Op dinsdag 26 oktober 2010 01:54:00 schreef P. Christeas: > On Monday 25 October 2010, you wrote: > > Op maandag 25 oktober 2010 00:56:32 schreef P. Christeas: > > > On Sunday 24 October 2010, Maarten Vanraes wrote: > > > > I would propose the following: > > > > > > > > A.) by default, add for every interface, a little advanced routing > > > > which makes packets return from the same way they came. > > > > This usually is only useful with incoming packets, but can still be > > > > useful if laptops have for example 2 gateways because the wifi is > > > > still on and the cable is too. That would mean that from both > > > > interfaces it'd be possible to use ssh or vnc or whatever. > > > > > > > > B.) if we have multiple gateways (like in that case), have them use > > > > both balancedly. ie: start a small daemon which checks which of the > > > > gateways is up or down; and change the default gateway accordingly, > > > > or even both in some kind of balanced mode. (with advanced routing.) > > > > > > > > This would have the benefit, if you have really clueless users with a > > > > laptop; that everything will still work well. and you're still able > > > > to take over his laptop. > > > > > > Will that do ? : > > > http://git.hellug.gr/?p=xrg/ip-multipath;a=summary > > > > > > (note to myself: I have to build a man^Hgeia rpm..) > > > > This looks like something different than what i intended; isn't this more > > of a configured thing? > > > > I would propose some changes to the networkingscripts. when having > > gateway addresses (through various means) to change the stuff. > > Please excuse me for the lack of documentation. > This script is an addon over the if-up scripts, which adds the support for > multiple gateways to and from the internet. > You only need to place this script in > /etc/sysconfig/network-scripts/ifup.d/ and then some extra variables will > help you configure the interfaces: MULTIPATH_TABLE=10 # needed, just a > unique one per interface > MULTI_GATEWAY_IN=1.2.3.4 # if this is a gateway route, but don't want to > use # the interface by default > MULTI_GATEWAY=1.2.3.4 # default route, along with other interfaces. > > The functionality is provided by kernel itself. By using multiple kernel > routing tables, the first thing you achieve is to have your server listen > on all its internet-routing interfaces, so that you can connect *to* your > server from any of them. This is _extremely_ useful, because it allows you > to ssh to the server from /any/ interface that works, and then fix all the > others. Saves the day. > The second one, a little more tricky, is to have multiple routes to the > internet. With TCP connections, this works /almost/ fine, because it may > assign each connection to a different gateway, thus load-balancing. With > UDP ones, well, this is not really working (AFAIK). However, if you also > give different weights, it may activate the kernel's /slow/ transition > mechanism (5-10 min responses), which will automatically pick the first > working interface as its default gw (even if all interfaces are up and > some of them respond with ICMP unreachable, it will work).
Ah, then i guess we are on the same page after all. the first part neatly conforms to my point A. now the thing is, you can indeed configure that; but perhaps it would be better to let it autoconfigure; depending on the IP address at the time, when the gateways are being added as default routes. thus not needing any extra configuration. i was under the impression that routes are being cached; so that even UDP will not have any problem here. I have not heard about /slow/ transition mechanism though; i don't know what you mean by this.
