Separating Subscriber Management from Routing: A Software BNG Migration for a Regional ISP
When one platform runs PPPoE termination, CGNAT, BGP, edge routing and subscriber policy, it does not break gracefully as you grow. Every new subscriber session competes with the Internet routing table for the same CPU and the same forwarding capacity, and the only upgrade the platform offers is a bigger box.
A regional ISP came to our Professional Services team at exactly that point. They were running everything on a single integrated router platform that had served them well for years and had simply run out of headroom.
We did not scale the box. We redesigned the subscriber edge.
This was a complex, live migration with no room for customer downtime. We separated subscriber management from routing completely, moved PPPoE and IPoE termination, policy and CGNAT onto a software BNG running on standard x86, and returned the edge routers to doing one thing well: BGP and forwarding. Subscriber scale and routing scale now grow on independent axes, and capacity expands by adding compute rather than replacing a chassis.
The redesign worth highlighting is authentication. The ISP had depended on PPPoE usernames and passwords on customer equipment, a permanent source of support tickets. We removed credentials entirely. PPPoE subscribers are now identified by Circuit-ID from the access network, IPoE subscribers by DHCP Option 82, both keyed to the physical port and resolved against a centralized Splynx AAA platform over RADIUS. Service changes are pushed live through RADIUS CoA, with no subscriber reconnects.
What the ISP gained:
– Subscriber and routing planes that scale independently
– Capacity growth by adding x86, not forklifting hardware
– One identification framework for both PPPoE and IPoE
– Credential-related tickets effectively eliminated
– IPoE delivered as a first-class service the old design could not support
This is the kind of project our Professional Network Services team is built for: complex architecture changes made underneath a production network that cannot stop serving subscribers.
