4 ms·

A couple of weeks ago I had a customer router which wouldn't update its ARP table unless a system performed exactly the IPv4 Duplicate Address Detection "Probe"

A couple of weeks ago I had a customer router which wouldn't update its ARP table unless a system performed exactly the IPv4 Duplicate Address Detection "Probe" and "Announcement" steps defined in RFC-5227: https://www.rfc-editor.org/rfc/rfc5227.html https://www.rfc-editor.org/rfc/rfc5227.html Even for failover of a cluster VIP, which is needlessly strict. That's the strangest ARP behaviour I've seen in a while. Also, if you're on Azure, setup two VMs in the same subnet and watch ARP between them. They actually aren't in the same subnet and there's something doing Proxy ARP between them with a MAC like 01:23:45:67:89:AB or something like that. Cursed.

nousermane 4y ago
Azure network is junk. Try running traceroute from a VM running there - it will come back empty. They just silently drop ICMP "TTL expired" packets, for "security" reasons, no doubt. Also, you can't spoof source IP there, even when talking between your VMs on a private subnet. So forget about running a router inside a VM. On AWS you can. [0] [0] https://docs.aws.amazon.com/vpc/latest/userguide/VPC_NAT_Instance.html#EIP_Disable_SrcDestCheck https://docs.aws.amazon.com/vpc/latest/userguide/VPC_NAT_Ins...
- suprjami 4y ago
  > Azure network is junk. We haven't even got to the joys of the load balancer yet! Just log onto the VM console to troubleshoot. Oh, they don't have a console by design, okay then.
- grepfru_it 4y ago
  >So forget about running a router inside a VM How does VyOS do it? https://docs.vyos.io/en/equuleus/installation/cloud/azure.html https://docs.vyos.io/en/equuleus/installation/cloud/azure.ht...