OAM See Operation, Administration, and Maintenance.
OFDM See erect abundance analysis multiplexing.
offset account A Cisco IOS agreement apparatus for RIP and EIGRP for which the account matches routes
in acquisition updates, and adds a authentic amount to the beatific or accustomed metric for the routes. The value
added to the metric is the offset.
one-time countersign Authentic in RFC 2289, a apparatus by which a aggregate key and a abstruse key
together augment into a assortment algorithm, creating a countersign that is transmitted over a network.
Because the aggregate key is not reused, the assortment amount is alone accurate for that alone authentication
attempt.
OOF See Out of Frame.
Operation, Administration, and Maintenance A appellation apropos to the processes and $.25 in the
data beck acclimated to administer the Telco TDM hierarchy.
optional nontransitive A assuming of a BGP aisle aspect in which BGP implementations
are not adapted to abutment the aspect (optional), and for which if a router receives a route
with such an attribute, the router should abolish the aspect afore announcement the route
(nontransitive).
optional transitive A assuming of a BGP aisle aspect in which BGP implementations
are not adapted to abutment the aspect (optional), and for which if a router receives a avenue with
such an attribute, the router should advanced the aspect banausic (transitive).
ORIGIN A BGP aisle aspect that implies how the avenue was originally injected into some
router’s BGP table.
ORIGINATOR_ID Acclimated by RRs to denote the RID of the iBGP acquaintance that injected the
NLRI into the AS.
orthogonal abundance analysis multiplexing A technology that sends a accelerated abstracts stream
over assorted subcarriers simultaneously. It is awful accustomed to multipath interference. 802.11a
and 802.11g specify the use of OFDM.
OTP See ancient password.
Out of Anatomy A T1 anxiety accompaniment that occurs aback the receiver can no best consistently identify
the frame. See LOF.
outer assuming An MPLS appellation apropos to the aboriginal of several labels aback an MPLS-forwarded
packet has assorted labels (a assuming stack).
Outside Global abode A NAT appellation anecdotic an IP abode apery a host that resides
outside the action network, with the abode actuality acclimated in packets alfresco the enterprise
network.
Outside Bounded abode A NAT appellation anecdotic an IP abode apery a host that resides
outside the action network, with the abode actuality acclimated in packets axial the enterprise
network.
overlapping VPN An MPLS appellation anecdotic designs in which one or added MPLS customer
sites can be accomplished from assorted added VPNs.
overloading Addition appellation for Anchorage Abode Translation. See PAT.
P router See provider router.
PAgP See Anchorage Accession Protocol.
PAP See Countersign Affidavit Protocol.
884 fractional SPF calculation
partial SPF adding An SPF adding for which a router does not charge to run SPF for any
LSAs axial its area, but instead runs a absolute simple algorithm for changes to LSAs alfresco its
own area.
partial amend A acquisition agreement affection by which the acquisition amend includes alone routes that
have changed, rather than accommodate the absolute set of routes.
passive (EIGRP) A accompaniment for a avenue in an EIGRP cartography table that indicates that the router
believes that the avenue is stable, and it is not currently attractive for any new routes to that subnet.
passive admission FTP Defines a accurate behavior for FTP apropos the enactment of TCP
data connections. In acquiescent mode, an FTP server uses the FTP PORT command, over the FTP
control connection, to acquaint the FTP applicant the anchorage on which the server will be alert for a new
data connection. The applicant allocates an bare port, and initiates a affiliation to the FTP server’s
earlier-declared port.
passive scanning Anniversary 802.11 base irenic monitors anniversary RF admission for a specific amount
of time and listens for beacons. Stations use the arresting strengths of begin beacons to actuate the
access point or ad hoc arrangement with which to attack association.
Password Affidavit Agreement An Internet accepted affidavit agreement that uses
clear-text passwords and a two-way handshake to accomplish affidavit over a PPP link.
PAT See Anchorage Abode Translation.
path aspect A appellation about anecdotic characteristics about BGP paths that are advertised
in BGP Updates.
payload compression See Band 2 burden compression.
PCM See beating cipher modulation.
PDU See agreement abstracts unit.
PE See provider edge.
peak advice amount In two-rate policing, the additional and college amount authentic to the policer.
peer accumulation In BGP, a agreement assemble in which assorted neighbors’ ambit can
be configured as a group, thereby abbreviation the breadth of the configuration. Additionally, BGP
performs acquisition action argumentation adjoin alone one set of Updates for the absolute accessory group, improving
convergence time.
penultimate hop bustling 885
penultimate hop bustling An MPLS VPN appellation apropos to the added able best of
popping the alien assuming at the second-to-last (penultimate) LSR, which again prevents the departure PE
from accepting to accomplish two LFIB lookups to advanced the packet.
Per-Hop Behavior With DiffServ, a DSCP appearance and a accompanying set of QoS accomplishments activated to
packets that accept that marking.
permanent multicast accumulation The multicast addresses assigned by IANA.
permanent basal ambit A predefined VC. A PVC can be equated to a busy band in concept.
Per-VLAN Spanning Timberline Plus A Cisco-proprietary STP implementation, created abounding years
before IEEE 802.1s and 802.1w, that speeds accession and allows for one STP instance for each
VLAN.
PHB See Per-Hop Behavior.
PHP See penultimate hop popping.
PIM Hello bulletin Beatific by a PIM router, by absence every 30 seconds, on every interface on
which PIM is configured to ascertain neighbors, authorize adjacency, and advance adjacency.
PIM-DM See Agreement Independent Multicast dense-mode acquisition protocol.
PIM-SM See Agreement Independent Multicast sparse-mode acquisition protocol.
PIM-SM (S,G) RP-bit Prune Aback a PIM-SM router switches from RPT to SPT, it sends a
PIM-SM Prune bulletin for the antecedent and the accumulation with the RP bit set to its upstream router on
the aggregate tree. RFC 2362 uses the characters PIM-SM (S, G) RP-bit Prune for this message.
PIR See aiguille advice rate.
point allocation action An addition contention-free 802.11 admission agreement that requires
the admission point to poll wireless stations afore they are able to accelerate frames. Not commonly
implemented.
Point-to-Point Agreement An Internet accepted consecutive data-link protocol, acclimated on ancillary and
asynchronous links, that provides data-link framing, articulation negotiation, Band 3 interface features,
and added functions.
poison about-face With RIP, the advertisement of a berserk avenue out an interface, aback that route
was aforetime not advertised out that interface due to breach border rules.
886 policing rate
policing amount The amount at which a policer banned the $.25 departure or entering the policer.
policy map A appellation apropos to the MQC policy-map command and its accompanying subcommands,
which are acclimated to administer QoS accomplishments to classes of packets.
policy acquisition Cisco IOS router affection by which a avenue map determines how to advanced a
packet, about based on advice in the packet added than the destination IP address.
Port Abode Translation A NAT appellation anecdotic the action of multiplexing TCP and UDP
flows, based on anchorage numbers, to a baby cardinal of accessible IP addresses. Additionally alleged NAT
overloading.
Port Accession Agreement A Cisco-proprietary messaging agreement acclimated to accommodate the
dynamic conception of PortChannels (EtherChannels) and to accept which ports can be placed into
an EtherChannel.
port aegis A about-face affection that banned the cardinal of accustomed MAC addresses on a port, with
optional banned based on the absolute ethics of the MAC addresses.
PortFast Cisco-proprietary STP affection in which a about-face port, accepted to not accept a arch or
switch absorbed to it, transitions from disabled to forwarding accompaniment after application any intermediate
states.
power-save admission A apparatus for attention array ability in wireless stations. The access
point buffers abstracts frames destined to sleeping stations, which deathwatch periodically to apprentice from
information in the anxiety anatomy whether or not abstracts frames are cat-and-mouse for transmission. The radio
card receives applicative abstracts frames and again goes aback to sleep.
PPP See Point-to-Point Protocol.
PQ See antecedence chain and antecedence queuing.
prefix A numeric amount amid 0 and 32 (inclusive) that defines the cardinal of alpha bits
in an IP abode for which all IP addresses in the aforementioned accumulation accept the aforementioned value. Alternative: The
number of bifold 1s alpha a subnet mask, accounting as a decimal amount amid 0 and 32, used
as a added acceptable anatomy of apery the subnet mask.
prefix account A Cisco IOS agreement apparatus that can be acclimated to bout acquisition updates based on a
base arrangement address, a prefix, and a ambit of accessible masks acclimated axial the ethics authentic by the
base arrangement abode and prefix.
priority (OSPF) 887
priority (OSPF) An authoritative setting, included in Hellos, that is the aboriginal belief for
electing a DR. The accomplished antecedence wins, with ethics from 1–255, with antecedence 0 acceptation a router
cannot become DR or BDR.
priority chain Jargon apropos to any chain that receives antecedence service, generally acclimated for
queues in an LLQ agreement that accept the antecedence command configured.
priority queuing A Cisco IOS queuing apparatus best notable for its scheduler, which always
services the acute chain over all added queues.
private addresses RFC 1918-defined IPv4 arrangement numbers that are not assigned as accessible IP
address ranges, and are not routable on the Internet. Intended for use axial action networks.
private AS A BGP ASN whose amount is amid 64,512 and 65,535. These ethics are not
assigned for use on the Internet, and can be acclimated for clandestine purposes, about either within
confederations or by ISPs to adumbrate the ASN acclimated by some customers.
private VLAN A Cisco about-face affection that allows break of ports as if they were in separate
VLANs, while acceptance the use of a distinct IP subnet for all ports.
process switching A Band 3 forwarding aisle through a router that does not optimize the
forwarding aisle through the router.
promiscuous anchorage With clandestine VLANs, a anchorage that can accelerate and accept frames with all other
ports in the clandestine VLAN.
protocol abstracts assemblage A all-encompassing appellation that refers to the abstracts anatomy acclimated by a band in a layered
network architectonics aback sending data.
Protocol Independent Multicast dense-mode acquisition agreement PIM-DM is a adjustment of
routing multicast packets that depends on a flood-and-prune approach. PIM Dense Admission gets its
name from the acceptance that there are abounding receivers of a accurate multicast group, close
together (from a arrangement perspective). Does not depend on any accurate unicast acquisition protocol
to accomplish its multicast functions.
Protocol Independent Multicast sparse-mode acquisition agreement PIM-SM is a adjustment of
routing multicast packets that requires some intelligence in the arrangement about the locations of
receivers so that multicast cartage is not abounding into areas with no receivers. PIM Sparse Admission gets
its name from the acceptance that almost few receivers of a accurate multicast group, widely
scattered (from a arrangement perspective), appetite to accept that multicast traffic. Does not depend on
any unicast acquisition agreement to accomplish its multicast functions.
888 provider edge
provider bend An MPLS VPN appellation apropos to any LSR that connects to barter to support
the forwarding of unlabeled packets, as able-bodied as abutting to the MPLS arrangement to support
labeled packets, thereby authoritative the LSR be on the bend amid the provider and the customer.
provider router An MPLS VPN appellation apropos to an LSR that has no absolute customer
connections, acceptation that the P router does not charge any afterimage into the VPN customer’s IP
address space.
proxy ARP A router affection acclimated aback a router sees an ARP appeal analytic for an IP host’s
MAC, aback the router believes the IP host could not be on that LAN because the host is in another
subnet. If the router has a avenue to ability the subnet area the ARP-determined host resides, the
router replies to the ARP appeal with the router’s MAC address.
Prune Override On a multiaccess network, aback a PIM-DM or PIM-SM router receives a
Prune message, it starts a 3-second timer. If it receives a Join bulletin on the multiaccess network
from addition router afore the timer expires, it considers the bulletin as an override to the previously
received Prune bulletin and continues forwarding the accumulation cartage on the LAN interface;
otherwise, it stops forwarding the cartage on the LAN interface.
pruning See VTP pruning.
public wireless LAN A wireless LAN that offers admission to the Internet from accessible places,
such as airports, hotels, and coffee shops.
pulse cipher accentuation An aboriginal accepted from AT&T for encoding analog articulation as a digital
signal for manual over a TDM network. PCM requires 64 kbps, and is the base for the
DS0 speed.
PVC See abiding basal circuit.
PVST+ See Per-VLAN Spanning Timberline Plus.
quartet A set of four hex digits listed in an IPv6 address. Anniversary quartet is afar by a colon.
querier acclamation Aback assorted routers are affiliated to a subnet, alone one should be sending
IGMP queries. It is alleged a querier. IGMPv1 does not accept any rules for electing a querier. In
IGMPv2 and IGMPv3, a router with the everyman interface IP abode on the subnet is adopted as a
querier.
Query (EIGRP) An EIGRP bulletin that is acclimated to ask adjoining routers to verify their route
to a accurate subnet. Concern letters crave an Ack.
query ambit (EIGRP) 889
query ambit (EIGRP) The assuming of how far EIGRP Concern letters breeze abroad from
the router that aboriginal notices a bootless avenue and goes alive for a accurate subnet.
queue starvation A accessible ancillary aftereffect of a scheduler that performs strict-priority scheduling
of a queue, which can aftereffect in lower-priority queues accepting little or no service.
QV See breakthrough value.
RA See Router Advertisement.
QoS pre-classification A action acclimated in routers that are encrypting cartage to admittance departure QoS
actions to be taken on cartage that is actuality encrypted on that router. QoS pre-classification keeps a
copy of anniversary packet to be encrypted in anamnesis continued abundant to booty the adapted departure QoS
actions on that cartage as it leaves that router, because the encrypted cartage cannot be inspected for
QoS actions.
quantum amount The cardinal of bytes in a chain that are removed per aeon in MDRR. Similar
to byte calculation in the custom queuing (CQ) scheduler.
radio administration accession Reduces the bandwidth all-important for radio management
information, such as admission point cachet messages, that is beatific beyond the arrangement by eliminating
redundant administration information.
RADIUS A protocol, authentic in RFC 2865, that defines how to accomplish affidavit between
an authenticator (for example, a router) and an affidavit server that holds a account of usernames
and passwords.
Rapid Per-VLAN Spanning Timberline Plus The aggregate of PVST+ and Rapid Spanning Tree.
It provides subsecond accession time and is accordant with PVST+ and MSTP.
Rapid Spanning Timberline Agreement Authentic in IEEE 802.1w, a blueprint to enhance the
802.1d accepted to advance the acceleration of STP convergence.
RARP See About-face ARP.
RD See Appear ambit or Avenue Distinguisher.
Ready To Accelerate On a consecutive cable, the pin advance set by the DTE to acquaint the DCE that the DTE wants
to accelerate data.
receiver’s advertised window In TCP, a TCP host sets the TCP header’s Window acreage to the
number of bytes it allows the added host to accelerate afore acute an acknowledgement. In effect,
890 Red Alarm
the accepting host, by advertence a accurate window size, grants the sending host the appropriate to send
that cardinal of bytes in a distinct window.
Red Anxiety A T1 anxiety accompaniment that occurs aback a accessory has detected a bounded LOF/LOS/AIS
condition. The accessory in Red anxiety accompaniment again sends a Yellow anxiety signal.
regular announcement A account of interspersed alphanumeric literals and metacharacters that are used
to administer circuitous analogous argumentation to alphanumeric strings. Generally acclimated for analogous AS_PATHs in
Cisco routers.
Reliable Transport Agreement A agreement acclimated for reliable multicast and unicast transmissions.
Used by EIGRP.
remaining bandwidth A CBWFQ and LLQ appellation apropos to the bandwidth on an interface that
is neither aloof nor allocated via a antecedence command.
remote assuming In MPLS, a appellation acclimated to ascertain a assuming that an LSR abstruse from a adjoining LSR.
rendezvous point In the PIM-SM design, the axial administration point to which the multicast
traffic is aboriginal delivered from the antecedent appointed router.
Reply (EIGRP) An EIGRP bulletin that is acclimated by neighbors to acknowledgment to a query. Reply
messages crave an Ack.
reported ambit With EIGRP, the metric (distance) of a avenue as appear by a neighboring
router.
request-to-send/clear-to-send A apparatus that counters collisions acquired by hidden nodes.
If enabled, the base or admission point charge aboriginal accelerate an RTS anatomy and accept a CTS anatomy before
sending anniversary abstracts frame.
Report Suppression apparatus Aback a Concern is accustomed from a router, anniversary host randomly
picks a time amid 0 and the Maximum Acknowledgment Time aeon to accelerate a Report. Aback the
host with the aboriginal time aeon aboriginal sends the Report, the blow of the hosts abolish their
reports.
Response In the ambience of SNMP, the Acknowledgment command is beatific by an SNMP agent, aback to
a manager, in acknowledgment to any of the three types of Get requests, or in acknowledgment to a Set request.
It is additionally acclimated by a administrator in acknowledgment to a accustomed Inform command from addition SNMP
manager. The Acknowledgment holds the value(s) of the requested variables.
Retransmission Timeout With EIGRP, a timer started aback a reliable (to be acknowledged)
message is transmitted. For any neighbor(s) declining to acknowledge in its RTO, the RTP agreement causes
retransmission. RTO is affected based on SRTT.
Reverse ARP A accepted (RFC 903) agreement by which a LAN-attached host can dynamically
broadcast a appeal for a server to accredit it an IP address. See additionally ARP.
RF admission The specific abundance subband on which the radio agenda or admission point is
operating. The RF admission is set in the admission point or ad hoc stations.
RGMP See Router-Port Accumulation Administration Protocol.
RID See router ID.
ROMMON An addition software loaded into a Cisco router, acclimated for low-level debugging
and for countersign recovery.
Root Guard Cisco-proprietary STP affection in which a about-face anchorage monitors for incoming
superior Hellos, and reacts to a above Hello to anticipate any about-face affiliated to that anchorage from
becoming root.
root anchorage The distinct anchorage on anniversary nonroot about-face aloft which the best Hello BPDU is received.
Route Distinguisher A 64-bit addendum to the BGP NLRI field, acclimated by MPLS for the purpose
of authoritative MPLS VPN chump routes altered in animosity of the achievability of overlapping IPv4
address spaces in altered chump networks.
route map A agreement apparatus in Cisco IOS that allows basal programming argumentation to be applied
to a set of items. Generally acclimated for decisions about what routes to redistribute, and for setting
particular characteristics of those routes—for instance, metric values.
route contagion The action of sending an infinite-metric avenue in acquisition updates aback that
route fails.
route redistribution The action of demography routes accepted through one acquisition agreement and
advertising those routes with addition acquisition protocol.
route reflector A BGP affection by which a router learns iBGP routes, and again assiduously them
to added iBGP peers, abbreviation the adapted cardinal of iBGP aeon while additionally alienated routing
loops.
route reflector applicant A BGP router that, alien to it, is aided by a avenue reflector server to
cause all iBGP routers in an AS to apprentice all eBGP-learned prefixes.
route reflector non-client A BGP router in an AS that uses avenue reflectors, but that is not aided
by any RR server.
route reflector server A BGP router that assiduously iBGP-learned routes to added iBGP routers.
Route Tag acreage A acreage aural a avenue access in a acquisition update, acclimated to accessory a generic
number with the route. It is acclimated aback casual routes amid acquisition protocols, acceptance an intermediate
routing agreement to canyon advice about a avenue that is not natively authentic to that
intermediate acquisition protocol. Frequently acclimated for anecdotic assertive routes for clarification by a
downstream acquisition process.
Route Target In MPLS VPNs, a 64-bit Extended Community aisle aspect absorbed to a BGP
route for the purpose of authoritative into which VRFs the avenue is added.
routed interface An interface on a Cisco IOS–based about-face that is advised as if it were an
interface on a router.
Router Advertisement In IPv6, a Router Advertisement bulletin acclimated by an IPv6 router to
send advice about itself to nodes and added routers affiliated to that router.
router ID The 32-bit cardinal acclimated to represent an OSPF router.
Router-Port Accumulation Administration Agreement A Cisco-proprietary Band 2 agreement that enables
a router to acquaint to a about-face which multicast accumulation cartage the router does and does not
want to accept from the switch.
routing atramentous aperture A botheration that occurs aback an AS does not run BGP on all routers, with
synchronization disabled. The routers active BGP may accept they accept alive routes to reach
a prefix, and advanced packets to centralized routers that do not run BGP and do not accept a avenue to
reach the prefix.
RP See affair point.
RPF analysis Designed to break the problems of multicast duplication and multicast routing
loops. For every multicast packet received, a multicast router examines its antecedent IP address,
consults its unicast acquisition table, determines which interface it would use to go in the reverse
direction against the antecedent IP address, compares it with the interface on which the packet was
received, and, if they match, accepts the packet and assiduously it; otherwise, the router drops the
packet.
RPVST+ See Rapid Per-VLAN Spanning Timberline Plus.
RSTP See Rapid Spanning Timberline Protocol.
RT See Avenue Target.
RTO See Retransmission Timeout.
RTP See Reliable Transport Protocol.
RTP attack compression The action of demography the IP, UDP, and RTP headers of a articulation or
video packet, burden them, and again uncompressing them on the accepting router.
RTS See Ready To Send.
RTS/CTS See request-to-send/clear-to-send.
RXBOOT An addition software loaded into a Cisco router, acclimated for basal IP connectivity—
most advantageous aback Flash anamnesis is burst and you charge IP connectivity to archetype a new IOS image
into Flash memory.