Why Does One Interface of the Vwire Pair Show "power-down"?

Why Does One Interface of the Vwire Pair Show "power-down"?

14090
Created On 04/07/19 13:07 PM - Last Modified 04/08/19 16:41 PM


Question
Why does one interface of the virtual wire pair shows power-down?
> show interface all 
<snip>
ethernet1/5             20    ukn/ukn/down(power-down)  00:1b:17:6b:e0:14 
<snip>


Environment
System with at least one set of interfaces in a virtual wire pair.

Answer
In vwire pair interfaces, link-state pass through is enabled by default.
When one interface goes down, PAN-OS powers down the other link of the vwire pair due to link-state pass through.
 
> show interface all 
<snip>
ethernet1/4   19    ukn/ukn/down(autoneg)     00:1b:17:6b:e0:13  <<< Interface that is down due to physical link down
ethernet1/5   20    ukn/ukn/down(power-down)  00:1b:17:6b:e0:14  <<< Interface powered down by PAN-OS
<snip>


Alternatively, you can check the system logs Web Interface:

webgui-systemlogs

CLI:
user@firewall> show log system direction equal backward eventid equal link-change
Time                Severity Subtype Object EventID ID Description
===============================================================================
2019/04/07 05:40:44 info     port    ethern link-ch 0  Port ethernet1/4: Down 1Gb/s-full duplex


The system log, only logs the interface that physically goes down. For more information, please refer to the following articles:
https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClqMCAS
https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClzQCAS

brdagent log can also be checked:
admin@firewall> less dp0-log brdagent.log  

2019-04-07 05:40:44.600 -0700 Port  4: (port_linked) PHY shows down, val 0x7949
2019-04-07 05:40:44.601 -0700 Port  4: Down 1Gb/s-full duplex
2019-04-07 05:40:44.602 -0700 PORT4: board_port_autoneg_enabled -> board_port_autoneg, link: 0, mode: 1
2019-04-07 05:40:44.620 -0700 Port  5: POWERDOWN command received <<<
2019-04-07 05:40:44.621 -0700 PORT5: board_port_autoneg_enabled -> board_port_powerdown, link: 0, mode: 1
2019-04-07 05:40:44.621 -0700 Port  5: Powered down

"POWERDOWN command received" indicates the brdagent received command from mprelay to power down the interface.

mprelay log can be checked for reasons that show the interface going down.

First ethernet1/4 link down is detected and immediately link-state-pass-through is detected:
admin@firewall> less dp0-log mprelay.log 

2019-04-07 05:40:44.608 -0700 Interface ethernnet1/4 link down, changed from cached state: yes
2019-04-07 05:40:44.608 -0700 IFMon: vwire interface ethernet1/4 link down, check link-state-pass-through

Then the ethernet1/5 is set to down:
2019-04-07 05:40:44.609 -0700 Set vwire interface ethernet1/5 link state to down
2019-04-07 05:40:44.609 -0700 get interface link properties: name ethernet1/5
2019-04-07 05:40:44.617 -0700 Interface ethernet1/5 current state, speed 3 duplex 2 link 1
2019-04-07 05:40:44.617 -0700 set interface link properties: name ethernet1/5 speed auto duplex auto state down disable no
2019-04-07 05:40:44.624 -0700 IFMon: post event interface ethernet1/4 link down
2019-04-07 05:40:44.624 -0700 IFMon: scheduled link-passthrough scan at 15 seconds later
2019-04-07 05:40:44.625 -0700 IFMon: sys.s1.p5.status changed
2019-04-07 05:40:44.625 -0700 Interface ethernnet1/5 link down, changed from cached state: no
2019-04-07 05:40:44.625 -0700 Interface 5 mode changed from 1 to 3
2019-04-07 05:40:44.625 -0700 Interface 5, if_admin_mode_mask=0x30


Once the interface that is physically brought up, the powered down interface is powered up.

mprelay log:
2019-04-07 06:02:56.175 -0700 IFMon: sys.s1.p4.status changed
2019-04-07 06:02:56.176 -0700 Interface ethernnet1/4 link up, changed from cached state: yes
2019-04-07 06:02:56.176 -0700 IFMon: vwire interface ethernet1/4 link up, check link-state-pass-through
2019-04-07 06:02:56.176 -0700 Set vwire interface ethernet1/5 link state to up


bradagent log:
2019-04-07 06:02:56.176 -0700 PORT4: board_port_autoneg -> board_port_autoneg_linked, link: 1, mode: 1
2019-04-07 06:02:56.176 -0700 Port  4: Up   1Gb/s-full duplex
2019-04-07 06:02:56.179 -0700 Port  4: MAC enabled
2019-04-07 06:02:56.179 -0700 PORT4: board_port_autoneg_linked -> board_port_autoneg_enabled, link: 1, mode: 1
2019-04-07 06:02:56.187 -0700 Port  5: AUTONEG command received
2019-04-07 06:02:56.187 -0700 PORT5: board_port_powerdown -> board_port_reset, link: 0, mode: 3
2019-04-07 06:02:56.187 -0700 Port  5: Power up


 


Additional Information

What is link-state pass through? 
https://docs.paloaltonetworks.com/pan-os/7-1/pan-os-web-interface-help/network/network-virtual-wires

How to enable/disable link-state pass through?
https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClMiCAK

 



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