This explains how to configure PPPoE under LACP interface in SRX.

In SRX, you may need to configure the PPPoE under one LACP interface. In this situation, set VLAN tagging under the LACP interface, which will be used by interface pp0. Otherwise, the LACP negotiation will fail.

With VLAN tagging setting

LACPDU

00:20:03.156437 Out 
        Juniper PCAP Flags [Ext], PCAP Extension(s) total length 22
          Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
          Logical Interface Encapsulation Extension TLV #6, length 1, value: Ethernet (14)
          Device Interface Index Extension TLV #1, length 2, value: 34560
          Logical Interface Index Extension TLV #4, length 4, value: 73
          Logical Unit Number Extension TLV #5, length 4, value: 32767
        -----original packet-----
        30:b6:4f:2d:7b:45 > 01:80:c2:00:00:02, ethertype Slow Protocols (0x8809), length 124: LACPv1, length 110
        Actor Information TLV (0x01), length 20
          System 00:10:db:ff:10:00, System Priority 127, Key 129, Port 1, Port Priority 127
          State Flags [Activity, Aggregation, Synchronization, Collecting, Distributing]
          0x0000: 0010 dbff 1000 0081 007f 0001 3d00 0000 
          0x000f: 0214 
        Partner Information TLV (0x02), length 20
          System 3c:94:d5:4f:72:80, System Priority 127, Key 2, Port 1, Port Priority 127
          State Flags [Activity, Aggregation, Synchronization, Collecting, Distributing]
          0x0000: 3c94 d54f 7280 0002 007f 0001 3d00 0000 
          0x000f: 0310 
        Collector Information TLV (0x03), length 16
          Max Delay 0
          0x0000: 0000 0000 0000 0000 0000 0000 0000 
        Terminator TLV (0x00), length 0 (=52)
          0x0000: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x000f: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x001f: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x002f: 
          packet exceeded snapshot
          

Without VLAN tagging setting

LACPDU

00:22:46.938655 Out 
        Juniper PCAP Flags [Ext], PCAP Extension(s) total length 16
          Device Media Type Extension TLV #3, length 1, value: Ethernet (1)
          Logical Interface Encapsulation Extension TLV #6, length 1, value: PPPoE over Ethernet (62) <-- The LACP peer device (SW) will not recognize it, then negotiation will fail.
          Device Interface Index Extension TLV #1, length 2, value: 34560
          Logical Interface Index Extension TLV #4, length 4, value: 74
        -----original packet-----
        30:b6:4f:2d:7b:45 > 01:80:c2:00:00:02, ethertype Slow Protocols (0x8809), length 124: LACPv1, length 110
        Actor Information TLV (0x01), length 20
          System 00:10:db:ff:10:00, System Priority 127, Key 129, Port 1, Port Priority 127
          State Flags [Activity, Aggregation, Default, Expired]
          0x0000: 0010 dbff 1000 0081 007f 0001 c500 0000 
          0x000f: 0214 
        Partner Information TLV (0x02), length 20
          System 00:00:00:00:00:00, System Priority 1, Key 129, Port 1, Port Priority 1
          State Flags [Timeout, Aggregation, Default]
          0x0000: 0000 0000 0000 0081 0001 0001 4600 0000 
          0x000f: 0310 
        Collector Information TLV (0x03), length 16
          Max Delay 0
          0x0000: 0000 0000 0000 0000 0000 0000 0000 
        Terminator TLV (0x00), length 0 (=52)
          0x0000: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x000f: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x001f: 0000 0000 0000 0000 0000 0000 0000 0000 
          0x002f: 
          packet exceeded snapshot

For SRX, in the most instances, the LACP will be used in HA environment, so the following example is an SRX HA scenario.

Configuration:

set interfaces ge-0/0/4 gigether-options redundant-parent reth0
set interfaces ge-0/0/5 gigether-options redundant-parent reth0

set interfaces reth0 vlan-tagging
set interfaces reth0 redundant-ether-options redundancy-group 1
set interfaces reth0 redundant-ether-options lacp active
set interfaces reth0 redundant-ether-options lacp periodic slow
set interfaces reth0 unit 100 encapsulation ppp-over-ether
set interfaces reth0 unit 100 vlan-id 100

set interfaces pp0 unit 0 ppp-options chap default-chap-secret juniper
set interfaces pp0 unit 0 ppp-options chap local-name client1
set interfaces pp0 unit 0 ppp-options chap passive
set interfaces pp0 unit 0 pppoe-options underlying-interface reth0.100
set interfaces pp0 unit 0 pppoe-options auto-reconnect 5
set interfaces pp0 unit 0 pppoe-options client
set interfaces pp0 unit 0 family inet mtu 1454
set interfaces pp0 unit 0 family inet negotiate-address

Verification:

{primary:node0}[edit]
root@SRX# run show lacp interfaces 
Aggregated interface: reth0
    LACP state:       Role   Exp   Def  Dist  Col  Syn  Aggr  Timeout  Activity
      ge-0/0/4       Actor    No    No   Yes  Yes  Yes   Yes     Slow    Active
      ge-0/0/4     Partner    No    No   Yes  Yes  Yes   Yes     Slow    Active
      ge-0/0/5       Actor    No    No   Yes  Yes  Yes   Yes     Slow    Active
      ge-0/0/5     Partner    No    No   Yes  Yes  Yes   Yes     Slow    Active
    LACP protocol:        Receive State  Transmit State          Mux State 
      ge-0/0/4                  Current   Slow periodic Collecting distributing
      ge-0/0/5                  Current   Slow periodic Collecting distributing

{primary:node0}[edit]
root@SRX# run show interfaces terse | match pp0 
pp0                     up    up
pp0.0                   up    up   inet     192.168.1.2    --> 192.168.1.1