When a PTX device is rebooted/upgraded, the micro BFD that is running over the AE interface tears down the Bidirectional Forwarding Detection (BFD) session and does not appear in the active sessions on the device. Also, Link Aggregation Control Protocol (LACP) for the child interfaces transitions to a "Detached" MUX state. This behavior can be seen when an aggregated interface IP address is used to establish the micro BFD session.
This article explains that micro BFD establishment on PTX Series devices can happen seamlessly only when a loopback address is used for micro BFD session formation.
The following events are seen:
BFD session tears down after session re-establishment.
LACP transitions to Detached MUX state after link flap.
Micro BFD session and LACP remain in Down state unless configuration changes are made.
Example configuration on PTX1000
set interfaces ae103 mtu 9192 set interfaces ae103 aggregated-ether-options bfd-liveness-detection minimum-interval 100 set interfaces ae103 aggregated-ether-options bfd-liveness-detection multiplier 5 set interfaces ae103 aggregated-ether-options bfd-liveness-detection neighbor 172.17.103.0 set interfaces ae103 aggregated-ether-options bfd-liveness-detection local-address 172.17.103.1 set interfaces ae103 aggregated-ether-options link-speed 100g set interfaces ae103 aggregated-ether-options lacp active set interfaces ae103 aggregated-ether-options lacp periodic fast set interfaces ae103 unit 0 family inet address 172.17.103.1/31 set interfaces et-0/0/0:0 gigether-options 802.3ad ae103 jtac@ptx # run show bfd session Detect Transmit Address State Interface Time Interval Multiplier 172.17.103.0 Up et-0/0/0:0 0.500 0.100 5 jtac@ptx# run show lacp interfaces ae103 Aggregated interface: ae103 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity et-0/0/0:0 Actor No No Yes Yes Yes Yes Fast Active et-0/0/0:0 Partner No No Yes Yes Yes Yes Fast Active LACP protocol: Receive State Transmit State Mux State et-0/0/0:0 Current Fast periodic Collecting distributing
After Router Reboot
jtac@ptx # run show bfd session 0 sessions, 0 clients Cumulative transmit rate 0.0 pps, cumulative receive rate 0.0 pps jtac@ptx# run show lacp interfaces ae103 Aggregated interface: ae103 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity et-0/0/0:0 Actor No No Yes Yes Yes Yes Fast Active et-0/0/0:0 Partner No No Yes Yes Yes Yes Fast Active LACP protocol: Receive State Transmit State Mux State et-0/0/0:0 Port Disabled No periodic Detached
PTX Series devices have a limitation as compared to MX Series devices in this aspect. Although devices running Junos OS versions later than 16.1 have the flexibility to configure micro BFD with AE interface addresses for BFD session establishment, this feature does not hold good for PTX Series devices. Micro BFD establishment on PTX series is seen to happen seamlessly only when a loopback address is used for micro BFD session formation.
To establish a micro BFD session, use a loopback address as shown below:
set interfaces ae103 mtu 9192 set interfaces ae103 aggregated-ether-options bfd-liveness-detection minimum-interval 100 set interfaces ae103 aggregated-ether-options bfd-liveness-detection multiplier 5 set interfaces ae103 aggregated-ether-options link-speed 100g set interfaces ae103 aggregated-ether-options lacp active set interfaces ae103 aggregated-ether-options lacp periodic fast set interfaces ae103 unit 0 family inet address 172.17.103.1/31 set interfaces et-0/0/0:0 gigether-options 802.3ad ae103 set interfaces ae103 aggregated-ether-options bfd-liveness-detection neighbor 1.1.1.1 >>>> Loopback IP address of remote device set interfaces ae103 aggregated-ether-options bfd-liveness-detection local-address 2.2.2.2 >> Loopback IP address of local PTX device device jtac@ptx> show lacp interfaces Aggregated interface: ae103 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity et-0/0/0:0 Actor No No Yes Yes Yes Yes Fast Active et-0/0/0:0 Partner No No Yes Yes Yes Yes Fast Active LACP protocol: Receive State Transmit State Mux State et-0/0/0:0 Current Fast periodic Collecting distributing jtac@ptx> show bfd session Detect Transmit Address State Interface Time Interval Multiplier 1.1.1.1 Up et-0/0/0:0 0.500 0.100 5
jtac@ptx> show lacp interfaces Aggregated interface: ae103 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity et-0/0/0:0 Actor No No Yes Yes Yes Yes Fast Active et-0/0/0:0 Partner No No Yes Yes Yes Yes Fast Active LACP protocol: Receive State Transmit State Mux State et-0/0/0:0 Current Fast periodic Collecting distributing jtac@ptx> show bfd session Detect Transmit Address State Interface Time Interval Multiplier 1.1.1.1 Up et-0/0/0:0 0.500 0.100 5
Note: Please do not forgot to allow UDP port 6784 on the lo0 filter for micro BFD sessions. If this port is not allowed micro BFD session will not be established.