netdev - Re: Route fallback issue

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Message-ID: <alpine.LFD.2.20.1806202139330.1969@ja.home.ssi.bg>
Date:   Wed, 20 Jun 2018 22:00:30 +0300 (EEST)
From:   Julian Anastasov <ja@....bg>
To:     Akshat Kakkar <akshat.1984@...il.com>
cc:     netdev <netdev@...r.kernel.org>,
        cronolog+lartc <cronolog+lartc@...glemail.com>,
        lartc <lartc@...r.kernel.org>,
        Erik Auerswald <auerswal@...x-ag.uni-kl.de>
Subject: Re: Route fallback issue


	Hello,

On Wed, 20 Jun 2018, Akshat Kakkar wrote:

> Hi netdev community,
> 
> I have 2 interfaces
> eno1 : 192.168.1.10/24
> eno2 : 192.168.2.10/24
> 
> I added routes as
> 172.16.0.0/12 via 192.168.1.254 metric 1
> 172.16.0.0/12 via 192.168.2.254 metric 2
> 
> My intention : All traffic to 172.16.0.0/12 should go thru eno1. If
> 192.168.1.254 is not reachable (no arp entry or link down), then it
> should fall back to eno2.

	You can also try alternative routes. But as the
kernel supports only default alternative routes, you can
put them in their own table:

# Alternative routes use same metric!!!
ip route append default via 192.168.1.254 dev eno1 table 100
ip route append default via 192.168.2.254 dev eno2 table 100
ip rule add prio 100 to 172.16.0.0/12 table 100

	Of course, you will get better results if an user space
tool puts only alive routes in service after doing health
checks of all near gateways.

Regards

--
Julian Anastasov <ja@....bg>