On 07/11/2021 23:47, Juliusz Chroboczek wrote:
I have a hack which pings from each site to see if its own internet
connection is up. If it is, it installs a default route.
How do the pings reach the Internet before a default route has been
installed?
:)
I have an "isp" route table which has that default route, and a rule to
use that table for packets which originate from the external interface
of the internet connection:
$ ip route show table isp
default via 169.255.147.129 dev bond-net
169.255.147.128/29 dev bond-net scope link
$ ip rule show
0: from all lookup local
32765: from 169.255.147.134 lookup isp
32766: from all lookup main
32767: from all lookup default
The hack is then to ping the internet (pick a famously up site :))
setting the source fo the pings to that external interface IP. If
packets return, I deem that link to be good and install a default route
as usual, with a metric that reflects my preference for that link.
The idea was then that Babel would install additional default routes for
the "other" links which are up elsewhere in the mesh, and if their
metric was lower than the metric of this link, they would "win" for this
site.
Babel will not put its own proto route into the table, if there is
a static route already configured.
That's not quite right. Babeld will refuse to install a route that has the
same destination as a route that it redistributes, but will blindly ignore
any routes that it's not redistributing. So the solution is to make sure
that Babeld does not see your default route.
1. Make sure that the static route is not visible to babeld:
redistribute ip 0.0.0.0/0 proto xxx allow
redistribute ip :::/0 proto xxx allow
where xxx is *not* the protocol of the static route. (This is the
difference with your configuration, where you ask Babeld to
redistribute routes for all protocols, including the one of the
static route.)
2. When the route has been shown to be routable, have your reachability
daemon install a route tagged with the protocol that Babeld redistributes:
ip route add ... proto xxx
What's not clear to me then is how to get the local default route to
propagate to other sites in the mesh.
Do I want to install TWO default routes with my script, one to be used
and one to be propagated?
Here's the issue. Each site is constantly checking its own link. If that
link is good, it needs to put a route in with a relevant metric for that
link, *and* propagate that route to other sites. I'm not sure how that
route can be simultaneously redistributed and ignored.
What I would like for most sites is that the daemon-installed route has
a high metric, and the Babel-installed route has a low metric, so that
traffic flows away from that site in the mesh, and out through the
preferred link.
To answer Dave's question about link preference, I have two ISPs but the
deal with one is that it is a backup and traffic should only flow to
them if it doesn't flow to the first one.
Mark
_______________________________________________
Babel-users mailing list
[email protected]
https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
