This article describes changes caused by the fast-failover knob in the behavior of the Link Aggregation Control Protocol (LACP) in link-protect in Junos 12.2 and above.
When the active leg (collecting and distributing) is deactivated/disabled, the aggregated ether (AE) interface will flap even if there is a second leg in an “attached” state that takes over. Because the AE interface goes down, all Point-to-Point Protocol over Ethernet (PPPoE) clients built on that AE drop, causing an outage.
{master:member0-re0}[edit] lab@RE0-brevaz-H1# run show configuration interfaces xe-2/0/0 gigether-options { 802.3ad ae0; } {master:member0-re0}[edit] lab@RE0-brevaz-H1# run show configuration interfaces xe-14/0/0 gigether-options { 802.3ad ae0; }lab@RE0-brevaz-H1# run show configuration interfaces ae0 flexible-vlan-tagging; aggregated-ether-options { lacp { passive; } } lab@RE0-brevaz-H1# run show lacp interfaces ae0 Aggregated interface: ae0 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity xe-2/0/0 Actor No No Yes Yes Yes Yes Fast Passive xe-2/0/0 Partner No No Yes Yes Yes Yes Fast Active xe-14/0/0 Actor No No No No Yes Yes Fast Passive xe-14/0/0 Partner No No No No No Yes Fast Active LACP protocol: Receive State Transmit State Mux State xe-2/0/0 Current Fast periodic Collecting distributing xe-14/0/0 Current Fast periodic Attached lab@RE0-brevaz-H1# run show interfaces pp0.1073983745 Logical interface pp0.1073983745 (Index 818) (SNMP ifIndex 5608) Flags: Point-To-Point 0x4000 Encapsulation: PPPoE PPPoE: State: SessionUp, Session ID: 1, Session AC name: RE0-brevaz-H1, Remote MAC address: 00:10:95:00:00:01, Underlying interface: demux0.1 (Index 4331) Link: xe-2/0/0.32767 xe-14/0/0.32767 Input packets : 612 Output packets: 613 Keepalive settings: Interval 30 seconds, Up-count 1, Down-count 3 LCP state: Opened NCP state: inet: Opened, inet6: Not-configured, iso: Not-configured, mpls: Not-configured CHAP state: Success PAP state: Closed Protocol inet, MTU: 1492 Flags: Sendbcast-pkt-to-re, uRPF Addresses, Flags: Is-Primary Local: 192.168.1.2
lab@RE0-brevaz-H1# set interfaces xe-2/0/0 disable {master:member0-re0}[edit] lab@RE0-brevaz-H1# commit member0-re0: configuration check succeeds member1-re1: commit complete member1-re0: commit complete member0-re1: commit complete member0-re0: commit complete {master:member0-re0}[edit] lab@RE0-brevaz-H1# run show lacp interfaces ae0 Aggregated interface: ae0 LACP state: Role Exp Def Dist Col Syn Aggr Timeout Activity xe-2/0/0 Actor No Yes No No No Yes Fast Passive xe-2/0/0 Partner No Yes No No No Yes Fast Passive xe-14/0/0 Actor No No Yes Yes Yes Yes Fast Passive xe-14/0/0 Partner No No Yes Yes Yes Yes Fast Active LACP protocol: Receive State Transmit State Mux State xe-2/0/0 Port disabled No periodic Detached xe-14/0/0 Current Fast periodic Collecting distributing lab@RE0-brevaz-H1# run show interfaces ae0 Physical interface: ae0, Enabled, Physical link is Up Interface index: 650, SNMP ifIndex: 1502 Link-level type: Ethernet, MTU: 1522, Speed: 10Gbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 0 Device flags : Present Running Interface flags: SNMP-Traps Internal: 0x4000 Current address: 00:24:dc:47:67:c0, Hardware address: 00:24:dc:47:67:c0 Last flapped : 2014-02-19 15:50:55 EST (00:01:04 ago) *****FLAP Input rate : 992 bps (1 pps) Output rate : 0 bps (0 pps) Logical interface ae0.32767 (Index 817) (SNMP ifIndex 1779) Flags: SNMP-Traps 0x4004000 VLAN-Tag [ 0x0000.0 ] Encapsulation: ENET2 Statistics Packets pps Bytes bps Bundle: Input : 7969 1 934258 992 Output: 501 0 4122 0 Adaptive Statistics: Adaptive Adjusts: 0 Adaptive Scans : 0 Adaptive Updates: 0 Protocol multiservice, MTU: Unlimited Flags: None {master:member0-re0}[edit] lab@RE0-brevaz-H1# run show interfaces pp0.1073983745 error: interface pp0.1073983745 not found {master:member0-re0}[edit] lab@RE0-brevaz-H1#
This situation is caused by a fast-failover knob. If configured, the knob causes the AE member to be considered UP in any LACP state other than DETACHED. This is the default behavior in versions of Junos before 12.2 (such as 11.4X27). In Junos 12.2 and above, the AE member is considered to be DOWN, by default, in any LACP state other than COLLECTING_DISTRIBUTING. Because the active leg that is in collecting-distributing is brought down, the AE interface is brought down until the "attached" leg becomes "collecting-distributing." To provide the same functionality as previous versions of Junos 12.2, the fast-failover knob must be enabled in Junos 12.2 and above. The knob is in effect only when the user is deactivating/disabling the active leg on the DUT, which means that if the peer switch performs the active/disable on the active leg, the port transitions as expected.
Enable the fast-failover knob in Junos 12.2 and above, as follows:
{master:member0-re0}[edit] lab@RE0-brevaz-H1# show interfaces ae0 flexible-vlan-tagging; aggregated-ether-options { lacp { passive; fast-failover; } }