Static DHCP mappings aren't available on DNS
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	thinkl33t
	May 25 2018, 10:31 AM

Description

I ran into the issue as mentioned in https://phabricator.vyos.net/T103, and attempted to use the solution as specified:

set service dhcp-server global-parameters "use-host-decl-names on;"

However, i have an issue with this solution - one of my servers print is available on multiple VLANs - main.local, print.local, and guest.local, and giving it a static IP in each causes dhcpd to fail. This is what the prepending of the dhcp shared network name was meant to solve.

I'd like these hostnames to still be available in dns, but keep the prepended shared network name in dhcpd.conf.

I suggest that when a static lease is added, the DHCP configuration script should add the machine's fqdn / ip address into /etc/hosts, and remove it when a static lease is removed.

Details

Difficulty level: Normal (likely a few hours)
Version: VyOS 1.2.0-rolling+201805210337
Why the issue appeared?: Will be filled on close
Is it a breaking change?: Unspecified (possibly destroys the router)
Issue type: Bug (incorrect behavior)

Related Objects
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		Status	Subtype	Assigned	Task
		Open		None	T2464 DNS bugs (parent task)
		Open	BUG	None	T659 Static DHCP mappings aren't available on DNS

Event Timeline

thinkl33t created this task.May 25 2018, 10:31 AM

Inserting FQDN seems reasonable, but we need to think carefully when FQDN should come from, and if we use the "system domain-name" option, what should we do if it's not present.

syncer triaged this task as Normal priority.May 27 2018, 9:36 AM

Moving this out of 1.2.0, at least until we decide what to do when domain is not configured.

I've implemented this in our ansible-derived vyos configuration by allowing the static addresses to be generated with the VLAN prepended and adding a system static-host-mapping for the fqdn to ip.

Nothing vyos-side needs changing to do this, might be worth us documenting it as an option somewhere though?

set service dhcp-server shared-network-name VLAN{{vlan}} subnet {{network.address}} static-mapping {{static_lease.key}} ip-address {{static_lease.value.ip}}
set service dhcp-server shared-network-name VLAN{{vlan}} subnet {{network.address}} static-mapping {{static_lease.key}} mac-address {{static_lease.value.mac}}
set system static-host-mapping host-name {{static_lease.key}}.{{network.tag}}.example.org inet '{{static_lease.value.ip}}'

pasik subscribed.Mar 12 2019, 6:13 PM

jjakob added a parent task: T2464: DNS bugs (parent task).May 15 2020, 9:36 PM

dmbaturin changed Difficulty level from Unknown (require assessment) to Normal (likely a few hours).Jan 27 2021, 7:13 PM

dmbaturin set Is it a breaking change? to Unspecified (possibly destroys the router).

rps mentioned this in T2291: Bad hostnames in /etc/hosts with static-mapping in dhcp server config.Feb 27 2021, 11:43 PM

CuBiC3D subscribed.May 20 2021, 1:01 PM

dmbaturin added a project: test.Jul 29 2021, 1:02 PM

dmbaturin set Issue type to Bug (incorrect behavior).Sep 3 2021, 7:37 AM

syncer edited projects, added VyOS 1.3 Equuleus (1.3.0); removed VyOS 1.3 Equuleus.Nov 6 2021, 11:25 AM

syncer edited projects, added VyOS 1.3 Equuleus (1.3.3); removed VyOS 1.3 Equuleus (1.3.0).Aug 29 2022, 7:06 AM

syncer edited projects, added VyOS 1.3 Equuleus (1.3.4); removed VyOS 1.3 Equuleus (1.3.3).Jul 12 2023, 9:45 PM

syncer edited projects, added VyOS 1.3 Equuleus (1.3.5); removed VyOS 1.3 Equuleus (1.3.4).Aug 25 2023, 9:31 PM