Description

This article describes Proxy-arp feature behavior when the feature is set with storm control. 

Symptoms

+------------------------------------------+
|                 QFX5K-#001               |  lo0: 10.100.254.10/32
+------------------------------------------+
                      | xe-0/0/3 
                      |
                      |
                      |
                      | xe-0/0/4 
+------------------------------------------+ 
|               QFX5K-#002(DUT)            | 
+------------------------------------------+ 
                      | ge-0/0/1            10.100.17.2/25 with proxy-arp enable
                      |
                      |
                      |
                      | ge-0/0/1            10.100.17.129/16
+------------------------------------------+
|                 QFX5K-#003               | 
+------------------------------------------+

Proxy-arp feature does not work as expected when the feature is set with storm control. 

set interfaces irb unit 18 proxy-arp restricted    <<< Proxy arp enable
set interfaces irb unit 18 family inet address 10.100.17.2/25 vrrp-group 17 virtual-address 10.100.17.1
set interfaces irb unit 18 family inet address 10.100.17.2/25 vrrp-group 17 priority 105
set interfaces irb unit 18 family inet address 10.100.17.2/25 vrrp-group 17 preempt
set interfaces irb unit 18 family inet address 10.100.17.2/25 vrrp-group 17 accept-data
set interfaces ge-0/0/1 unit 0 family ethernet-switching storm-control default.  <<< storm-control enable
 

Ping is failed on  QFX5K-#003       

labroot@qfx003> ping 10.100.254.10   
PING 10.100.254.10 (10.100.254.10): 56 data bytes.

Solution

In the current scenario, when both storm-control and Proxy-ARP are enabled simultaneously, packets are dropped in hardware due to the SwitchToCpuCancel ACTION of the sc-arp-filter, which is installed alongside the storm control filter.

This issue matches the following JUNOS.
JUNOS:21.3R3, 21.4R3, 22.1R2, 22.2R1, 22.3R1 

WORKAROUND: 

If the Storm Control is necessary for the configuration, Proxy-ARP configuration can be discarded.

NOTE: 

However, in releases that include the fix for PR 1824023, Proxy-ARP and Storm Control are expected to function together without issues.

Fixed versions of PR 1824023 (https://prsearch.juniper.net/problemreport/PR1824023) :

junos:21.4R3-S9 junos:22.2R3-S5 junos:22.4R3-S4 junos:23.2R2-S2 junos:23.4R2-S3 junos:24.2R2 junos:24.3R1 junos:24.4R1

Modification History

2023/07/23:<KB created>
2023/09/08:<modify to change visibility>

2025/03/10 > Proxy ARP and Storm Control are expected to function together seamlessly in releases having fix of PR 1824023.