You can configure the types of discovery events the system logs
in your network discovery policy. When you view the discovery events table, the
event type is listed in the
Event column. Descriptions of the discovery event
types follow.
Additional MAC
Detected for Host
This event is generated when the system detects a new MAC
address for a previously discovered host.
This event is often generated when the system detects hosts
passing traffic through a router. While each host has a different IP address,
they all appear to have the MAC address associated with the router. When the
system detects the actual MAC address associated with the IP address, it
displays the MAC address in bold text within the host profile and displays an
“ARP/DHCP detected” message within the event description in the event view.
Client
Timeout
This event is generated when the system drops a client from the
database due to inactivity.
Client
Update
This event is generated when the system detects a payload (that
is, a specific type of content, such as audio, video, or webmail) in HTTP
traffic.
DHCP: IP Address
Changed
This event is generated when the system detects that a host IP
address has changed due to DHCP address assignment.
DHCP: IP Address
Reassigned
This event is generated when a host is reusing an IP address;
that is, when a host obtains an IP address formerly used by another physical
host due to DHCP IP address assignment.
Hops
Change
This event is generated when the system detects a change in the
number of network hops between a host and the device that detects the host.
This may happen if:
-
The device
sees host traffic through different routers and is able to make a better
determination of the host’s location.
-
The device
detects an ARP transmission from the host, indicating that the host is on a
local segment.
Host Deleted:
Host Limit Reached
This event is generated when the host limit on the
Firepower Management Center
is exceeded and a monitored host is deleted from the network map.
Host Dropped:
Host Limit Reached
This event is generated when the host limit on the
Firepower Management Center
is reached and a new host is dropped. Compare this with the previous event
where old hosts are deleted from the network map when the host limit is
reached.
To drop new hosts when the host limit is reached, go to
and set
When Host Limit Reached to
Drop hosts.
Host IOC
Set
This event is generated when an IOC (Indications of Compromise)
is set for a host and generates an alert.
Host
Timeout
This event is generated when a host is dropped from the network
map because the host has not produced traffic within the interval defined in
the network discovery policy. Note that individual host IP addresses and MAC
addresses time out individually; a host does not disappear from the network map
unless all of its associated addresses have timed out.
If you change the networks you want to monitor in your network
discovery policy, you may want to manually delete old hosts from the network
map so that they do not count against your host limit.
Host Type
Changed to Network Device
This event is generated when the system detects that a detected
host is actually a network device.
Identity
Conflict
This event is generated when the system detects a new server or
operating system identity that conflicts with a current active identity for
that server or operating system.
If you want to resolve identity conflicts by rescanning the host
to obtain newer active identity data, you can use Identity Conflict events to
trigger an Nmap remediation.
Identity
Timeout
This event is generated when server or operating system identity
data from an active source times out.
If you want to refresh identity data by rescanning the host to
obtain newer active identity data, you can use Identity Conflict events to
trigger an Nmap remediation.
MAC Information
Change
This event is generated when the system detects a change in the
information associated with a specific MAC address or TTL value.
This event often occurs when the system detects hosts passing
traffic through a router. While each host hnetas a different IP address, they
will all appear to have the MAC address associated with the router. When the
system detects the actual MAC address associated with the IP address, it
displays the MAC address in bold text within the host profile and displays an
“ARP/DHCP detected” message within the event description in the event view. The
TTL may change because the traffic may pass through different routers or if the
system detects the actual MAC address of the host.
NETBIOS Name
Change
This event is generated when the system detects a change to a
host’s NetBIOS name. This event will only be generated for hosts using the
NetBIOS protocol.
New
Client
This event is generated when the system detects a new client.
Note
|
To collect and store client data for analysis, make sure that
you enable application detection in your discovery rules in the network
discovery policy.
|
New
Host
This event is generated when the system detects a new host
running on the network.
This event can also be generated when a device processes NetFlow
data that involves a new host. To generate an event in this case, configure the
network discovery rule that manages NetFlow data to discover hosts.
New Network
Protocol
This event is generated when the system detects that a host is
communicating with a new network protocol (IP, ARP, and so on).
New OS
This event is generated when the system either detects a new
operating system for a host, or a change in a host’s operating system.
New TCP
Port
This event is generated when the system detects a new TCP server
port (for example, a port used by SMTP or web services) active on a host. This
event is not used to identify the application protocol or the server associated
with it; that information is transmitted in the TCP Server Information Update
event.
This event can also be generated when a device processes NetFlow data
involving a server on your monitored networks that does not already exist in
the network map. To generate an event in this case, configure the network
discovery rule that manages NetFlow data to discover applications.
New Transport
Protocol
This event is generated when the system detects that a host is
communicating with a new transport protocol, such as TCP or UDP.
New UDP
Port
This event is generated when the system detects a new UDP server
port running on a host.
This event can also be generated when a device processes NetFlow data
involving a server on your monitored networks that does not already exist in
the network map. To generate an event in this case, configure the network
discovery rule that manages NetFlow data to discover applications.
TCP Port
Closed
This event is generated when the system detects that a TCP port
has closed on a host.
TCP Port
Timeout
This event is generated when the system has not detected
activity from a TCP port within the interval defined in the system’s network
discovery policy.
TCP Server
Information Update
This event is generated when the system detects a change in a
discovered TCP server running on a host.
This event may be generated if a TCP server is upgraded.
UDP Port
Closed
This event is generated when the system detects that a UDP port
has closed on a host.
UDP Port
Timeout
This event is generated when the system has not detected
activity from a UDP port within the interval defined in the network discovery
policy.
UDP Server
Information Update
This event is generated when the system detects a change in a
discovered UDP server running on a host.
This event may be generated if a UDP server is upgraded.
VLAN Tag
Information Update
This event is generated when the system detects a change in the
VLAN tag attributed to a host.