Alcatel-Lucent OmniSwitch 10K - Page 38

OmniSwitch OS6860/OS6900/OS10K Troubleshooting Guide Part No.032996-00 Rev.A
AOS Release 7.X and 8.X January 2015
Alcatel-Lucent Page 38 of 148
Mac Address: & = duplicate static address,
Domain Vlan/SrvcId/ISId Mac Address Type Operation Interface
-----------+---------------------+-------------------+---------------+------------+----------
VLAN 10 00:13:72:19:5e:1f dynamic bridging 1/1/15
This output shows that MAC address 00:13:72:19:5e:1f, belonging to SRC, is learned on port
1/1/15 in VLAN 10.
To obtain the MAC address required for forwarding a datagram, the layer 3 switch does the following:
 First, the layer 3 switch looks in the ARP cache for an entry that lists the MAC address for the IP
address. The ARP cache maps IP addresses to MAC addresses. The cache also lists the port attached
to the device. A dynamic ARP entry enters the cache when the Layer 3 switch receives an ARP reply.
 If the ARP cache does not contain an entry for the destination IP address, the Layer 3 switch
broadcasts an ARP request out all its IP interfaces. The ARP request contains the IP address of the
destination. If the device with the IP address is reachable by the Layer 3 switch, the device sends an
ARP response containing its MAC address. The response is a unicast packet addressed directly to the
layer 3 switch. The layer 3 switch places the information from the ARP response into the ARP cache.
To search for a specific ARP entry, use the following command syntax:
show arp <ip-address>
OS6860-VCof4-> show arp 10.255.13.26
Total 22 arp entries
Flags (P=Proxy, A=Authentication, V=VRRP, R=REMOTE, B=BFD, H=HAVLAN, I=INTF)
IP Addr Hardware Addr Type Flags Port Interface Name
-----------------+-------------------+----------+-------+--------+-----------+----------
10.255.13.26 08:00:20:a8:f0:8a DYNAMIC 1/1/47 vlan-172
To search for an ARP entry associated with a MAC address use the following command syntax:
show arp <mac-address>
For example:
OS6860-VCof4-> show arp 08:00:20:a8:f0:8a
Total 20 arp entries
Flags (P=Proxy, A=Authentication, V=VRRP, R=REMOTE, B=BFD, H=HAVLAN, I=INTF)
IP Addr Hardware Addr Type Flags Port Interface Name
-----------------+-------------------+----------+-------+--------+-----------+-------------------
10.255.13.26 08:00:20:a8:f0:8a DYNAMIC 1/1/47 vlan-172
Common Error Conditions
If an ARP is not getting resolved, the following conditions may exist:
• A problem with the general health of the switch or NI.
• Physical link status might not be operational.
• MAC address not learned on the port.
• ARP request not reaching the switch, which may be because:
- The workstation is not sending an ARP reply.
- The workstation is not able to understand the ARP request.
- The ARP response might have been corrupted.