Router is sending unsolicited ICMP echo replies at regular intervals

Hi,

I have observed our NE20E sending unsolicited ICMP echo replies at regular intervals. The source and destination IP addresses are that of the router, but the destination MAC address is that of a connected device. Why is the router doing this? 

tcpdump:listening on eth2.99, link-type EN10MB (Ethernet), capture size 262144 bytes

17:16:40.26157634:1e:6b:1b:ca:ff > 00:1b:21:5f:2e:d3, ethertype IPv4 (0x0800), length 78:(tos 0xe0, ttl 2, id 0, offset 0, flags [none], proto ICMP (1), length 64)

   172.19.11.20 > 172.19.11.20: ICMPecho reply, id 65535, seq 0, length 44

17:16:41.26592034:1e:6b:1b:ca:ff > 00:1b:21:5f:2e:d3, ethertype IPv4 (0x0800), length 78:(tos 0xe0, ttl 2, id 0, offset 0, flags [none], proto ICMP (1), length 64)

   172.19.11.20 > 172.19.11.20: ICMPecho reply, id 65535, seq 0, length 44

17:16:42.26220934:1e:6b:1b:ca:ff > 00:1b:21:5f:2e:d3, ethertype IPv4 (0x0800), length 78:(tos 0xe0, ttl 2, id 0, offset 0, flags [none], proto ICMP (1), length 64)

   172.19.11.20 > 172.19.11.20: ICMPecho reply, id 65535, seq 0, length 44

17:16:43.27023934:1e:6b:1b:ca:ff > 00:1b:21:5f:2e:d3, ethertype IPv4 (0x0800), length 78:(tos 0xe0, ttl 2, id 0, offset 0, flags [none], proto ICMP (1), length 64)

   172.19.11.20 > 172.19.11.20: ICMPecho reply, id 65535, seq 0, length 44

17:16:44.26528434:1e:6b:1b:ca:ff > 00:1b:21:5f:2e:d3, ethertype IPv4 (0x0800), length 269:(tos 0xe0, ttl 2, id 0, offset 0, flags [none], proto ICMP (1), length 255)

   172.19.11.20 > 172.19.11.20: ICMPecho reply, id 65535, seq 0, length 235

HuaweiVersatile Routing Platform Software
VRP (R) software, Version 8.180 (NE20E V800R010C10SPC500)
Copyright (C) 2012-2018 Huawei Technologies Co., Ltd.
HUAWEI NE20E-S4 uptime is 198 days, 1 hour, 26 minutes 
Patch Version: V800R010SPH052

Thank you in advance.