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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 interfaces fe-0/0/7 unit 0 encapsulation ppp-over-ether

Set PPP Options with Authentication method CHAP.

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

set interfaces pp0 unit 0 ppp-options chap default-chap-secret YOUR-PASSWORD
set interfaces pp0 unit 0 ppp-options chap local-name YOUR-USERNAME
set interfaces pp0 unit 0 ppp-options chap no-rfc2486
set interfaces pp0 unit 0 ppp-options chap passive


Set the PPPoE Options to the underlaying interface along with connection options.

set interfaces pp0 unit 0 pppoe-options underlying-interface fe-0/0/7.0
set interfaces pp0 unit 0 pppoe-options idle-timeout 0
set interfaces pp0 unit 0 pppoe-options auto-reconnect 1
set interfaces pp0 unit 0 pppoe-options client

Set the pp0 interface MTU.

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

set interfaces pp0 unit 0 family inet mtu 1492

Set the IP Address on the pp0 interface.

set interfaces pp0 unit 0 family inet address 80.xxx.xxx.xx/32

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 interfaces pp0 unit 0 family inet negotiate-address

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

set security zones security-zone WAN interfaces pp0.0

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

set security flow tcp-mss all-tcp mss 1300

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