It sounds like your problem is related to DHCP and not ARP. If the MAC isn't that of the host you're working with, do a " show mac-address-table | inc " This will tell you to which physical port the machine with the offending duplicate IP is connected.Ĭlear arp-cache - Clears layer 3 ARP entries routing to or through the switch itself (doesn't affect layer 2 traffic traversing the switch on a single VLAN).Ĭlear mac address-table dynamic - Clears layer 2 bindings of MAC addresses to ports.īoth of these are ok to run on a production switch, you'll lose at most one packet per flow. Look at the ARP entry for the IP in question. Might someone have configured a static ARP entry for different hardware at some point? You say "the address" is stuck in the ARP table? What address? The MAC of the PC? The IP you're assigning via DHCP? Can you post specific examples of what you think is stuck in error and why?ĭoes the MAC stuck in the ARP table for the IP match the MAC of the computer? It's possible that another device is causing an IP conflict. No firewall at location.ĪRP entries are cached for several minutes.
#REASON FOR MAC ADDRESSES PC#
Even when we shut the PC in question down, the address remains in the arp table. We have restarted the the DHCP server, 1335, and PC. The address is stuck in the arp table and is unable to resolve mac address. Does not obtain an address or resolve the mac address when I remove port security. 1) A malicious actor somehow spoofing MAC addresses on your internal network, or (much more likely) 2) A computer on your network has some type of virtual (VPN, Virtual Machine, Docker Container, Internet Connection Sharing, etc) adapter (s) which are registering with your router as they show up in the subnet's ARP table. PC was unable to successfully negotiate an address. If there is a response, the IP to MAC mapping will show in the address table for the system ARP timeout. When traffic comes to the router destined for that IP, an ARP packet is broadcast at layer 2, "Who has IP tell " If there is no response, the IP address shows up as unresolved. If you ping an IP on that subnet that doesn't exist at all and then do sho mac address-table you will see it as unresolved.Īn IP address is a layer 3 address.
#REASON FOR MAC ADDRESSES FREE#
I tried both commands listed to free up the ip addresses, but the moment we turned the PCs back on, the IP address returns with an unresolved MAC address. There is no MAC address just the IP address. The IP address of the workstation is what is stuck in the ARP table, even after the PC is turned off, with a message in the sho mac address-table stating that the MAC address is unresolved.
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