How loop protect works over VSX
Assume that you have the loop protect feature enabled on lag 1/1/1 on the primary VSX switch and loop protect enabled on lag 1/1/2 on the secondary VSX switch. When a loop occurs, loop protect notifies the secondary VSX switch that a loop is on the network and interface1/1/2 was blocked. When you enter
show interface 1/1/2 on the secondary switch, the output from the command indicates that the interface was blocked by VSX when in fact the loop protect feature blocked the interface to stop the loop.
If you enter
show lacp interfaces on the downstream switch, the forwarding state of the blocked interfaces is displayed as
down, as shown in the following example:
switch(config)# show lacp interfaces
State abbreviations :
A - Active P - Passive F - Aggregable I - Individual
S - Short-timeout L - Long-timeout N - InSync O - OutofSync
C - Collecting D - Distributing
X - State m/c expired E - Default neighbor state
Actor details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr Forwarding
Name Id Pri Pri Key State
------------------------------------------------------------------------------
1/3/1 lag1 130 1 ALFNCD f8:60:f0:06:87:00 65534 1 up
1/3/2 lag1 131 1 ALFNCD f8:60:f0:06:87:00 65534 1 up
1/7/3 lag2 388 1 ALFOE f8:60:f0:06:87:00 65534 2 lacp-block
1/10/46 lag2 623 1 ALFOE f8:60:f0:06:87:00 65534 2 lacp-block
Partner details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr
Name Id Pri Pri Key
------------------------------------------------------------------------------
1/3/1 lag1 206 1 ALFNCD f8:60:f0:06:49:00 65534 1
1/3/2 lag1 1130 1 ALFNCD f8:60:f0:06:49:00 65534 1
1/7/3 lag2 0 65534 PLFOEX 00:00:00:00:00:00 65534 0
1/10/46 lag2 0 65534 PLFOEX 00:00:00:00:00:00 65534 0
Interface
lag2, which was shown as
lacp-blocked in the previous example is shown as
down on the primary VSX switch, as shown in the following example:
switch(config)# show loop-protect
Status and Counters - Loop Protection Information
Transmit Interval : 5 (sec)
Port Re-enable Timer : Disabled
Interface lag1
Loop-protect enabled : Yes
Loop-Protect enabled VLANs : 1-100
Action on loop detection : TX disable
Loop detected count : 1
Loop detected : Yes
Detected on VLAN : 10
Detected at : 2019-09-27T00:12:55
Interface status : up
Interface lag2
Loop-protect enabled : Yes
Loop-Protect enabled VLANs : 2021-2121
Action on loop detection : TX disable
Loop detected count : 1
Loop detected : Yes
Detected on VLAN : 2103
Detected at : 2019-09-27T00:13:14
Interface status : down
switch(config)# show lacp interfaces
State abbreviations :
A - Active P - Passive F - Aggregable I - Individual
S - Short-timeout L - Long-timeout N - InSync O - OutofSync
C - Collecting D - Distributing
X - State m/c expired E - Default neighbor state
Actor details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr Forwarding
Name Id Pri Pri Key State
------------------------------------------------------------------------------
1/4/14 lag1(mc) 206 1 ALFNCD f8:60:f0:06:49:00 65534 1 up
1/5/15 lag2(mc) down
Partner details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr
Name Id Pri Pri Key
------------------------------------------------------------------------------
1/4/14 lag1(mc) 130 1 ALFNCD f8:60:f0:06:87:00 65534 1
1/5/15 lag2(mc)
Interface
lag2 is also shown as
down on the secondary VSX switch, as shown in the following example:
switch(config)# show loop-protect
Status and Counters - Loop Protection Information
Transmit Interval : 5 (sec)
Port Re-enable Timer : 15 (sec)
Interface lag1
Loop-protect enabled : Yes
Loop-Protect enabled VLANs : 1-100
Action on loop detection : TX disable
Loop detected count : 0
Loop detected : No
Interface status : up
Interface lag2
Loop-protect enabled : Yes
Loop-Protect enabled VLANs : 2021-2121
Action on loop detection : TX disable
Loop detected count : 0
Loop detected : No
Interface status : down
switch(config)# show lacp interfaces
State abbreviations :
A - Active P - Passive F - Aggregable I - Individual
S - Short-timeout L - Long-timeout N - InSync O - OutofSync
C - Collecting D - Distributing
X - State m/c expired E - Default neighbor state
Actor details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr Forwarding
Name Id Pri Pri Key State
------------------------------------------------------------------------------
1/3/2 lag1(mc) 1130 1 ALFNCD f8:60:f0:06:49:00 65534 1 up
1/9/3 lag2(mc) down
Partner details of all interfaces:
------------------------------------------------------------------------------
Intf Aggr Port Port State System-ID System Aggr
Name Id Pri Pri Key
------------------------------------------------------------------------------
1/3/2 lag1(mc) 131 1 ALFNCD f8:60:f0:06:87:00 65534 1
1/9/3 lag2(mc)