OSPF Do Not Age (DNA) Flag


Demand circuits are network segments where you are charged based on connect time and/or bytes or packets transmitted. Examples are ISDN, X.25 SVCs, and dial-up lines.

Running (routing) protocols over these circuits can be an issue. Hello packets from routing protocols such as [OSPF](/ospf) can cause these circuits to remain open and result in unwanted usage charges.

There are solutions for this such as:

- OSPF Demand Circuit
- Static routes instead of routing protocols.
- Routing protocol timer tuning

Demand Circuits

DHCP snooping rate limiting best practice

DHCP trusted and untrusted ports

DHCP

DHCPv6 - Modes of Operation

DHCPv6 - determining the IPv6 prefix assigned to an interface

DHCPv6 lease times on a Cisco IOS device

DHCPv6 relay agent

DMVPN - Dual-Hub Single-Cloud with redundant spoke links config guidelines

DMVPN - IPsec encryption order of operations

DMVPN - NHRP purge request

DMVPN - NHRP session attributes

DMVPN - OSPF and multiple areas

DMVPN - Phase 2 BGP peerings

DMVPN - Phase 2 EIGRP neighbor adjacencies

DMVPN - Phase 2 OSPF neighbor adjacencies

DMVPN - Phase 2 and multicast traffic

DMVPN - Phase 2 and summarization

DMVPN - Using the GRE tunnel key

DMVPN - What is the best routing protocol to use

DMVPN - mappings on hub and spokes

DMVPN - multicast commands

DMVPN - nhrp map and nhs command syntax

DMVPN - spoke redundancy

DMVPN - using a default route

DMVPN Dual Cloud Path Selection Using IGP Metrics

DMVPN State of a tunnel

DMVPN dual hub dual cloud

DMVPN dual hub single cloud

DMVPN hierarchical topology

DMVPN redundancy options

DMVPN with more than two hubs

DMVPN

DNS - Authoritative Flag

DNS - Authoritative Server

DNS - Caching

DNS - Recursive Resolver

DNS - What is a delegation zone

DNS - stub zone

DNS - understanding zones

DNS cache windows PC

DSL - Asymmetric Digital Subscriber Line (ADSL)

DTP - Sending of Frames

DTP - best practice to disable

DTP - how to disable

Debug Condition Command Restrictions in Cisco IOS

Debug IP Routing

Decrypt IPSec ESP traffic with Wireshark

Demarcation point

Difference between per-prefix LFA and per-link based LFA

Differences between CCIE and CCDE lab exams

Diffserv recommended configuration

Distribute-lists - using route maps to set attributes

Distribute-lists and named extended ACLs

ECMP Multicast Routing Cisco Nexus Switches

EEM - action mail

EEM - exit status variable

EEM Cisco Embedded Event Manager

EEM Matching a string within CLI output

EEM sync and skip keywords

EIGRP - Advertised metric is cumulative

EIGRP - Advertising a route using the network command

EIGRP - DUAL Algorithm and FD Set to Infinity

EIGRP - External routes from different ASes

EIGRP - Feasible Successors and the DUAL Algorithm

EIGRP - Hello interval and Hold time

EIGRP - Hop Count

EIGRP - Message TTL value of 2

EIGRP - Metric Equation Multipliers

EIGRP - Network command syntax

EIGRP - Queries

EIGRP - RTP's reliable message exchange process

EIGRP - Reliable Multicast

EIGRP - Router ID and loop prevention

EIGRP - SIA Process and RTP retry attempts

EIGRP - Source of values for metric calculation

EIGRP - Static neighbors over any L2 technology

EIGRP - Stub Router

EIGRP - Stub default behavior

EIGRP - Stub router types

EIGRP - Summarization per interface

EIGRP - Understanding Advertised Distance (AD)

EIGRP - Update message exchange process

EIGRP - Viewing RTP in Wireshark

EIGRP - af-interface configuration mode

EIGRP - how metrics are sent in updates

EIGRP - internal vs external routes

EIGRP - metric computation method

EIGRP - metric equation

EIGRP - named mode name

EIGRP - network command with no wildcard mask

EIGRP - redistribute connected and static routes

EIGRP - shutdown command

EIGRP - stub site function

EIGRP Create and advertise a default route

EIGRP Feasibility condition

EIGRP Header

Demand Circuits

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