CCNP TSHOOT 6.0 - Cisco Learning Home

CCNPv6 TSHOOT
• Address Resolution Protocol (ARP) failures. After clearing the ARP cache and triggering a connection
attempt (for instance, by using ping), ARP entries show up as incomplete or are missing.
• Packets are not being received, which is shown by using a packet sniffer on the receiving host.
Confirm or Deny Layer 3 Connectivity
DLS1#ping 10.1.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.2.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
DLS1#clear arp-cache
DLS1#show arp
Protocol Address Age (min) Hardware Addr Type Interface
Internet 10.1.10.1 0 0007.e963.ce53 ARPA Vlan10
Internet 10.1.2.1 - 0017.5a5b.b442 ARPA FastEthernet0/5
Internet 10.1.50.1 0 0007.e963.ce53 ARPA Vlan50
Internet 10.1.100.1 0 001b.0c6d.8f41 ARPA Vlan100
Internet 10.1.100.254 - 0000.0c07.ac64 ARPA Vlan100
Internet 10.1.100.253 0 0017.5a53.a3c1 ARPA Vlan100
Internet 10.1.100.252 - 0017.5a5b.b441 ARPA Vlan100
Internet 10.1.50.252 - 0017.5a5b.b446 ARPA Vlan50
Internet 10.1.50.254 - 0000.0c07.ac32 ARPA Vlan50
Internet 10.1.20.252 - 0017.5a5b.b444 ARPA Vlan20
Internet 10.1.30.252 - 0017.5a5b.b445 ARPA Vlan30
Internet 10.1.10.252 - 0017.5a5b.b443 ARPA Vlan10
The most relevant fields in the output are the IP address, hardware address, and interface fields, because these
give you the essential information that you are usually looking for when you issue the show arp command.
The age field is also relevant. By default, ARP entries are cached for four hours. To make sure that you are
looking at current information, you can use the clear arp-cache command to flush existing entries from the
cache.
If there is a “-” in the age field instead of a number, this entry is local to the switch. These entries represent locally
configured IP and MAC addresses, and the switch will respond to ARP requests for these entries.
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