Glossary
GL-24
Cisco Router and Security Device Manager 2.5 User’s Guide
OL-4015-12
NetFlow A feature of some routers that allows them to categorize incoming packets into
flows. Because packets in a flow often can be treated in the same way, this
classification can be used to bypass some of the work of the router and accelerate
its switching operation.
network A network is a group of computing devices which share part of an IP address
space and not a single host. A network consists of multiple “nodes” or devices
with IP address, any of which may be referred to as hosts. See also Internet,
Intranet, IP, LAN.
network bits In a subnet mask, the number of bits set to binary 1. A subnet mask of
255.255.255.0 has 24 network bits, because 24 bits in the mask are set to 1. A
subnet mask of 255.255.248 has 17 network bits.
network module A network interface card that is installed in the router chassis to add
functionality to the router. Examples are Ethernet network modules, and IDS
network modules.
NHRP Next Hop Resolution protocol. A client and server protocol used in DMVPN
networks, in which the hub router is the server and the spokes are t he clients. The
hub maintains an NHRP database of the public interface addresses of the each
spoke. Each spoke registers its real address when it boots and queries the NHRP
database for real addresses of the destination spokes in order to build direct
tunnels to them.
non-repudiation
service
A third-party security service that stores evidence for later, possible retrieval,
regarding the origin and destination of all data included i n a communication —
without storing the actual data. This evidence can be used to safeguard all
participants in that communication against false denials by any participant of
having sent information, as well as false denials by any participan t of having
received information.
NTP Network Time Protocol. A protocol to synchronize the system clocks on network
devices. NTP is a UDP protocol.
NVRAM Non-volatile random access memory.