Fault Symptom
PC1 and PC2 reside on the same network segment 192.168.0.0/16. The two routers have static routes to the network segment of each other.
After the configuration is complete, PC1 fails to ping PC2.
Fault Analysis
1. Run the arp -a command on PC1 to check all ARP entries. You can find that there is no mapping between the IP address and MAC address of PC2. It indicates that the ARP entry is not learned when the ping command is run. When Router A receives the ARP Request packet from PC1, it finds that the destination IP address in the packet is not the IP address of the local interface. Therefore, Router A discards the ARP Request packet.
Procedure
1. Run the system-view command to enter the system view on RouterA (or RouterB).
2. Run the interface interface-type interface-number command to enter the view of the customer-facing interface.
3. Run the arp-proxy enable command to enable routed proxy ARP on the interface.
4. Run the ping 192.168.2.2 command on PC1 to ping the IP address of PC2. Then, run the arp -a command on PC1. You can find that the MAC address corresponding to the IP address of PC2 is the MAC address of the interface connected to PC1 on RouterA.
C:\Documents and Settings\Administrator>arp -a
Interface: 192.168.1.2 --- 0x2
Internet Address Physical Address Type
192.168.2.2 00e0-fc39-80aa dynamic
When the configuration is complete, PC1 can successfully ping PC2, and the fault is rectified.
Summary
Proxy ARP is a technique by which a device serving as a proxy on a given network answers the ARP requests for a network address that is not on that network. There are three proxy ARP modes that can be applied in different situations:
· Routed proxy ARP: enables the communications between computers on the same network segment but on different physical networks.
· Proxy ARP within a VLAN: enables the communications between computers within a VLAN configured with user isolation.
· Proxy ARP between VLANs: enables Layer 2 communications between computers in different VLANs.
