clear arp-cache

very useful...  arp is a very strong informational, and troubleshooting tool, often overlooked... don't forget to set your service timestamps for debug and log output to datetime...  uptime is a waste of time...

dls1#clear arp-cache                                                                            
dls1#                                                                                           
May  7 18:55:50: IP ARP: sent req src 172.16.100.1 000f.8ffe.0980,                              
                 dst 172.16.100.150 e89a.8f98.a703 Vlan100                                      
May  7 18:55:50: IP ARP: sent req src 172.16.200.1 000f.8ffe.0980,                              
                 dst 172.16.200.2 000b.5fc9.0000 Vlan200                                        
May  7 18:55:50: IP ARP: sent req src 172.16.200.1 000f.8ffe.0980,                              
                 dst 172.16.200.250 984b.e1fb.2940 Vlan200                                      
May  7 18:55:50: IP ARP: sent req src 172.16.1.1 000f.8ffe.0980,                                
                 dst 172.16.1.2 000b.5fc9.0000 Vlan1                                            
May  7 18:55:50: IP ARP: sent req src 172.16.1.1 000f.8ffe.0980,                                
                 dst 172.16.1.101 0009.b73f.ce80 Vlan1                                          
May  7 18:55:50: IP ARP: sent req src 172.16.100.1 000f.8ffe.0980,                              
                 dst 172.16.100.2 000b.5fc9.0000 Vlan100                                        
May  7 18:55:50: IP ARP: sent req src 172.16.1.1 000f.8ffe.0980,                                
                 dst 172.16.1.102 0009.b752.d780 Vlan1                                          
May  7 18:55:50: IP ARP: sent rep src 172.16.1.1 000f.8ffe.0980,                                
                 dst 172.16.1.1 ffff.ffff.ffff Vlan1                                            
May  7 18:55:50: IP ARP: sent rep src 172.16.1.5 0000.0c07.ac01,                                
                 dst 172.16.1.5 ffff.ffff.ffff Vlan1                                            
May  7 18:55:50: IP ARP: sent rep src 172.16.1.5 0000.0c07.ac01,                                
                 dst 172.16.1.5 0100.0ccd.cdcd Vlan1                                            
May  7 18:55:50: IP ARP: sent rep src 172.16.100.1 000f.8ffe.0980,                              
                 dst 172.16.100.1 ffff.ffff.ffff Vlan100                                        
May  7 18:55:50: IP ARP: sent rep src 172.16.100.5 0000.0c07.ac01,                              
                 dst 172.16.100.5 ffff.ffff.ffff Vlan100                                        
May  7 18:55:50: IP ARP: sent rep src 172.16.100.5 0000.0c07.ac01,                              
                 dst 172.16.100.5 0100.0ccd.cdcd Vlan100                                        
May  7 18:55:50: IP ARP: sent rep src 172.16.200.1 000f.8ffe.0980,                              
                 dst 172.16.200.1 ffff.ffff.ffff Vlan200                                        
May  7 18:55:50: IP ARP: sent rep src 172.16.200.5 0000.0c07.ac01,                              
                 dst 172.16.200.5 ffff.ffff.ffff Vlan200                                        
May  7 18:55:50: IP ARP: sent rep src 172.16.200.5 0000.0c07.ac01,                              
                 dst 172.16.200.5 0100.0ccd.cdcd Vlan200                                        
May  7 18:55:50: IP ARP: rcvd rep src 172.16.100.150 e89a.8f98.a703, dst 172.16.100.1 Vlan100   
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.100.150 e89a.8f98.a703, dst 172.16.100
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.100.150, hw: e89a.8f98.a703      
May  7 18:55:50: IP ARP: rcvd rep src 172.16.200.2 000b.5fc9.0000, dst 172.16.200.1 Vlan200     
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.200.2 000b.5fc9.0000, dst 172.16.200.0
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.200.2, hw: 000b.5fc9.0000        
May  7 18:55:50: IP ARP: rcvd rep src 172.16.200.250 984b.e1fb.2940, dst 172.16.200.1 Vlan200   
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.200.250 984b.e1fb.2940, dst 172.16.200
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.200.250, hw: 984b.e1fb.2940      
May  7 18:55:50: IP ARP: rcvd rep src 172.16.1.2 000b.5fc9.0000, dst 172.16.1.1 Vlan1           
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.1.2 000b.5fc9.0000, dst 172.16.1.1 001
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.1.2, hw: 000b.5fc9.0000          
May  7 18:55:50: IP ARP: rcvd rep src 172.16.1.101 0009.b73f.ce80, dst 172.16.1.1 Vlan1         
May  7 18:55:50: IP                                                                             
dls1# ARP: ignored gratuitous arp src 172.16.1.101 0009.b73f.ce80, dst 172.16.1.1 000f.8ffe.09801
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.1.101, hw: 0009.b73f.ce80        
May  7 18:55:50: IP ARP: rcvd rep src 172.16.100.2 000b.5fc9.0000, dst 172.16.100.1 Vlan100     
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.100.2 000b.5fc9.0000, dst 172.16.100.0
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.100.2, hw: 000b.5fc9.0000        
May  7 18:55:50: IP ARP: rcvd rep src 172.16.1.102 0009.b752.d780, dst 172.16.1.1 Vlan1         
May  7 18:55:50: IP ARP: ignored gratuitous arp src 172.16.1.102 0009.b752.d780, dst 172.16.1.1 1
May  7 18:55:50: IP ARP: creating entry for IP address: 172.16.1.102, hw: 0009.b752.d780        
dls1#                                                                                           
May  7 18:56:05: IP ARP: rcvd req src 172.16.100.150 e89a.8f98.a703, dst 172.16.100.5 Vlan100   
May  7 18:56:05: IP ARP: sent rep src 172.16.100.5 0000.0c07.ac01,                              
                 dst 172.16.100.150 e89a.8f98.a703 Vlan100