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Juniper SRX Config on PlusNet FTTC BT Infinity

The following JunOS configuration has been tested on PlusNet Fibre broadband running with external BT Openreach Modem. This setup should work with other VDSL/FTTC providers since they use the same underlaying BT infrastructure.

  • The configuration has been tested on SRX210H running JunOS 11.4R9.4 & 12.1X44-D35.5
  • BT Openreach modem connect to interfaces fe-0/0/7 on the SRX

Set the underlaying interface encapsulation to be PPP-Over-Ethernet.

Set PPP Options with Authentication method CHAP.

If your ISP happen to use PAP Authentication method, then you need to reflect that.


Set the pp0 interface MTU.

Your ISP might use a different MTU, so do check it before applying the command.

Set the IP Address on the pp0 interface.

If you happen to get dynamic IP address, you need to use the below negotiate-address option instead of the above static IP(s).

Set the security zone pp0.0 interface WAN (untrust)

If you are experiencing any fragmentation issue, you may want to adjust the tcp-mss setting as below.

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