Plusnet Hub Manager - Event Log

[#1]

Left my router on whilst away but it states up time as 4 days, so looked at event log and cannot understand the following (and a lot seem to be because of ICMP replay) simple explanation would be appreciated please.

OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>157.240.1.23 on ppp3)
16:06:01, 25 Jun.	BLOCKED 5 more packets (because of ICMP replay)
16:05:57, 25 Jun.	OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>157.240.1.23 on ppp3)
16:05:40, 25 Jun.	BLOCKED 1 more packets (because of ICMP replay)
16:05:38, 25 Jun.	OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>213.161.77.83 on ppp3)
16:05:32, 25 Jun.	OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>213.161.77.102 on ppp3)
16:05:26, 25 Jun.	OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>216.58.198.179 on ppp3)
16:05:24, 25 Jun.	BLOCKED 1 more packets (because of ICMP replay)
16:05:19, 25 Jun.	OUT: BLOCK [7] ICMP replay (ICMP type 3 code 1 51.6.141.226-​>216.58.198.179 on ppp3)

[#2]

I am seeing a lot of these too (only since the start if the week oddly). No idea why they are happening but I suspect my TP-Link Deco Mesh network may have something to do with it as AFAIK ICMP Replay is where some sort of ICMP packet is sent again by a different device (almost as though it is spoofed, but not necessarily). All of the devices on my network sit on the Deco Mesh and the PN Hub is working in a pseudo modem-only mode.

[#3]

I've also noticed a lot of these, it appears that most of them are directed toward Microsoft Office 365 servers, so I assume it's legitimately Windows 10 and/or Office 365 apps trying to check on the infrastructure. I'm not sure if blocking them has any detrimental affect on the PC's or router's performance?

http://download.priasoft.com/office365/Office365_EndPoints.html