how do I change default gateway? manually and automatically

stringchopper · n00b Joined: 07 Feb 2009 Posts: 50

How do I change the default gateway, shown from "route"

pianosaurus · l33t Joined: 19 Apr 2004 Posts: 944 Location: Bash$

If you need dhcp on wlan0, then you are correct in that your config_wlan0 is useless the way it is now. I would recommend setting it to "dhcp" like you do with eth0. It shouldn't run dhcp unless it has associated with an AP, so there shouldn't be a long wait at boot time anyway. If I'm wrong, and there is, you can work around it by lowering the timeout:

pianosaurus · l33t Joined: 19 Apr 2004 Posts: 944 Location: Bash$

Also, you can set the default gateway manually with route add default 192.168.1.1 (edit: no you can't; see defenderBGs post below), though I don't know if there is an easy way to do this automatically. You may also have to use route del to remove the old default first, but I don't think so. I don't have the opportunity to test it at the moment.
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defenderBG · l33t Joined: 20 Jun 2006 Posts: 817

The correct command would be:
route add default gw 192.168.1.1
and if you want to set a new gw, you have to delete the older one (if you had any).
The command looks like the one above, but yet you need to replace add with del.
You can find out what the default gw is with /sbin/route -n

Automaticly would be with dhcp (emerge dhcp or dhcpcd) then dhclient or dhcpcd <interface>

pianosaurus · l33t Joined: 19 Apr 2004 Posts: 944 Location: Bash$

defenderBG · l33t Joined: 20 Jun 2006 Posts: 817

ok, I just read the name of the thread, your last post and answered

you got me here, so its 1:1.

pianosaurus · l33t Joined: 19 Apr 2004 Posts: 944 Location: Bash$

stringchopper · n00b Joined: 07 Feb 2009 Posts: 50

is there a way to "dynamically" assign a metric to the default gateway that is provided to both the eth0 and wlan0 interface.... instead of adding routes and deleting them through the route command?

ie, if my laptop wired is in (at home), use that gateway as default (0.0.0.0). If and when the wireless comes up (at home, and both interfaces are active), use the gateway for wlan0 as default for internet traffic, and only use the 172.16.0.1 gateway for the traffic to the home LAN

When on the road, of course, use whatever gateway is assigned at the public Access Point as the default.

I'm pretty sure the metric option in the route command would take care of this, if "metric" here works like it does in routing protocols. But I don't want to mess with the route table every time I go out in public and have a different subnet, IP address and default gateway

EDIT: what I was trying to refer to as "metric" would more appropriately be termed "Administrative distance". The AD, in network routing tables is different depending on which protocol put the route in the table, or whether it is physically connected or statically defined. The lower AD is always chosen as the route to put into the routing table.

so what I was thinking is, "wouldn't it be great if" I could have an AD assigned to each default route... say 3 for wired at home, and 2 for wireless (making it preferred), and then use a default lower setting for any default route when in public (so it beats both my home wired and wireless, and I wouldn't have to manually delete and add routes)
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gimpel · Posted: Mon Feb 16, 2009 5:23 pm Post subject:

I guess that's what networkmanager was made for.
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stringchopper · n00b Joined: 07 Feb 2009 Posts: 50

stringchopper · n00b Joined: 07 Feb 2009 Posts: 50

I've noticed that if I start the laptop without the wired cat5 cable plugged in, then bring up wlan0 (using wpa_supplicant, wpa_cli, dhcpcd), the wireless router is the default gateway listed in output of "route".

If I subsequently plug in the cat5 cable, everything works automagically for the wired network. Most importantly, the default gateway for the wired network is added to the route table with a metric (hop) of 1 instead of 0. This accomplishes what I want to do.

So now my question is, how do I ensure that eth0 stays down until wlan0 is up - or how do I ensure that wlan0 comes up first. I think, but am not sure that this takes me back to having wlan0 being set up at boot (correct). That, or leave them both down at boot, and write a script to bring them up in order.

so I recall doing something like "rc-update add net.eth0 default" when installing gentoo. I never did this for wlan0.

Should I simply do this, below, in this specific order, to bring them both up at boot, with wlan0 coming up first?

pianosaurus · l33t Joined: 19 Apr 2004 Posts: 944 Location: Bash$

You could try, but I don't think it matters what order you add them to rc, since the service order is recalculated anyway. The order in /etc/conf.d/net doesn't matter, unfortunately.
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UberLord · Posted: Wed Mar 21, 2018 2:53 pm Post subject:

https://wiki.gentoo.org/wiki/Network_management_using_DHCPCD
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krinn · Watchman Joined: 02 May 2003 Posts: 7470

Doctor UberLord Jones is looking for the lost ark?

Dominique_71 · Posted: Tue Mar 12, 2019 11:35 pm Post subject: