Operation Manual – ARPH3C S7500 Series Ethernet Switches Chapter 1 ARP Configuration1-5virtual routers to update the ARP entries on the device that is connected to the switchand incapable of updating ARP entries actively.If a small number of VLAN interfaces and VRRP backup groups are configured, it takesa very time for the device to traverse all the VLAN interfaces and their IP addresses. Ifthe traffic loops without being limited, gratuitous ARP packets are sent to the same IPaddress at an interval too short. This increases switch work load and network traffic. Tosolve this problem, the device allows you to configure the gratuitous ARP updateinterval.1.1.6 Introduction to ARP Attack DetectionIf an attacker sends an ARP message with a fake source IP address to a gateway, thegateway adds the IP-to-MAC mapping into its ARP mapping table. The attacker maysend ARP messages with all the IP addresses of the network segment as the source IPaddresses to the gateway, causing other devices unable to access the network.To guard against such attacks, S7500 series Ethernet switches support the ARP attackdetection feature. With this feature, you can limit the number of IP addresses to bebound to a MAC address in a VLAN. If a MAC address is bound to more than thespecified number of IP addresses, it is considered an attacking MAC address.Consequently, all the ARP messages containing the attacking MAC address as thesource MAC address will be discarded unless the ARP request is sent from the localdevice.1.1.7 Introduction to Proxy ARPThe proxy ARP function allows devices to forward ARP requests between host indifferent networks and ARP requests from one host in a network to another host on anisolated port in the same network, so as to provide Layer 3 connectivity between Layer2 isolated ports.To provide Layer 3 connectivity between ports in the following conditions, you need toenable the proxy ARP function.z Super VLAN function is enabled on the S7500 switch.z The isolate-user-vlan function is enabled on Layer 2 switches connecting with theS7500 switch.
