > > > > > > > Expriment that can be done: > > > > > > * Restart dnsmasq, so it forgets about dhcp-hosts in DNS cache > > > * Check cache dump with SIGUSR1 > > > * Power-on an infinite DHCP client e.g. the Linux VM > > > * Check cache dump with SIGUSR1 > > > * Regular work with the example Linux VM > > > * Power-off the infinite DHCP client > > > * Sample several days the cache dump > > > * Report when the DNS entry of the powered-off server is gone > > > > > > > Thanks! That makes sense. I will give that a shot. > > > Cool. I look forward on feedback. > > > > Groeten > Geert Stappers > -- > Silence is hard to parse > > ___ > Dnsmasq-discuss mailing list > Dnsmasq-discuss@lists.thekelleys.org.uk > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss > ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] DNS set using dhcp-host expires?
On Tue, Apr 21, 2020 at 09:57:34AM -0400, Jiawen Chen wrote: > On Tue, Apr 21, 2020 at 3:06 AM Geert Stappers wrote: > > On Mon, Apr 20, 2020 at 10:27:11PM -0400, Jiawen Chen wrote: > > > > > > I'm using dnsmasq for DHCP + DNS on my home LAN and use dhcp-host to > > > statically assign an IP address and hostname. However, I'm discovering > > > that > > > while it works most of the time, sometimes, ssh for example, can't find > > > the > > > host by name, only IP. One instance is a Linux VM. Initially I can ssh > > > into > > > the VM. But if I power down the VM for say a few days, and start it back > > > up, the name is missing (even though it is somehow assigned the same IP > > > (it > > > keeps its MAC)). > > > > > > dnsmasq.conf: > > > ``` > > > # other irrelevant stuff > > > ... > > > # Assign 192.168.0.150 to my living room pc > > > dhcp-host=,192.168.0.150,livingroom.internal,infinite > > > > > > # Assign 192.168.0.151 to my file server > > > dhcp-host=,192.168.0.151,fileserver.internal,infinite > > > ``` > > > > I suggest to change the ',infinite' into something like ',12h' for > > the servers that are be powered-off of for several days. > > > > What I think is that the DNS cache entry expires > > ( and I think that it is valid behaviour.) > > > > > > Expriment that can be done: > > > > * Restart dnsmasq, so it forgets about dhcp-hosts in DNS cache > > * Check cache dump with SIGUSR1 > > * Power-on an infinite DHCP client e.g. the Linux VM > > * Check cache dump with SIGUSR1 > > * Regular work with the example Linux VM > > * Power-off the infinite DHCP client > > * Sample several days the cache dump > > * Report when the DNS entry of the powered-off server is gone > > > > Thanks! That makes sense. I will give that a shot. Cool. I look forward on feedback. Groeten Geert Stappers -- Silence is hard to parse ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] DNS set using dhcp-host expires?
Thanks! That makes sense. I will give that a shot. On Tue, Apr 21, 2020 at 3:06 AM Geert Stappers wrote: > On Mon, Apr 20, 2020 at 10:27:11PM -0400, Jiawen Chen wrote: > > Hi, > > > ... > > > > I'm using dnsmasq for DHCP + DNS on my home LAN and use dhcp-host to > > statically assign an IP address and hostname. However, I'm discovering > that > > while it works most of the time, sometimes, ssh for example, can't find > the > > host by name, only IP. One instance is a Linux VM. Initially I can ssh > into > > the VM. But if I power down the VM for say a few days, and start it back > > up, the name is missing (even though it is somehow assigned the same IP > (it > > keeps its MAC)). > > > > dnsmasq.conf: > > ``` > > # other irrelevant stuff > > > > no-resolv > > server=8.8.8.8 > > server=8.8.4.4 > > server=1.1.1.1 > > > > expand-hosts > > domain-needed > > bogus-priv > > local=/internal/ > > > > # Assign 192.168.0.150 to my living room pc > > > dhcp-host=,192.168.0.150,livingroom.internal,infinite > > > > # Assign 192.168.0.151 to my file server > > > dhcp-host=,192.168.0.151,fileserver.internal,infinite > > ``` > > I suggest to change the ',infinite' into something like ',12h' for > the servers that are be powered-off of for several days. > > What I think is that the DNS cache entry expires ( and I think that it > is valid behaviour.) > > Expriment that can be done: > > * Restart dnsmasq, so it forgets about dhcp-hosts in DNS cache > * Check cache dump with SIGUSR1 > * Power-on an infinite DHCP client e.g. the Linux VM > * Check cache dump with SIGUSR1 > * Regular work with the example Linux VM > * Power-off the infinite DHCP client > * Sample several days the cache dump > * Report when the DNS entry of the powered-off server is gone > > > Recipe to sabotage the expriment: > while true > do > nslookup linuxVM > output > process_output > if hostname_not_found > then > exit > fi > sleep 2 hour > done > > because it keeps the DNS entry in cache. > > > > > > For these static DHCP leases, is the best practice to set them in > > /etc/hosts instead? > > > > I also discovered --host-record, which does something very similar. Is > > there an advantage in using one option vs the other? > > > > > Groeten > Geert Stappers > -- > Silence is hard to parse > > ___ > Dnsmasq-discuss mailing list > Dnsmasq-discuss@lists.thekelleys.org.uk > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss > ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] DNS set using dhcp-host expires?
On Mon, Apr 20, 2020 at 10:27:11PM -0400, Jiawen Chen wrote: > Hi, > ... > > I'm using dnsmasq for DHCP + DNS on my home LAN and use dhcp-host to > statically assign an IP address and hostname. However, I'm discovering that > while it works most of the time, sometimes, ssh for example, can't find the > host by name, only IP. One instance is a Linux VM. Initially I can ssh into > the VM. But if I power down the VM for say a few days, and start it back > up, the name is missing (even though it is somehow assigned the same IP (it > keeps its MAC)). > > dnsmasq.conf: > ``` > # other irrelevant stuff > > no-resolv > server=8.8.8.8 > server=8.8.4.4 > server=1.1.1.1 > > expand-hosts > domain-needed > bogus-priv > local=/internal/ > > # Assign 192.168.0.150 to my living room pc > dhcp-host=,192.168.0.150,livingroom.internal,infinite > > # Assign 192.168.0.151 to my file server > dhcp-host=,192.168.0.151,fileserver.internal,infinite > ``` I suggest to change the ',infinite' into something like ',12h' for the servers that are be powered-off of for several days. What I think is that the DNS cache entry expires ( and I think that it is valid behaviour.) Expriment that can be done: * Restart dnsmasq, so it forgets about dhcp-hosts in DNS cache * Check cache dump with SIGUSR1 * Power-on an infinite DHCP client e.g. the Linux VM * Check cache dump with SIGUSR1 * Regular work with the example Linux VM * Power-off the infinite DHCP client * Sample several days the cache dump * Report when the DNS entry of the powered-off server is gone Recipe to sabotage the expriment: while true do nslookup linuxVM > output process_output if hostname_not_found then exit fi sleep 2 hour done because it keeps the DNS entry in cache. > > For these static DHCP leases, is the best practice to set them in > /etc/hosts instead? > > I also discovered --host-record, which does something very similar. Is > there an advantage in using one option vs the other? > Groeten Geert Stappers -- Silence is hard to parse ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
