Netgear XCM8806 Chassis User Manual - Page 437
Limiting Dynamic MAC Addresses, Configuring Limit Learning
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NETGEAR 8800 User Manual • Limit the number of dynamically-learned MAC addresses allowed per virtual port. For more information, see Limiting Dynamic MAC Addresses on page 437. • "Lock" the FDB entries for a virtual port, so that the current entries will not change, and no additional addresses can be learned on the port. For information, see MAC Address Lockdown on page 439. Note: You can either limit dynamic MAC FDB entries or lockdown the current MAC FDB entries, but not both. • Set a timer on the learned addresses that limits the length of time the learned addresses will be maintained if the devices are disconnected or become inactive. For more information, see MAC Address Lockdown with Timeout on page 440. • Use ACLS to prioritize or stop packet flows based on the source MAC address of the ingress virtual LAN (VLAN) or the destination MAC address of the egress VLAN. For more information about ACL policies, see ACLs on page 299. • Enhance security, depending on your network configuration, by disabling Layer 2 flooding. For more information about enabling and disabling Layer 2 flooding, see the section Managing Egress Flooding on page 281. Limiting Dynamic MAC Addresses You can set a predefined limit on the number of dynamic MAC addresses that can participate in the network. After the FDB reaches the MAC limit, all new source MAC addresses are blackholed at both the ingress and egress points. These dynamic blackhole entries prevent the MAC addresses from learning and responding to Internet Control Message Protocol (ICMP) and address resolution protocol (ARP) packets. Note: Blackhole FDB entries added due to MAC security violations on NETGEAR 8800 switches are removed after each FDB aging period regardless of whether the MAC addresses in question are still sending traffic. If the MAC addresses are still sending traffic, the blackhole entries will be re-added after they have been deleted. Configuring Limit Learning To limit the number of dynamic MAC addresses that can participate in the network, use the limit-learning option in following command: configure ports vlan [limit-learning {action [blackhole | stop-learning]} | lock-learning | unlimited-learning | unlock-learning] This command specifies the number of dynamically-learned MAC entries allowed for these ports in this VLAN. The range is 0 to 500,000 addresses. Chapter 17. Security | 437
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