Table of Contents
Advertisement
Allow Zero IP
Forward DHCP PKT
Mode
Stop Learning
Threshold (0-500)
Recover Learning
Max Entry (1-50)
IMP Entry Settings
The table on this window, which is also known as the "IMPB white list," is used to create Static IP-MAC-Port Binding entries on
the Switch. .
To view this window, click Security > IP-MAC-Port Binding > IMP Entry Settings, as shown below:
®
xStack
DGS-3426G Layer 2 Gigabit Ethernet Managed Switch
setting.
Enabled Loose – This mode provides a looser way of control. If the user selects loose mode,
the Switch will forward all packets by default. However, it will still inspect incoming ARP
packets and compare them with the Switch's IMPB white list entries. If the IP-MAC pair of a
packet is not found in the white list, the Switch will block the MAC address. A major benefit of
Loose state is that it uses less CPU resources because the Switch only checks incoming ARP
packets. However, it also means that Loose state cannot block users who send only unicast IP
packets. An example of this is that a malicious user can perform DoS attacks by statically
configuring the ARP table on their PC. In this case, the Switch cannot block such attacks
because the PC will not send out ARP packets.
Use the drop-down menu to enable or disable this feature. Once enabled, the Switch will allow
ARP packets with a Source IP of 0.0.0.0 to pass through.
This is useful in some scenarios when a client (for example, a wireless Access Point,) sends
out an ARP request packet before accepting the IP address from a DHCP server. In this case,
the ARP request packet sent out from the client will contain a Source IP of 0.0.0.0. The Switch
will need to allow such packets to pass, or else the client cannot know if there is another
duplicate IP address in the network.
By default, the Switch will forward all DHCP packets. However, if the port state is set to Strict,
all DHCP packets will be dropped. In that case, select Enable so that the port will forward
DHCP packets even under Strict state. Enabling this feature also ensures that DHCP snooping
works properly.
Use the drop-down menu to select ARP or ACL mode.
ARP Mode – When selecting this mode, the Switch will perform ARP Packet Inspection only
and no ACL rules will be used.
ACL Mode – When selecting this mode, the Switch will perform IP Packet Inspection in
addition to ARP Packet Inspection. ACL rules will be used under this mode.
Whenever a MAC address is blocked by the Switch, it will be recorded in the Switch's L2
Forwarding Database (FDB) and associated with a particular port. To prevent the Switch FDB
from overloading in case of an ARP DoS attack, the administrator can configure the threshold
when a port should stop learning illegal MAC addresses.
Enter a Stop Learning threshold between 0 and 500. Entering 500 means the port will enter the
Stop Learning state after 500 illegal MAC entries and will not allow additional MAC entries,
both legal or illegal, to be learned on this port. In the Stop Learning state, the port will also
automatically purge all blocked MAC entries on this port. Traffic from legal MAC entries are still
forwarded.
Entering 0 means no limit has been set and the port will keep learning illegal MAC addresses.
This feature can only be applied when a port is already in Stop Learning state. Check Normal
to recover the port back to normal state, under which the port will start learning both illegal and
legal MAC addresses again.
Selecting this feature when the port is in Normal state will do nothing.
Specifies the maximum number of dynamic (DHCP snooped) IP-MAC-Port Binding entries that
can be learned on the port. Enter a value between 1 to 50 to restrict dynamic IMPB entries on
this port.
By default, the-per port max entry has No Limit.
229
Advertisement
Table of Contents
