How does DHCP Server "Ping IP when allocating new IP" work?

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How does DHCP Server "Ping IP when allocating new IP" work?

L0 Member

What's the destination MAC address when this ping is sent?

When is this ping sent?  After/Before DHCP requests?

Thanks.

1 REPLY 1

L6 Presenter

Just guessing here but:

1) ARP-WHOHAS is sent... (unless its reachable through some nexthop because then the 2) below is sent to this nexthop).

2) If someone replies to above (could be some proxyarp or so) an icmp echo request is sent to the mac (unless its routed through some nexthop).

3) If echo reply (or administratively prohibited) is returned the box assumes this ip is already taken.

Someone from PA who could confirm? 🙂

The downside would be if you have a personal/desktop firewall who blocks incoming echo requests...

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