How to Clear the Windows ARP Cache using the arp -d Command

The Address Resolution Protocol Cache

In a Windows network environment, computers do not communicate using IP addresses at the lowest hardware level; they use MAC (Media Access Control) addresses. When your Windows machine wants to send a packet to a local server at 192.168.1.50, it checks its internal ARP (Address Resolution Protocol) cache to see if it knows the MAC address associated with that IP.

If a network administrator replaces a failing router or moves a server to a new physical network card, the IP address might remain the same, but the MAC address has changed. If your Windows workstation holds onto the old, stale ARP cache entry, it will continue sending packets into a black hole, resulting in a “Destination Host Unreachable” error, even if the server is clearly online.

To fix this specific layer-2 networking issue, you must forcefully clear the Windows ARP cache.

Viewing the Current Cache

Before clearing the cache, you can view its current contents using the arp command. Open a standard Command Prompt (or PowerShell) and type:

arp -a

This will dump a table showing every IP address your computer has recently communicated with, along with its mapped physical MAC address, and whether the entry is dynamic (learned over the network) or static (hardcoded).

Interface: 192.168.1.100 --- 0x4
  Internet Address      Physical Address      Type
  192.168.1.1           a0-b1-c2-d3-e4-f5     dynamic
  192.168.1.50          11-22-33-44-55-66     dynamic

Clearing the Cache using arp -d

To purge the cache, you must use the -d (delete) flag. Because manipulating the low-level network stack can disrupt active connections, Windows requires elevated privileges to perform this action.

You must open Command Prompt or PowerShell as an Administrator. Run the following command to delete all wildcard entries across all network interfaces:

arp -d *

The command executes silently. If you immediately run arp -a again, you will see a significantly shorter list containing only a few multicast addresses. The dynamic cache is completely wiped.

Deleting a Specific Entry

If you are managing a massive Windows Server with hundreds of active connections, running a wildcard delete might cause a momentary spike in network latency as the server broadcasts ARP requests to re-learn every MAC address on the subnet.

Instead of a wildcard, you can target a specific IP address. If you know the router at 192.168.1.1 was just swapped out, you can delete only that entry:

arp -d 192.168.1.1

The next time Windows attempts to ping the router, it will recognize that the cache entry is missing, broadcast a fresh “Who has 192.168.1.1?” request to the switch, and instantly record the brand-new MAC address, restoring connectivity.