The C6  answer to another ip for wan port  in case on unicast flood the switch forget the mac address of 185.8.66.90 and act like a hub.

and there for it hangs the C6 for severals seconds

Legacy ping  from 46.227.16.12 (74:83:ef:96:1b:e0) > 185.8.66.90 (d0:27:88:b1:c8:33)

In bold the bad answer

11:38:36.803701 74:83:ef:96:1b:e0 > d0:27:88:b1:c8:33, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805173 d0:27:88:b1:c8:33 > 74:83:ef:96:1b:e0, ethertype IPv4 (0x0800), length 98: 185.8.66.90 > 46.227.16.12: ICMP echo reply, id 40551, seq 29, length 64
11:38:36.805429 ac:15:a2:b3:ba:53 > 74:83:ef:96:1b:e0, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805429 30:de:4b:27:b0:19 > 70:b3:d5:e6:10:78, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805429 74:83:ef:96:1b:e0 > d0:27:88:b1:c8:33, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805429 ac:15:a2:b3:be:ca > 74:83:ef:96:1b:e0, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805429 74:83:ef:96:1b:e0 > d0:27:88:b1:c8:33, ethertype IPv4 (0x0800), length 98: 46.227.16.12 > 185.8.66.90: ICMP echo request, id 40551, seq 29, length 64
11:38:36.805430 ac:15:a2:b3:bf:09 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 185.8.66.90 tell 185.8.66.81, length 46
11:38:36.806974 d0:27:88:b1:c8:33 > 74:83:ef:96:1b:e0, ethertype IPv4 (0x0800), length 98: 185.8.66.90 > 46.227.16.12: ICMP echo reply, id 40551, seq 29, length 64
11:38:36.806974 d0:27:88:b1:c8:33 > 74:83:ef:96:1b:e0, ethertype IPv4 (0x0800), length 98: 185.8.66.90 > 46.227.16.12: ICMP echo reply, id 40551, seq 29, length 64