This article describes a  scenario where the subscriber/CPE fails to establish a PPPoE session when running an Enhanced Subscriber Management build starting from Junos 15.1R3 and higher, which is a next-generation broadband edge software architecture for Subscriber Management.

In the following scenario, two CPEs are installed for redundancy purposes. Both CPEs are getting different IP addresses but have the same Framed-Route.  As a result, one CPE is able to connect while the other fails to connect.

The following attributes were sent by radius for both the subscriber.

May 19 18:52:31.527601 radius-access-accept: Framed-Route received: 198.19.23.0/29 198.19.22.5 1 <-- Subscriber A
May 19 18:54:31.626908 radius-access-accept: Framed-Route received: 198.19.23.0/29 198.19.22.6 5 <-- Subscriber B

Configuration

jtac@ERX-MX960-II-RE0# show groups rnayar-AGC dynamic-profiles PPPOE
interfaces {
    pp0 {
        unit "$junos-interface-unit" {
            no-traps;
            ppp-options {
                pap;
            }
            pppoe-options {
                underlying-interface "$junos-underlying-interface";
                server;
            }
            keepalives interval 30;
            family inet {
                unnumbered-address lo0.0;
            }
        }
    }
}
routing-options {
    access {
        route $junos-framed-route-ip-address-prefix {
            next-hop "$junos-framed-route-nexthop";
            metric "$junos-framed-route-cost";
            preference "$junos-framed-route-distance";
            tag "$junos-framed-route-tag";
        }
    }

Subscriber-A

Subscriber is able to connect successfully.

jtac@ERX-MX960-II-RE0# run show subscribers extensive
Type: PPPoE
User Name: rnayar-xtac1
IP Address: 198.19.22.5
IP Netmask: 255.255.255.255
Logical System: default
Routing Instance: default
Interface: pp0.3221225873
Interface type: Dynamic
Underlying Interface: xe-8/0/0.1661
Dynamic Profile Name: PPPOE
Dynamic Profile Version: 1
MAC Address: 00:13:01:00:00:01
State: Active
Radius Accounting ID: 422
Session ID: 422
PFE Flow ID: 483
VLAN Id: 1661
Login Time: 2017-05-19 18:52:31 IST
Dynamic configuration:
  junos-framed-route-ip-address-prefix: 198.19.23.0/29
      junos-framed-route-nexthop: 0.0.0.0
          junos-framed-route-cost: 1
 
 
jtac@ERX-MX960-II-RE0# run show system subscriber-management route prefix 198.19.23.0/29
 
Route:  198.19.23.0/29
     Routing-instance:         default:default
     Kernel rt-table id :      0
     Family:                   AF_INET
     Route Type:               Access
     Protocol Type:            (null)
     Interface:                pp0.3221225873
     Interface index:          483
     Internal Interface index: 483
     Route index:              317
     Next-Hop:                 597
     Reference-count:          1
     L2 Address:               00:13:01:00:00:01
     Flags:                    0x100000
     Dirty Flags:              0x0

Subscriber-B

Subscriber failed to connect as bbe-smgd daemon sends NACK with following the error message:

Upon debugging the error condition, it was noticed that bbe-smgd is rejecting the subscriber due to duplicate Framed-Route.

AAA

BBE-SMGD

Next Generation Subscriber Management handling is functioning as designed when a duplicate prefix is configured. The second identical prefix/prefix_len will fail. In earlier releases, even if the route duplication was allowed for add, only one route would be added to the route table.