Dell Force10 MXL Blade MXL 10/40GbE Switch IO Module Configuration Guide - Page 272

www.dell.com | support.dell.com ARP Learning via ARP Request In FTOS versions prior to 8.3.1.0, FTOS learns via ARP requests only if the target IP specified in the packet matches the IP address of the receiving router interface. This is the case when a host is attempting to resolve the gateway address. If the target IP does not match the incoming interface, the packet is dropped. If there is an existing entry for the requesting host, it is updated (Figure 14-8). Beginning with FTOS version 8.3.1.0, when you enable ARP learning via gratuitous ARP, the system installs a new ARP entry, or updates an existing entry for all received ARP requests (Figure 14-9). Figure 14-8. Learning via Gratuitous ARP not Enabled VLAN ID: 1.1.1.1 ARP Request Target IP: 1.1.1.3 X Host 1 IP: 1.1.1.2 MAC: AA Target IP is not the VLAN interface IP. Update existing Host 1 entry. Drop packet. Host 2 IP: 1.1.1.3 MAC: BB Figure 14-9. Learning via Gratuitous ARP Enabled VLAN ID: 1.1.1.1 ARP Learning via Gratuitous ARP enabled ARP Request Target IP: 1.1.1.3 X Host 1 IP: 1.1.1.2 MAC: AA Target IP is not the VLAN interface IP. Install new entry for Host 1, or update existing Host 1 entry. Drop packet. Host 2 IP: 1.1.1.3 MAC: BB Whether you enable or disable ARP learning via gratuitous ARP, the system does not look up the Target IP. It only updates the ARP entry for the Layer 3 interface with the source IP of the request. Configurable ARP Retries Beginning with FTOS version 8.3.1.0, the number of ARP retries is configurable. 270 | IPv4 Routing