Re: IPv6 Dynamic gateways in separate routing tables

["Adrian Moreno" <adrian_linux@gmx.com>]

Hi Remy,

> You're implementing policy based routing. You should use iproute2's ip rule " ip -6 rule ... " to enforce source to gateway mapping.
I am. I am using ip -6 rule to enforce route lookup to a separate routing table: 
  
   "ip -6 rule add from $IPv6_1 table $T_1"

but I don't know how to add a default route in table $T_1 that uses the dynamic gateway. If I don't add any default gateway route in $T_1, any address that doesn't match the subnet route ( "ip -6 route add $SUBNET_1 dev $IF_1 table $T_1" ), will be routed to the first default gateway that is listed in "ip -6 route show default". That is obviously not a valid solution because the order of those gateways is not predictable.

Thanks.
Adrian

----- Original Message -----
From: Remy Mudingay
Sent: 10/09/13 03:12 PM
To: Adrian Moreno
Subject: Re: IPv6 Dynamic gateways in separate routing tables
 Hi Adrian,

You're implementing policy based routing. You should use iproute2's ip rule " ip -6 rule ... " to enforce source to gateway mapping. 

Remy

> On Oct 9, 2013, at 15:20, "Adrian Moreno" <adrian_linux@gmx.com> wrote:
> 
> Hi all,
> 
> I have a multihomed system (very similar to the one described in LARTC HowTo Section 4.2. Routing for multiple uplinks/providers) with IPv6 addresses.
> 
> I want to create a routing table per interface to be able to route the traffic depending on the source address using IPv6 addresses and dynamic gateways.
> How do I set the default gateway to be dynamic in a separate routing table?
> 
> My current configuration is:
> IF_1: Interface 1
> SUBNET_1: the subnet connected to Interface 1
> IPv6_1: IPv6 address configured on Interface 1
> T_1: Routing table for Interface 1
> 
> IF_2: Interface 2
> SUBNET_2: the subnet connected to Interface 2 
> IPv6_2: IPv6 address configured on Interface 2
> T_2: Routing table for Interface 2
> 
> Configuration:
> ip -6 route add $SUBNET_1 dev $IF_1 table $T_1
> ip -6 rule add from $IPv6_1 table $T_1
> 
> I am clearly missing one route, that should look like:
> ip -6 route add default via <GATEWAY_1> tab $T_1
> How should I set this route to use the dynamically obtained gateway?
> 
> The dynamic gateways are listed in the "default" routing table as:
> % ip -6 route show default
> default via DYNAMIC_GWv6_1 dev IF_1 proto kernel metric ....
> default via DYNAMIC_GWv6_2 dev IF_2 proto kernel metric ....
> 
> The order in which these routes are listed is arbitrary (restarting /etc/init.d/networking re-shuffles them).
> Is there a way to ensure that a packet being sent from IPv6_1 goes out via the correct gateway (DYNAMIC_GWv6_1) and interface (IF_1)?
> 
> Many thanks in advance for any help.
> 
> Adrian
> 
> 
> 
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