224.0.0.2 The IP abode to which Label Administration Agreement (LDP) sends LDP Hellos. Also
used in IP multicast to accelerate packets to all multicast routers.
224.0.0.5 The All OSPF Routers multicast IP address, listened for by all OSPF routers.
224.0.0.6 The All OSPF DR Routers multicast IP address, listened for by DR and BDR
routers.
2Way (OSPF) A acquaintance accompaniment that signifies the added router has accomplished acquaintance status,
having anesthetized the constant check.
6to4 An IPv6/IPv4 tunneling adjustment that allows abandoned IPv6 domains to be affiliated over
an IPv4 network.
802.11a A wireless LAN concrete bandage that operates at up to 54-Mbps abstracts ante using
OFDM in the 5-GHz band.
802.11b A wireless LAN concrete bandage that operates at up to 11-Mbps abstracts ante application DSSS
in the 2.4-GHz band.
802.11g A wireless LAN concrete bandage that is astern accordant with 802.11b and
operates at up to 54-Mbps abstracts ante application OFDM in the 2.4-GHz band.
802.11n A prestandard (at the time of publication) wireless LAN concrete bandage that offers
data ante in the hundreds of megabits per second.
802.1Q The IEEE connected agreement for VLAN trunking.
802.1Q-in-Q A apparatus in which VLAN advice can extend over addition set of
802.1Q trunks by tunneling the aboriginal 802.1Q cartage with addition 802.1Q tag. It allows a
service provider to abutment cellophane VLAN casework with assorted customers, alike if the
customers use overlapping VLAN numbers.
846 AAA
AAA See Authentication, authorization, and accounting.
AAAA In IPv6 DNS, the IPv6 agnate of an IPv4 DNS A record.
ABR See Breadth Border Router.
Access Control Entry An alone band in an ACL.
Access Control Server A appellation apropos generically to a server that performs abounding AAA
functions. It additionally refers to the software artefact Cisco Secure Admission Control Server.
access articulation In Anatomy Relay, a articulation amid a router and a Anatomy Relay switch.
access amount The acceleration at which the admission articulation is clocked. This best affects the amount of the
connection and abounding aspects of cartage abstraction and policing, compression, affection of service, and
other agreement options.
ACE See Admission Control Entry.
Ack (EIGRP) An EIGRP bulletin that is acclimated to accede reliable EIGRP messages,
namely Update, Query, and Reply messages. Acks do not crave an Ack.
ACS See Admission Control Server.
active (EIGRP) A accompaniment for a avenue in an EIGRP cartography table that indicates that the router is
actively sending Query letters for this route, attempting to validate and apprentice the accepted best
route to that subnet.
active approach FTP Defines a accurate behavior for FTP apropos the enactment of data
TCP connections. In alive mode, the FTP applicant uses the FTP PORT command, over the FTP
control connection, to acquaint the FTP server the anchorage on which the applicant should be alert for a new
data connection. The server uses acclaimed anchorage 20, and initiates a TCP affiliation to the FTP
client’s earlier-declared port.
active scanning Anniversary 802.11 base periodically sends a delving appeal anatomy on anniversary RF
channel and monitors delving acknowledgment frames that all admission credibility aural ambit accelerate back. Stations
use the arresting courage of the delving acknowledgment frames to actuate which admission point or ad hoc
network to accessory with.
actual chain abyss The absolute cardinal of packets in a chain at a accurate time.
ad hoc approach A wireless LAN that alone includes wireless users and no admission points. 802.11
data frames in an ad hoc arrangement biking anon amid wireless users.
adaptive abstraction 847
adaptive abstraction A Anatomy Relay cartage abstraction affection during which the abstraction amount is
reduced back the shaper notices bottleneck through the cancellation of BECN or ForeSight messages.
Address Resolution Agreement Defined in RFC 826, a agreement acclimated on LANs so that an IP host
can ascertain the MAC abode of addition accessory that is application a accurate IP address.
adjacency (EIGRP) Often acclimated synonymously with neighbor, but with accent on the fact
that all appropriate ambit match, acceptance acquisition updates to be exchanged amid the routers.
adjacency table A table acclimated by CEF that holds advice about adjoining IP hosts to which
packets can be forwarded.
adjacent (OSPF) Any OSPF acquaintance for which the database calamity action has completed.
adjacent-layer alternation On a distinct computer, one bandage provides a account to a college layer.
The software or accouterments that accouterments the college bandage requests that the abutting lower layer
perform the bare function.
administrative scoping Controls the administration of multicast cartage for the clandestine multicast
address ambit 239.0.0.0 to 239.255.255.255 by configuring a clarify and applying it on the
interfaces.
administrative weight A Cisco-proprietary BGP feature. The authoritative weight can be
assigned to anniversary NLRI and aisle locally on a router, impacting the bounded router’s best of the best
BGP routes. The amount cannot be announced to addition router.
administratively scoped addresses The ambit 239.0.0.0 through 239.255.255.255 that IANA
has assigned for use in clandestine multicast domains.
Advanced Encryption Accepted A above encryption apparatus that is allotment of the 802.11i
standard and has abundant stronger aegis than TKIP.
advertised window See receiver’s advertised window.
AES See Advanced Encryption Standard.
AF See Assured Forwarding.
aggregatable all-around unicast abode An IPv6 abode architecture acclimated for about registered IPv6
addresses.
aggregate avenue Addition appellation for arbitrary route.
848 AGGREGATOR
AGGREGATOR An another transitive BGP aisle aspect that, for a arbitrary route, lists the
BGP RID and ASN of the router that created the summary.
AIS Alarm Indication Signal. With T1s, the convenance of sending all bifold 1s on the band in
reaction to problems, to accommodate arresting transitions and acquiesce accretion of synchronization and
framing.
All OSPF DR Routers The multicast IP abode 224.0.0.6, listened for by DR and BDR
routers.
All OSPF Routers The multicast IP abode 224.0.0.5, listened for by all OSPF routers.
Alternate Mark Inversion A serial-line encoding accepted that sends alternating absolute and
negative 3-volt signals for bifold 1, and no arresting (0 V) for bifold 0.
alternate approach One of the two modes of MDRR, in which the antecedence chain is serviced
between anniversary application of the non-priority queues.
Alternate accompaniment An 802.1w RSTP anchorage accompaniment in which the anchorage is not the Basis Anchorage but is available
to become the basis anchorage if the accepted basis anchorage goes down.
AMI See Alternate Mark Inversion.
anycast An IPv6 abode blazon that is acclimated by a cardinal of hosts in a arrangement that are providing
the aforementioned service. Hosts accessing the account are baffled to the abutting host in an anycast
environment based on acquisition agreement metrics.
AR See admission rate.
area (OSPF) A abutting accumulation of abstracts links that allotment the aforementioned OSPF breadth number.
Area Border Router An OSPF router that connects to the courage breadth and to one or more
non-backbone area.
ARP See Abode Resolution Protocol.
AS cardinal A cardinal amid 1 and 64,511 (public) and 64,512 and 65,535 (private) assigned
to an AS for the purpose of anecdotic a specific BGP domain.
AS_CONFED_SEQ A blazon of AS_PATH articulation consisting of an ordered account of
confederation sub-ASNs through which a avenue has been advertised.
AS_CONFED_SET 849
AS_CONFED_SET A blazon of AS_PATH articulation consisting of an unordered account of
confederation sub-ASNs circumscribed from basic subnets of a arbitrary BGP avenue created
inside a confederation.
AS_PATH A BGP aisle aspect that lists ASNs through which the avenue has been advertised.
The AS_PATH includes four types of segments: AS_SEQ, AS_SET, AS_CONFED_SEQ, and
AS_CONFED_SET. Often, this appellation is acclimated synonymously with AS_SEQ.
AS_PATH admission account A Cisco IOS agreement tool, application the ip as-path access-list
command, that defines a account of statements that bout the AS_PATH BGP aisle aspect using
regular expressions.
AS_PATH breadth A adding of the breadth of the AS_PATH PA, which includes 1 for each
number in the AS_SEQ, 1 for an absolute AS_SET segment, and possibly added considerations.
AS_PATH prepending This appellation has two BGP-related definitions. First, it is the normal
process in which a router, afore sending an Amend to an eBGP peer, adds its bounded ASN to the
beginning of the AS_PATH aisle attribute. Second, it is the acquisition action of agilely adding
one or added ASNs to the alpha of a route’s AS_PATH aisle attribute, about to amplify the
AS_PATH and accomplish the avenue beneath adorable in the BGP accommodation process.
AS_SEQUENCE A blazon of AS_PATH articulation consisting of an ordered account of ASNs through
which the avenue has been advertised.
AS_SET A blazon of AS_PATH articulation consisting of an unordered account of ASNs consolidated
from basic subnets of a arbitrary BGP route.
ASBR Free Arrangement Boundary Router. An OSPF router that redistributes routes from
some added antecedent into OSPF.
ASN See AS number.
Assert bulletin Sent by a PIM-DM or PIM-SM router back it receives a multicast packet for a
group on a LAN interface that is in the approachable interface account for the group; includes the
administrative ambit of the unicast acquisition agreement acclimated to apprentice the arrangement of the antecedent with
its metric value.
association ID Back a wireless base connects to an admission point, the admission point assigns
an affiliation ID (AID) to the station. Various protocols, such as power-save mode, accomplish use of
the affiliation ID.
Assured Forwarding A set of DiffServ PHBs that defines 12 DSCP values, with four queuing
classes and three bead probabilities aural anniversary queuing class.
850 ATOMIC_AGGREGATE
ATOMIC_AGGREGATE A acclaimed arbitrary BGP aisle aspect that flags a avenue as
being a arbitrary route.
authentication With acquisition protocols, the action by which the router accepting a routing
update determines if the acquisition amend came from a trusted router.
authentication, authorization, and accounting Three amount aegis functions.
authentication adjustment A appellation apropos generically to means in which a router or about-face can
determine whether a accurate accessory or user should be accustomed access.
authentication server In 802.1X, the computer that food usernames/passwords and verifies
that the absolute ethics were submitted afore acceptance the user.
authenticator The 802.1X action implemented by a switch, in which the about-face translates
between EAPoL and RADIUS letters in both directions, and enables/disables ports based on
the success/failure of authentication.
auto-negotiation Ethernet action by which accessories absorbed to the aforementioned cable accommodate their
speed and the bifold settings over the cable.
autonomous arrangement In BGP, a set of routers central a distinct authoritative authority, grouped
together for the purpose of authoritative acquisition behavior for the routes advertised by that accumulation to
the Internet.
Auto-RP Auto-Rendezvous Point. Cisco-proprietary agreement that can be acclimated to baptize an
RP and accelerate RP-Announce letters that acquaint its IP abode and groups. Also, it can be used
to baptize a mapping abettor that interprets what IP abode RP is announcement and for what groups.
A mapping abettor sends this advice in the RP-Discovery letters so that all PIM-SM routers
can apprentice the IP abode of the RP and groups it is acknowledging automatically.
average chain abyss Calculated altitude based on the absolute chain abyss and the
previous average. Advised to acquiesce WRED to acclimatize boring to accelerated changes of the absolute queue
depth.
B8ZS See Bipolar 8 Zero Substitution.
backbone breadth (OSPF) Breadth 0; the breadth to which all added OSPF areas abundant affix in order
for OSPF to work.
BackboneFast Cisco-proprietary STP affection in which switches use messaging to affirm the
loss of Hello BPDUs in a switch’s Basis Port, to abstain accepting to delay for maxage to expire,
resulting in faster convergence.
backup accompaniment 851
backup appointed router In OSPF, a router that is able to booty over the appointed router.
backup accompaniment An 802.1w RSTP anchorage accompaniment in which the anchorage is an another Appointed Anchorage on
some LAN segment.
Backward Explicit Bottleneck Notification A bit central the Anatomy Relay attack that, when
set, implies that bottleneck occurred in the administration adverse (or backward) as compared with the
direction of the frame.
Bc See Committed Burst.
Bc brazier Jargon acclimated to accredit to the aboriginal of two buckets in the bifold badge brazier model; its
size is Bc.
BDR See advancement appointed router.
Be See Excess Burst.
Be brazier Jargon acclimated to accredit to the additional of two buckets in the bifold badge brazier model; its
size is Be.
beacon An 802.11 anatomy that admission credibility or stations in ad hoc networks accelerate periodically so
that wireless stations can ascertain the attendance of a wireless LAN and alike use of certain
protocols, such as power-save mode.
BECN See Astern Explicit Bottleneck Notification.
BGP See Border Aperture Protocol.
BGP accommodation action A set of rules by which BGP examines the capacity of assorted BGP
routes for the aforementioned NLRI and chooses the distinct best BGP avenue to install in the bounded BGP table.
BGP table A table central a router that holds the aisle attributes and NLRI accepted by the BGP
implementation on that router.
BGP Amend A BGP bulletin that includes aloof routes, aisle attributes, and NLRI.
Bipolar 8 Zero Substitution A serial-line encoding accepted that substitutes Bipolar Violations
in a cord of eight bifold 0s to accommodate abundant arresting transitions to advance synchronization.
Bipolar Violation For some encoding schemes, after signals charge use adverse polarity
in an accomplishment to abate DC current. A BPV occurs back after signals are of the aforementioned polarity.
852 blocking state
blocking accompaniment An 802.1d STP anchorage accompaniment in which the anchorage does not accelerate or accept frames,
except for alert for accustomed Hello BPDUs.
boot acreage The low-order 4 $.25 of the agreement register. These $.25 absolute a router to load
either ROMMON software (boot acreage 0x0), RXBOOT software (boot acreage 0x1), or a full-function
IOS image.
Boot Agreement A accepted (RFC 951) agreement by which a LAN-attached host can dynamically
broadcast a appeal for a server to accredit it an IP address, forth with added agreement settings,
including a subnet affectation and absence aperture IP address.
BOOTP See Cossack Protocol.
bootstrap router In multicast (IPv4 and IPv6), the action that assembly multicast groups with
rendezvous credibility (RPs) in PIM BSR mode.
Border Aperture Agreement An exoteric acquisition agreement advised to barter prefix information
between altered free systems. The advice includes a affluent set of characteristics
called aisle attributes, which in about-face allows for abundant adaptability apropos acquisition choices.
BPDU Guard Cisco-proprietary STP affection in which a about-face anchorage monitors for STP BPDUs
of any kind, err-disabling the anchorage aloft cancellation of any BPDU.
BPV See Bipolar Violation.
broadcast abode Ethernet MAC abode that represents all accessories on the LAN.
broadcast breadth A set of all accessories that accept advertisement frames basic from any
device aural the set. Accessories in the aforementioned VLAN are in the aforementioned advertisement domain.
broadcast subnet Back subnetting a chic A, B, or C address, the subnet for which all subnet
bits are bifold 1.
BSR See bootstrap router.
CB Marking See Class-Based Marking.
CBAC See Context-Based Admission Control.