[lug] Ubuntu 18.04 Route Metric

D. Stimits stimits at comcast.net
Fri May 21 10:51:39 MDT 2021



>     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 mailto:stimits at comcast.net > wrote:
> 
>         > >          
> > 
> >             > > >             On 05/20/2021 7:01 PM Bear Giles < bgiles at coyotesong.com mailto: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:
> > >                     -http://192.168.1.3/24
> > >                     -http://10.0.10.3/24
> > >                     -http://10.0.20.3/24
> > >                     -http://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:http://0.0.0.0/0
> > >                        via: 192.168.1.1
> > >                        metric: 100
> > >                      # home GW to work VPN
> > >                      - to:http://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:
> > >                           -http://192.168.1.9/24
> > >                           -http://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 mailto: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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> > > > 
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