BNG Failover is a complex subject with a multitude of possibilities. Biggest problem is it's mathematically impossible to confirm a device is dead on a network. It could be a routing problem, a physical network problem unrelated to the device. A network split could easily leave most things working on both BNGs, but some probe point might see one or both of the BNGs as dead. Note, nothing you do will help DHCP fail quickly without some intervention. DHCP clients almost never, actually I've not seen it so never, listen to DHCP-FORCE-RENEW. Your outage is thus defined by between 1/2 and 1 x lease period (or how long it takes for end-users to force the issue). PPP is less of an issue it fails after a short time of non-response. Simple case they are the same vendor and the vendor does failover for you. Really if they handle state sharing and it isn't too expensive on performance / cost that is your easiest answer. Split brain issues still exist but they can do the things to mitigate any issues. Other than that, why not move allocation to RADIUS/DHCP and make it static ( or semi-static ), because that gets rid of complexity trading it for less flexibility and the already high routing table cost. Scaling isn't an issue here you only have a few IP's spare to grow into. A.Winfield - Senior Solutions Architect. From: David Lake via Freeradius-Users <freeradius-users@lists.freeradius.org> Date: Friday, 6 November 2026 at 14:19 To: Alexander Clouter via Freeradius-Users <freeradius-users@lists.freeradius.org> Cc: David Lake <d.lake@surrey.ac.uk> Subject: [EXTERNAL] Fast BNG failover and FreeRadius Hello I have 16,000 CPEs (PPPoE) connected across two BNGs - 8,000 homed on each. The issue I have is that we only have 16,000 IP addresses, 8,000 on each BNG and one IP pool. I advertise /32 routes. I know this is not ideal but needs must. I have a total of 59 "spare" addresses and everything is in the same prefix. My question is: If I loose a BNG and the CPEs rehome to the other BNG, how can I be sure that the previous sessions are immediately cleared and the addresses previously on the first BNG become available on the second? Thanks David Sent from Outlook for iOS<https://urldefense.com/v3/__https://aka.ms/o0ukef__;!!IlCVUJ0!vtDp5sKw8QXbc8... > - List info/subscribe/unsubscribe? See https://urldefense.com/v3/__http://www.freeradius.org/list/users.html__;!!Il... -------------------------------------------------------------------- This email is from an external source. Please do not open attachments or click links from an unknown or suspicious origin. Phishing attempts can be reported by using the report message button in Outlook or sending them as an attachment to phishing@sky.uk. Thank you -------------------------------------------------------------------- Information in this email including any attachments may be privileged, confidential and is intended exclusively for the addressee. The views expressed may not be official policy, but the personal views of the originator. If you have received it in error, please notify the sender by return e-mail and delete it from your system. You should not reproduce, distribute, store, retransmit, use or disclose its contents to anyone. Please note we reserve the right to monitor all e-mail communication through our internal and external networks. SKY and the SKY marks are trademarks of Sky Limited and Sky International AG and are used under licence. Sky UK Limited (Registration No. 2906991), Sky-In-Home Service Limited (Registration No. 2067075), Sky Subscribers Services Limited (Registration No. 2340150) and Sky CP Limited (Registration No. 9513259) are direct or indirect subsidiaries of Sky Limited (Registration No. 2247735). All of the companies mentioned in this paragraph are incorporated in England and Wales and share the same registered office at Grant Way, Isleworth, Middlesex TW7 5QD