Chapter 24 Arp Local Proxy Configuration; Introduction To Arp Local Proxy Function - Edge-Core ES4624-SFP Basic Management Manual

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Chapter 24 Arp local proxy

Configuration

In a real application environment, the switches in the aggregation layer are required

to implement local arp proxy function to avoid arp cheating. This function will restrict the

forwarding of arp messages in the same vlan and thus direct the L3 forwarding of the

data flow through the switch.

As shown in the figure above, PC1 wants to send an IP message to PC2, the overall

procedure goes as follows (some non-arp details are ignored)

1. since PC1 does not have the arp of PC2, it sends and broadcasts ARP request.

2. Receiving the arp message, the switch hardware will send the arp request to CPU

instead of forwarding this message via hardware, according to new arp handling rules.

3. With local arp proxy enabled, the switch will send arp reply message to PC1 (to fill

up its mac address)

4. After receiving the arp reply, PC1 will create arp, send an IP message, and set

the destination MAC of the Ethernet head as the MAC of the switch.

5. After receiving the ip message, the switch will search the router table (to create

router cache) and distribute hardware entries.

6. If the switch has the arp of PC2, it will directly encapsulate the Ethernet head and

send the message (the destination MAC is that of PC2)

7. if the switch does not have the arp of PC2, it will request it and then send the ip

192.168.1.100

192.168.1.200

Troubleshooting