Hi guys,
We have built all our ISP infrastructure based on the NBN style doubled
tagging of services - in other words each subscriber circuit comes
through on it's own ctag. This makes separating everything really easy
because we pipe each vlan through to different BNG's. However we are now
presented with a wholesaler who does not separate each circuit, but
instead just bridges them all together into a single circuit. We can
distinguish each circuit only by inspecting the DHCP Option82 so that we
can allocate the right IP address, which is fine, but it is hard to
allocate them to use a particular BNG to send and receive traffic.
By the way I am not talking dynamic load balancing just having multiple
BNG with a subsection of the customers on each one - load sharing?
Until now with double tagging, we can reuse the same gateway IP address
(i.e. the side facing the customer) on all the BNG and because each BNG
only sees it's circuits, it will only respond to arps that it should do
on the vlans assigned to it. However with all the customers on the same
circuit it is impossible for multiple BNG to have the same IP address
without creating all sorts of duplicate arps etc. We could turn off arp
on all but one of the BNG and then put up with the asymmetric routing
(makes reverse path filtering impossible) - i.e. send all upload traffic
through a single BNG, but download comes from different ones (according
to what BNG they are allocated to).
I have come up with another hack by using essentially using arp spoofing
where we get a separate box to respond to the arp requests based on what
the source IP is, but I can't help wondering how others have handled
this. The wholesaler tells me there are other ISPs with 5000+ services
on the single circuit (feels like a recipe for a broadcast storm to me).
Oh and no we don't want to use PPPoE :-)
Ideas anyone?
Damian
--
Launtel - We're at your call
Tel: 1800LAUNTEL (1800528683)
Mob: 0418217582
Fax: 1300784109
http://www.launtel.net.au
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