Dell POWERCONNECT 6200 SERIES Configuration Manual

Also see for POWERCONNECT 6200 SERIES: Getting started guide Getting started guide

Contents

56 Switching ConfigurationExample #2: Viewing the DoS Configuration Informationconsole#show dos-controlSIPDIP Mode.................................... EnableFirst Fragment Mode............................ EnableMin TCP Hdr Size............................... 20TCP Fragment Mode.............................. EnableTCP Flag Mode.................................. DisableL4 Port Mode................................... EnableICMP Mode...................................... EnableMax ICMP Pkt Size.............................. 512DHCP SnoopingDynamic Host Configuration Protocol (DHCP) Snooping is a security feature that monitors DHCPmessages between a DHCP client and DHCP server to:• Filter harmful DHCP messages• Build a bindings database of (MAC address, IP address, VLAN ID, port) authorized tuples.DHCP snooping is disabled globally and on all VLANs by default. Ports are untrusted by default.Network administrators can enable DHCP snooping globally and on specific VLANs. They can alsoconfigure ports within the VLAN to be trusted or untrusted. DHCP servers must be reached throughtrusted ports.DHCP snooping enforces the following security rules:• DHCP packets from a DHCP server (DHCPOFFER, DHCPACK, DHCPNAK,DHCPRELEASEQUERY) are dropped if received on an untrusted port.• DHCPRELEASE and DHCPDECLINE messages are dropped if for a MAC addresses in the snoopingdatabase, but the binding's interface is other than the interface where the message was received.• On untrusted interfaces, the switch drops DHCP packets with a source MAC address that does notmatch the client hardware address. This is a configurable option.Dynamic ARP Inspection uses the DHCP snooping bindings database to validate ARP packets.To prevent DHCP packets being used as a DoS attack when DHCP snooping is enabled, the snoopingapplication enforces a rate limit for DHCP packets received on interfaces. DHCP snooping monitors thereceive rate on each interface separately. If the receive rate exceeds a configurable limit, DHCP snoopingbrings down the interface. The user must do “no shutdown” on this interface to further work with thatport. The user can configure both the rate and the burst interval.