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Reminding - ARP. Two machines on a given network can communicate only if they know each other’s physical network address ARP (Address Resolution Protocol) serves for mapping from high-level IP address into low level MAC address. 10.4.10.91 00:11:22:33:44:55:bc. Reminding – ARP.
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Reminding - ARP • Two machines on a given network can communicate only if they know each other’s physical network address • ARP (Address Resolution Protocol) serves for mapping from high-level IP address into low level MAC address.
10.4.10.91 00:11:22:33:44:55:bc Reminding – ARP ARP Response (00:11:22:33:44:55:12) ARP Request (10.4.10.90) 10.4.10.90 00:11:22:33:44:55:12 10.4.10.86 00:11:22:33:44:55:2e 10.4.10.20 00:11:22:33:44:55:6b 10.4.10.23 00:11:22:33:44:55:40
Proxy ARP • Proxy ARP (also called promiscuous ARP or ARP hack) is a technique used to map a single IP network prefix into two physical addresses. • Using the same network address space for more than one physical address • Assume that there are 2 networks A and B connected by router R that runs Proxy ARP • Using Proxy ARP, R can use the same net id for both networks.
10.10.1.5 10.10.1.3 10.10.1.4 Proxy ARP Network A: 10.10.1.x/24 R PPP . Network B: 10.10.1.x/24
Proxy ARP • Router R replies to ARP requests that are generated by hosts on the PPP connection (Network B), in which the target IP is on network A, namely it sends its MAC address. • R know which hosts are connected through the PPP. • These host assume that the destination host are on the same physical network. • In their ARP table the router MAC address is associated with the destination IP address.