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In order to enable proxy ARP on an interface, issue the ip proxy-arp interface configuration command. Proxy ARP can be disabled on each interface individually with the interface configuration command no ip proxy-arp, as shown: Router# configure terminalĮnter configuration commands, one per line. The no ip proxy-arp command must be configured on the interface of the router connected to the ISP router. The interface of the Cisco must be configured to accept and respond to proxy ARP. #Tu portal prxy access menu mac#Note: Multiple IP addresses are mapped to a single MAC address, the MAC address of this router, which indicates that proxy ARP is in use. The ARP cache of Host A is shown in this table: IP Address The router forwards those packets to the hosts in Subnet B. Hence, all packets destined to Subnet B are sent to the router. The ARP cache on the hosts in Subnet A is populated with the MAC address of the router for all the hosts on Subnet B. #Tu portal prxy access menu how to#Since the router knows how to reach Host D, the router forwards the packet to Host D. Upon receipt of this ARP reply, Host A updates its ARP table, as shown: IP Addressįrom now on, Host A forwards all the packets that it wants to reach 172.16.20.200 (Host D) to the MAC address 00-00-0c-94-36-ab (router). The ARP replies are always unicast to the original requester. The proxy ARP reply packet is encapsulated in an Ethernet frame with MAC address of the router as the source address and the MAC address of Host A as the destination address. This is the Proxy ARP reply that the router sends to Host A. Since the router knows that the target address (172.16.20.200) is on another subnet and can reach Host D, it replies with its own MAC address to Host A. The broadcast does not reach Host D because routers, by default, do not forward broadcasts. Since the ARP request is a broadcast, it reaches all the nodes in the Subnet A, which includes the e0 interface of the router, but does not reach Host D. The ARP request packet is then encapsulated in an Ethernet frame with the MAC address of Host A as the source address and a broadcast () as the destination address. Therefore, Host A broadcasts an ARP request on Subnet A, as shown: Sender's MAC Address In order to reach Host D (172.16.20.200), Host A needs the MAC address of Host D. Therefore, when Host A needs to send a packet to Host D, Host A believes that Host D is directly connected, so it sends an ARP request to Host D. When Host A needs to communicate with any devices it believes are directly connected, it sends an ARP request to the destination. ![]() What this means is that Host A believes that it is directly connected to all of network 172.16.0.0. As shown in the diagram, Host A has a /16 subnet mask. ![]() This is an example of how proxy ARP works: Network Diagram Refer to Cisco Technical Tips Conventions for more information on document conventions. If you are working in a live network, ensure that you understand the potential impact of any command before using it. All of the devices used in this document started with a cleared (default) configuration. The information presented in this document was created from devices in a specific lab environment. #Tu portal prxy access menu software#The information in this document is based on these software and hardware versions: This document requires an understanding of the ARP and Ethernet environment. ![]() Proxy ARP can help machines on a subnet reach remote subnets without the need to configure routing or a default gateway. By "faking" its identity, the router accepts responsibility for routing packets to the "real" destination. Proxy ARP is the technique in which one host, usually a router, answers ARP requests intended for another machine. This document explains the concept of proxy Address Resolution Protocol (ARP). ![]()
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