[lug] Ubuntu 18.04 Route Metric
John Hernandez
jph at jph.net
Fri May 21 11:04:43 MDT 2021
That sounds like a good plan. Oh, and just to toss in one more bad idea -
you could also try to configure your DHCP client not to request a default
route for that interface:
https://blog.dachary.org/2014/05/06/enable-secondary-network-interface-and-ignore-the-default-route/
On Fri, May 21, 2021 at 11:01 AM D. Stimits <stimits at comcast.net> wrote:
>
>
> On 05/21/2021 10:56 AM John Hernandez <jph at jph.net> wrote:
>
>
> It occurs to me that you could also switch from DHCP-client to a static
> configuration for the LAN interface on your Ubuntu server, whilst leaving
> the public interface configured as DHCP-client. If you want to be thorough
> about it, you could also remove your statically assigned IP address from
> the Private LAN DHCP server's address pool.
>
> The DHCP router is just an appliance. I don't have an Ubuntu server. A lot
> of small embedded devices depend on DHCP, but I am probably going to have
> to go with static assignment on the private LAN. I am thinking that since a
> static address won't send a DHCP request, and since the address is reserved
> for that MAC address, then I could just go static and not muck with the
> router. I do really wish though that the router had more options for
> default route.
>
>
> On Fri, May 21, 2021 at 10:51 AM D. Stimits < stimits at comcast.net> wrote:
>
>
>
> On 05/21/2021 10:29 AM John Hernandez < jph at jph.net> wrote:
>
>
> In this case, I agree with Zan that the "right way" to fix this is to make
> the DHCP server on the private network stop providing a default route. If
> that DHCP server doesn't have the proper knobs to accomplish that, I would
> be inclined to turn that DHCP off altogether and deploy a better DHCP
> server on the private LAN.
>
> I wish I could :(
>
> I will look closer at the router and see if there is any way to disable
> that.
>
> On Fri, May 21, 2021 at 10:24 AM D. Stimits < stimits at comcast.net> wrote:
>
>
>
> On 05/20/2021 7:01 PM Bear Giles < bgiles at coyotesong.com> wrote:
>
>
> I don't recall if netplan was supported in 18.04. It's taken a bit of time
> to get the hang of it(*) but the basics aren't too bad - it sounds like you
> want to set static values so it should be pretty straightforward.
>
> I want the metric to be custom at low priority (higher metric), or else to
> not have a default route at all on the private network (this is
> preferable). I just don't know how to do this while keeping DHCP.
>
> The private net router is mine, but it seems useless in setting metric.
> I've changed "priority" in "nm-connection-editor", but this is ignored
> (apparently I can set to use DHCP or many other things from
> nm-connection-editor, but priority is summarily ignored). Can netplan be
> used to allow all DHCP, except to intercept metric or default route on one
> interface to either remove default route or force a low priority metric?
> This might be the right way.
>
>
> Part of one of my files is:
>
> # Let NetworkManager manage all devices on this system
> network:
> version: 2
> renderer: NetworkManager
> ethernets:
> # onboard-NIC
> enp0s31f6:
> dhcp4: false
> addresses:
> - 192.168.1.3/24
> - 10.0.10.3/24
> - 10.0.20.3/24
> - 10.0.90.3/24
> # gateway4: 192.168.1.1
> nameservers:
> search:
> - lan
> addresses:
> - 10.0.20.15
> - 10.0.10.10
> - 8.8.8.8
> routes:
> - to: 0.0.0.0/0
> via: 192.168.1.1
> metric: 100
> # home GW to work VPN
> - to: 172.27.0.0/16
> via: 192.168.1.200
> metric: 10
>
> It has additional stanzas for the 10 Gbps(!) NICs. A system with wifi
> connectivity has
>
> # Let NetworkManager manage all devices on this system
> network:
> version: 2
> renderer: NetworkManager
>
> wifis:
> # all-wlans:
>
> wlp3s0:
> match: {}
> access-points:
> homewifi:
> password: 'password'
> dhcp4: false
> addresses:
> - 192.168.1.9/24
> - 10.0.10.9/24
> gateway4: 192.168.1.1
> nameservers:
> search:
> - lan
> addresses:
> - 10.0.10.15
> - 10.0.10.10
>
>
> FWIW I've tried to match on MAC address - it would be nice because I
> could have one configuration file that I could deploy to all systems
> instead of needing to customize them, but I haven't been able to get them
> to work. Here's one attempt:
>
> wifis:
> wlx9cefd5fcd82b:
> match:
> name: wlx9cefd5fcd82b
> macaddress: "9c:ef:d5:fc:d8:2b"
>
> but I don't recall what had as the name . (That's the system's device
> name based on the MAC address.) Hmm... maybe I should have tried 'all-wans'.
>
> Bear
>
> On Thu, May 20, 2021 at 9:54 AM Zan Lynx < zlynx at acm.org> wrote:
>
> On 5/20/21 8:34 AM, D. Stimits wrote:
> > Does anyone here know how to force my Ubuntu 18.04 to completely
> > leave out a default route for my private router? Or to permanently
> > set that route to a low priority, or to permanently set my public
> > interface to metric of 1?
>
> You must be using DHCP or this would not apply.
>
> Change your DHCP on your private network so that it does not apply any
> default route. Then each DHCP client will only have routes to the
> networks controlled by the private router.
>
> --
> Knowledge is Power -- Power Corrupts
> Study Hard -- Be Evil
>
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