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ICMP is required for IPv4 to work correctly, too. It's often completely blocked by cargo culting net admins who then wonder why their things fail that ICMP woul
by kstrauser 2y ago
ICMP is required for IPv4 to work correctly, too. It's often completely blocked by cargo culting net admins who then wonder why their things fail that ICMP would have fixed.
- jiggawatts 2y agoI have a laundry list of issues like this: Firewalls stopped sending RST packets (or any other kind of error) by default on all ports more than a decade ago. This is great for Internet-facing security, but has converted from easily diagnosed instant failures on internal networks to 30 second timeouts... which are indistinguishable from "host is down". Don't worry! Just ping the host... err... can't do that either because of overly paranoid admins like you mentioned. Next, spend a week trying to figure out why packets seem to go only one way through a cloud VPN only to discover that Path MTU Discovery uses ICMP and without which VPNs are basically broken. Fun.