[Berlin-wireless] Fwd: ipv6: multiple prefixes+gateways

[André Gaul]

fyi: die diskussion wird gerade auf der DIY-ISP list geführt

  https://lists.ffdn.org/wws/arc/diy-isp/2014-07/thrd1.html#00001

Hat hier vllt schon jemand mit OLSR und source specific routing
herumgespielt? (siehe Beitrag von Christian Franke)

ciao,
André


-------- Original-Nachricht --------
Betreff: ipv6: multiple prefixes+gateways
Datum: Wed, 09 Jul 2014 13:23:17 +0200
Von: André Gaul <gaul at web-yard.de>
An: diy-isp at lists.ffdn.org

Hey!

I've already posted an ipv6-related question in January and received
valuable feedback, especially Saverio pointed me to the excellent
documentation of the ninux architecture [1].

In the meantime the freifunk network got a /32 prefix which can be used
by all freifunk communities. In Berlin, we are in the middle of
distributing a /44 through the (mostly wireless) backbone network (using
OLSR).

At least one problem still puzzles us and occurs if multiple gateways
(for ::/0) are announced via OLSR but different prefixes are assigned to
each gateway.

Example:
 * GW_A is one of our BGP routers and takes care of subnet A
   (e.g., 2001:bf7:750::/44 for Berlin)
 * GW_B is a gateway connected to DSL line and is assigned the subnet B
   by the DSL provider (e.g. 2001:470:815::/48)
 * Now a client sends an IP packet with a source address from subnet A
   and some destination address outside the mesh to its default
   gateway. The default gateway runs OLSR and sees 2 gateways (GW_A and
   GW_B) for ::/0. Maybe GW_B is closer and the packet is therefore
   routed through GW_B.

The problem is that a DSL operator may choose to drop such a packet
since it does not originate from the assigned subnet (subnet B).

So my question is: are there any experiences with source-sensitive
routing with ipv6 in other communities or DIY ISPs?

I haven't found anything in [1] but maybe I've overlooked something. ;)

Thanks,
André

[1] http://nnx.me/ninuxarchitecturev1


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