no ip proxy-arp

Advantages of Proxy ARP

The main advantage of proxy ARP is that it can be added to a single router on a network and does not disturb the routing tables of the other routers on the network.
Proxy ARP must be used on the network where IP hosts are not configured with a default gateway or do not have any routing intelligence.

Disadvantages of Proxy ARP

Hosts have no idea of the physical details of their network and assume it to be a flat network in which they can reach any destination simply by sending an ARP request. But using ARP for everything has disadvantages. These are some of the disadvantages:

• It increases the amount of ARP traffic on your segment.
• Hosts need larger ARP tables in order to handle IP-to-MAC address mappings.
• Security can be undermined. A machine can claim to be another in order to intercept packets, an act called "spoofing."
• It does not work for networks that do not use ARP for address resolution.
• It does not generalize to all network topologies. For example, more than one router that connects two physical networks.