full SPF adding An SPF adding as a aftereffect of changes central the aforementioned breadth as a router,
for which the SPF run charge appraise the abounding LSDB.
full amend A acquisition agreement affection by which the acquisition amend includes the absolute set of
routes, alike if some or all of the routes are unchanged.
fully adjoining (OSPF) Any OSPF acquaintance for which the database calamity action has
completed.
Garbage timer See Flush timer.
Gateway Load Balancing Agreement A Cisco-proprietary affection by which assorted routers can
provide interface IP abode redundancy, as able-bodied as account a set of audience to load-balance their
traffic beyond assorted routers central the GLBP group.
gateway of aftermost resort The characters in a Cisco IOS IP acquisition table that identifies the avenue used
by that router as the absence route.
generic acquisition encapsulation A tunneling agreement that can be acclimated to abbreviate many
different agreement types, including IPv4, IPv6, IPsec, and others, to carriage them beyond a
network.
Get In the ambience of SNMP, the Get command is beatific by an SNMP manager, to an agent,
requesting the amount of a distinct MIB capricious articular in the request. The Get appeal identifies
the exact capricious whose amount the administrator wants to retrieve. Introduced in SNMPv1.
GetBulk In the ambience of SNMP, the GetBulk command is beatific by an SNMP manager, to
an agent, requesting the ethics of assorted variables. The GetBulk command allows retrieval
of circuitous structures, like a acquisition table, with a distinct command, as able-bodied as easier MIB
walking.
GetNext In the ambience of SNMP, the GetNext command is beatific by an SNMP manager, to an
agent, requesting the amount of a distinct MIB variable. The GetNext appeal identifies a variable
for which the administrator wants the capricious name and amount of the abutting MIB blade capricious in
sequence.
GLBP See Gateway Load Balancing Protocol.
global acquisition prefix The aboriginal 48 $.25 of an IPv6 all-around address, acclimated for able route
aggregation.
GLOP acclamation 867
GLOP acclamation The ambit 233.0.0.0 through 233.255.255.255 that IANA has aloof (RFC
2770) on an beginning basis. It can be acclimated by anyone who owns a registered autonomous
system cardinal to actualize 256 all-around multicast addresses.
going alive EIGRP abracadabra acceptation that EIGRP has placed a avenue into alive status.
Goodbye (EIGRP) An EIGRP bulletin that is acclimated by a router to acquaint its neighbors back the
router is alluringly shutting down.
graceful restart (OSPF) As authentic in RFC 3623, adroit restart allows for uninterrupted
forwarding in the accident that an OSPF router’s OSPF acquisition action charge restart. The router does
this by aboriginal advice the acquaintance routers that the restart is about to occur; the neighbors charge be
RFC 3623–compliant, and the restart charge action aural the authentic adroitness period.
Graft Ack bulletin Bulletin beatific by a PIM-DM router to a after router back it receives
a Graft bulletin from the after router; beatific application the unicast abode of the downstream
router.
Graft bulletin Bulletin beatific by a PIM-DM router to its upstream router allurement to quickly
restart forwarding the accumulation traffic; beatific application the unicast abode of the upstream router.
granted window See receiver’s advertised window.
GRE See all-encompassing acquisition encapsulation.
half bifold Ethernet affection in which a NIC or Ethernet anchorage can alone address or accept at
the aforementioned burning in time, but not both. Half bifold is appropriate back a achievability of collisions
exists.
hardware chain A baby FIFO chain associated with anniversary router’s concrete interface, for the
purpose of authoritative packets accessible to the interface hardware, removing the charge for a CPU
interrupt to alpha sending the abutting packet out the interface.
HDB3 See High Density Binary 3.
Hello (EIGRP) An EIGRP bulletin that identifies neighbors, exchanges parameters, and is sent
periodically as a keepalive function. Hellos do not crave an Ack.
Hello (OSPF) A blazon of OSPF packet acclimated to ascertain neighbors, analysis for parameter
agreement, and adviser the bloom of addition router.
hello breach With some acquisition protocols, the time aeon amid alternating Hello
messages.
Hello timer An STP timer that dictates the breach at which the Root about-face generates and
sends Accost BPDUs.
High Density Bifold 3 A serial-line encoding accepted like B8ZS, but with anniversary set of four
consecutive 0s actuality afflicted to accommodate a Bipolar Violation to advance synchronization.
Hold timer With EIGRP, the timer acclimated to actuate aback a adjoining router has failed,
based on a router not accepting any EIGRP messages, including Hellos, in this timer period.
Hot Standby Router Agreement A Cisco-proprietary affection by which assorted routers can
provide interface IP abode back-up so that hosts appliance the shared, basic IP abode as their
default aperture can still ability the blow of a arrangement alike if one or added routers fail.
Holddown timer With RIP, a per-route timer (default 180 seconds) that begins aback a route’s
metric changes to a beyond value.
HSRP See Hot Standby Router Protocol.
I/G bit The best cogent bit in the best cogent byte of an Ethernet MAC address, its
value implies that the abode is a unicast MAC abode (binary 0) or not (binary 1).
iBGP See Internal BGP.
IEEE 802.1X An IEEE accepted that, aback acclimated with EAP, provides user affidavit before
their affiliated about-face anchorage allows the accessory to absolutely use the LAN.
IGMP See Internet Accumulation Management Protocol.
IGMP concern A adjustment for optimizing the breeze of multicast IP packets casual through a
LAN switch. The about-face appliance IGMP concern examines IGMP letters to actuate which
ports charge to accept cartage for anniversary multicast group.
IGMPv1 Host Membership Concern A bulletin beatific by the multicast router, by absence every
60 seconds, on anniversary of its LAN interfaces to actuate whether any host wants to accept multicast
traffic for any group.
IGMPv1 Host Membership Report A bulletin that anniversary host sends, either in acknowledgment to a
router Concern bulletin or on its own, to all multicast groups for which it would like to receive
multicast traffic.
IGMPv2 Group-Specific Concern 869
IGMPv2 Group-Specific Concern A bulletin beatific by a router, afterwards accepting a Leave message
from a host, to actuate whether there are still any alive associates of the group. The router uses
the accumulation abode as the destination address.
IGMPv2 Host Membership Concern A bulletin beatific by a multicast router, by absence every
125 seconds, on anniversary of its LAN interfaces to actuate whether any host wants to receive
multicast cartage for any group.
IGMPv2 Host Membership Report A bulletin beatific by anniversary host, either in acknowledgment to a router
Query or on its own, to all multicast groups for which it would like to accept multicast traffic.
IGMPv2 Leave A bulletin beatific by a host aback it wants to leave a group, addressed to the All
Multicast Routers abode 224.0.0.2.
IGMPv3 Host Membership Concern A bulletin beatific by a multicast router, by absence every
125 seconds, on anniversary of its LAN interfaces to actuate whether any host wants to receive
multicast cartage for any group.
IGMPv3 Host Membership Report A bulletin beatific by anniversary host, either in acknowledgment to a router
query or on its own, to all multicast groups for which it would like to accept multicast traffic. The
destination abode on the Report is 224.0.0.22, and a host can specify the antecedent address(es) from
which it would like to accept the accumulation traffic.
InARP See Inverse ARP.
Inform In the ambience of SNMP, the Inform command is beatific by an SNMP administrator to
communicate a set of variables, and their values, to addition SNMP manager. The capital purpose is
to acquiesce assorted managers to barter MIB information, and assignment together, afterwards requiring
each administrator to alone use Get commands to accumulate the data.
infrastructure approach A wireless LAN that includes the use of admission points. Infrastructure
mode connects wireless users to a alive arrangement and allows wireless users to roam throughout a
facility amid altered admission points. All 802.11 abstracts frames in an basement wireless LAN
travel through the admission point.
ingress PE An E-LSR in an MPLS VPN arrangement whose role in a accurate altercation is to
receive unlabeled packets over chump links and again advanced the packets as labeled packets into
the MPLS network.
inner characterization An MPLS appellation apropos to the MPLS characterization aloof afore the IP header. Additionally called
the VPN characterization aback implementing MPLS VPNs.
870 ascribe event
input accident Any accident that could change a router’s EIGRP cartography table, including a
received Update or Query, a bootless interface, or the accident of a neighbor.
Inside All-around abode A NAT appellation anecdotic an IP abode apery a host that resides
inside the action network, with the abode actuality acclimated in packets alfresco the enterprise
network.
Inside Bounded abode A NAT appellation anecdotic an IP abode apery a host that resides
inside the action network, with the abode actuality acclimated in packets central the action network.
inspection aphorism A set of ambit for CBAC to accomplish in its cartage analysis process.
interface ID 64 $.25 at the end of an IPv6 all-around address, acclimated to abnormally analyze anniversary host in
a subnet.
Inter-Switch Articulation Cisco-proprietary VLAN trunking protocol.
internal BGP Refers to how a router angle a BGP associate relationship, in which the associate is in the
same AS.
internal DSCP A appellation acclimated with Cisco LAN switches, apropos to a DSCP amount acclimated when
making QoS decisions about a frame. This amount may not be the absolute DSCP amount in the IP
header encapsulated central the frame.
internal router (OSPF) A router that is not an ABR or ASBR in that all of its interfaces connect
to alone a distinct OSPF area.
Internet Accumulation Management Agreement A advice agreement amid hosts and a
multicast router by which routers apprentice of which multicast groups’ packets charge to be forwarded
onto a LAN.
Invalid timer With RIP, a per-route timer that increases until the router receives a routing
update that confirms the avenue is still valid, aloft which the timer is displace to 0. If the updates cease,
the Invalid timer will grow, until extensive the timer ambience (default 180 seconds), afterwards which the
route is advised invalid.
Inverse ARP Authentic in RFC 1293, this agreement allows a Anatomy Relay–attached accessory to react
to a accustomed LMI “PVC up” bulletin by announcement its Band 3 addresses to the accessory on the
other end of the PVC.
IPCP See IP Control Protocol.
IP forwarding 871
IP Control Agreement The allocation of PPP focused on negotiating IP features—for example, TCP
or RTP attack compression.
IP forwarding The action of forwarding packets through a router. Additionally anxiety IP routing.
IP PBX A basic that interfaces with a buzz appliance IP and provides access to the
Public Switched Telephone Arrangement (PSTN).
IP Precedence A 3-bit acreage in the aboriginal 3 $.25 of the ToS byte in the IP header, acclimated for QoS
marking.
IP prefix account See prefix list.
IP acquisition The action of forwarding packets through a router. Additionally alleged IP forwarding.
IP Antecedent Guard A about-face affection that examines admission frames, comparing the antecedent IP
and MAC addresses to the DHCP concern bounden database, clarification frames whose addresses are
not listed in the database for the admission interface.
IPv4 Adaptation 4 of the IP protocol, which is the about deployed adaptation common (at
publication), and uses 32-bit IP addresses.
IPv6 Adaptation 6 of the IP protocol, which uses 128-bit IP addresses.
ISATAP An IPv6/IPv4 tunneling adjustment that is advised for alteration IPv6 packets within
a armpit breadth a built-in IPv6 infrastructures is not available.
ISL See Inter-Switch Link.
isolated VLAN With clandestine VLANs, a accessory VLAN in which the ports can accelerate and
receive frames alone with abandoned ports in the primary VLAN.
Join/Prune bulletin Beatific by a PIM router to its upstream router to either appeal that the
upstream router advanced the accumulation cartage or stop forwarding the accumulation cartage that is currently
being forwarded. If a PIM router wants to alpha accepting the accumulation traffic, it lists the accumulation address
under the Join field. If it wants the upstream router to stop forwarding the accumulation traffic, it lists the
group abode beneath the Prune field.
joining a accumulation The action of installing a multicast application; additionally referred to as launching
an application.
K amount EIGRP (and IGRP) allows for the use of bandwidth, load, delay, MTU, and link
reliability; the K ethics accredit to an accumulation connected that includes these bristles accessible metric
872 characterization binding
components. Alone bandwidth and adjournment are acclimated by default, to abbreviate recomputation of metrics
for baby changes in accessory metric components.
label bounden In MPLS, the mapping of an IP prefix and a label, which is again advertised to
neighbors appliance LDP.
Label Distribution Agreement The RFC-standard MPLS agreement acclimated to acquaint the binding
(mapping) advice about anniversary accurate IP prefix and associated label. See additionally TDP.
Label Forwarding Advice Base An MPLS abstracts anatomy acclimated for forwarding labeled
packets. The LFIB lists the admission label, which is compared to the admission packet’s label,
along with forwarding instructions for the packet.
Label About-face Router An MPLS appellation apropos to any accessory that can advanced packets that have
MPLS labels.
label switched aisle The aggregate of MPLS labels and links over which a packet will be
forwarded over an MPLS network, from the point of admission to the MPLS arrangement to the point of
egress.
LACP See Articulation Aggregation Control Protocol.
LAPF See Articulation Admission Procedure for Frame-Mode Bearer Services.
Layer 2 burden compression The action of demography the burden central a Band 2 frame,
including the headers of Band 3 and above, burden the data, and again uncompressing the
data on the accepting router.
Layer 2 agreement tunneling Addition name for 802.1Q-in-Q. See 802.1Q-in-Q.
Layer x PDU The PDU acclimated by a accurate band of a networking model, with x defining the
layer.
LCP See Articulation Control Protocol.
LDP See Characterization Distribution Protocol.
Lead Agreeable Agent The agreeable agent in a WCCP cluster, which determines how cartage will
be broadcast aural the cluster.
learning accompaniment An 802.1d STP concise anchorage accompaniment in which the anchorage does not accelerate or receive
frames, but does apprentice the antecedent MAC addresses from admission frames.
LFI 873
LFI See Articulation Fragmentation and Interleaving.
LFIB See Characterization Forwarding Advice Base.
limiting concern ambit (EIGRP) An accomplishment to abate the concern ambit with EIGRP, appliance route
summarization or EIGRP butt routers.
line coding See encoding.
Link Admission Procedure for Frame-Mode Bearer Services An ITU accepted Anatomy Relay
header, including the DLCI, DE, FECN, and BECN $.25 in the LAPF header, and a anatomy check
in the LAPF trailer.
Link Aggregation Control Agreement Authentic in IEEE 802.1AD, defines a messaging protocol
used to accommodate the activating conception of PortChannels (EtherChannels) and to accept which
ports can be placed into an EtherChannel.
Link Control Agreement The allocation of PPP focused on appearance that are altered to any specific
Layer 3 protocol.
Link Fragmentation and Interleaving The action of breaking a anatomy into pieces, sending
some of the fragments, and again sending all or allotment of a altered packet, all of which is done to
reduce the adjournment of the additional packet.
link-local An abode blazon in IPv6 networks that is acclimated alone on the bounded articulation and never beyond
that scope.
Link-State Acknowledgment A blazon of OSPF packet acclimated to accede LSU packets.
link-state advertisement The OSPF abstracts anatomy that describes cartography information.
link-state database The abstracts anatomy acclimated by OSPF to authority LSAs.
link-state acquisition agreement Any acquisition agreement that uses the abstraction of appliance the SPF
algorithm with an LSDB to compute routes.
Link-State Update A blazon of OSPF packet, acclimated to acquaint LSAs to addition router.
listening accompaniment An 802.1d STP concise anchorage accompaniment in which the anchorage does not accelerate or receive
frames, and does not apprentice MAC addresses, but does delay for STP aggregation and for CAM
flushing by the switches in the network.
LLQ See low-latency queuing.
874 LMI
LMI See Bounded Management Interface.
local ciphering An EIGRP router’s acknowledgment to an ascribe event, arch to the use of a feasible
successor or activity alive on a route.
local characterization In MPLS, a appellation acclimated to ascertain a characterization that an LSR allocates and again advertises to
neighboring routers. The characterization is advised “local” on the router that allocates and advertises the
label.
LOCAL_AS A aloof amount for the BGP COMMUNITY aisle aspect that implies that the
route should not be advertised alfresco the bounded amalgamation sub-AS.
Local Management Interface The Anatomy Relay agreement acclimated amid a DCE and DTE to
manage the connection. Signaling letters for SVCs, PVC Status messages, and keepalives are
all LMI messages.
LOCAL_PREF A BGP aisle aspect that is announced throughout a distinct AS to signify
which avenue of assorted accessible routes is the best avenue to be taken aback abrogation that AS. A larger
value is advised to be better.
LOF See Accident of Frame.
Loop Guard Protects adjoin problems acquired by unidirectional links amid two switches.
Watches for accident of accustomed Accost BPDUs, in which case it transitions to a loop-inconsistent state
instead of transitioning to a forwarding state.
loopback chip A affection of Ethernet NICs. Aback the NIC transmits an electrical signal, it
“loops” the transmitted electrical accepted aback assimilate the accept pair. By accomplishing so, if addition NIC
transmits a anatomy at the aforementioned time, the NIC can ascertain the overlapping accustomed electrical signals,
and faculty that a blow has occurred.
LOS Accident of Signal. A T1 anxiety accompaniment that occurs aback the receiver has not accustomed any pulses
of either polarity for a authentic time period.
Loss of Anatomy A T1 anxiety accompaniment that occurs aback the receiver can no best consistently
identify the frame.
low-latency queuing A Cisco IOS queuing apparatus that uses MQC agreement commands,
reserves a minimum bandwidth for some queues, provides acute scheduling for some
queues, and polices those queues to anticipate starvation of lower-priority queues during interface
congestion.
LSA See link-state advertisement.
LSA calamity The action of alternating adjoining routers exchanging LSAs such that all
routers accept an identical LSDB for anniversary breadth to which they are attached.
LSA blazon (OSPF) A analogue that determines the abstracts anatomy and advice adumbrated by a
particular LSA.
LSAck See Link-State Acknowledgment.
LSDB See link-state database.
LSP See characterization switched path.
LSP articulation A distinct characterization and articulation that is allotment of a complete LDP. See additionally characterization switched
path.
LSR See Characterization About-face Router.
LSRefresh Link-State Refresh. A timer that determines how generally the basic router should
reflood an LSA, alike if no changes accept occurred to the LSA.
LSU See Link-State Update.
LxPDU See Band x PDU.
LZS The Lempel Ziv STAC compression algorithm is acclimated in Anatomy Relay networks to define
dynamic concordance entries that account a bifold cord from the aeroembolism abstracts and an associated
smaller cord that represents it during transmission—thereby abbreviation the cardinal of $.25 acclimated to
send data.