
When issuing the `show ip nhrp` command, the output includes a list of flags that indicate the state of [NHRP](/nhrp).

An example of output of this command can be seen below:

```
Router# show ip nhrp
10.0.0.2/32 via 10.0.0.2, Tunnel0 created 00:17:49, expire 00:01:30
  Type: dynamic, Flags: unique registered used 
  NBMA address: 172.17.0.2 
  Group: test-group-0
10.0.0.3/32 via 10.0.0.3, Tunnel0 created 00:00:11, expire 01:59:48
  Type: dynamic, Flags: unique registered used 
  NBMA address: 172.17.0.3 
  Group: test-group-0
11.0.0.2/32 via 11.0.0.2, Tunnel1 created 00:17:49, expire 00:02:10
  Type: dynamic, Flags: unique registered used 
  NBMA address: 172.17.0.2 
  Group: test-group-1
```

Note that for each NHRP association, a list of flags is shown.  These flags have the following meanings:

* **authoritative**--Indicates that the NHRP information was obtained directly from the Next Hop Server or router that maintains and is authoritative for the NBMA-to-IP address mapping for a particular destination.
* **implicit**--Indicates that the local node learned about the NHRP mapping entries from the source mapping information of an NHRP resolution request received by the local router, or from an NHRP resolution packet being forwarded through the local router.
* **local**--Indicates NHRP mapping entries that are for networks local to this router (that is, serviced by this router). These flag entries are created when this router answers an NHRP resolution request that has this information and is used to store the transport (tunnel) IP address of all the other NHRP nodes to which it has sent this information.
* **nat**--Indicates that the remote node (NHS client) supports the new NHRP NAT extension type for dynamic spoke-spoke tunnels to/from spokes behind a NAT router.
* **negative**--For negative caching, indicates that the requested NBMA mapping has not yet been or could not be obtained.
* (no socket)--Indicates that the NHRP mapping entries will not trigger IPsec to set up encryption because data traffic does not need to use this tunnel. Later, if data traffic needs to use this tunnel, the flag will change from a “(no socket)” to a “(socket)” entry and IPsec will be triggered to set up the encryption for this tunnel.
* **registered**--Indicates that the mapping entry was created in response to an NHRP registration request.
* **router**--Indicates that NHRP mapping entries for a remote router (that is accessing a network or host behind the remote router) are marked with the router flag.
* **unique**--NHRP registration requests have the unique flag set on by default. This flag indicates that an NHRP mapping entry cannot be overwritten by a mapping entry that has the same IP address and a different NBMA address. 
* **used**--When data packets are process-switched and this mapping entry was used, the mapping entry is marked as used. The mapping database is checked every 60 seconds. If the used flag is set and more than 120 seconds remain until expire time, the used flag is cleared. If fewer than 120 seconds are left, this mapping entry is “refreshed” by the transmission of another NHRP resolution request.


NHRP show ip nhrp flags

Multicast PIM Route Pruning and SPT-Threshold

Multicast PIM dense mode

Multicast PIM neighbors are stateless

Multicast PIM send-rp-announce-scope

Multicast PIM sparse mode Rendezvous Point (RP)

Multicast PIM sparse mode

Multicast PIM sparse-dense mode

Multicast PIM what triggers an assert forwarder election

Multicast PIM with multiple RPs

Multicast PIM with multiple mapping-agents

Multicast PIM-assert forwarder election

Multicast SPT and RPT

Multicast bidirectional PIM advantages

Multicast boundary filtering - filter auto RP

Multicast enabling Bidir in BSR mode

Multicast ip pim autorp listener

Multicast ip pim rp-address override

Multicast load splitting across equal-cost paths

Multicast local subnetwork address range

Multicast mapping IP to MAC addresses

Multicast mapping agent IGMP membership report

Multicast ping on a Nexus device

Multicast using Anycast RP with Auto-RP and BSR

Multicast

NAT - Translation Table

NAT - Twice NAT

NAT - Understanding debug nat detailed output

NAT - Virtual Interface (NVI)

NAT - What is Policy NAT

NAT - add-route keyword

NAT - ip nat inside destination

NAT - ports used for translation

NAT - show NAT translations

NAT - translate address not directly connected to edge device

NAT Extendable on Cisco IOS

NAT Order of Operation

NAT address naming conventions

NAT and IPv6

NAT how port numbers are chosen when using PAT

NAT intra-VRF NAT

NAT port forwarding - specifying outside IP address

NAT prefix-length keyword on nat pool command

NAT vrf-aware

NBAR classifies only established sessions

NETCONF

NHRP - Authentication

NHRP - Destination Protocol Address

NHRP - Holding Time

NHRP - resolution redirect from hub

NHRP

NIC Promiscuous Mode

NTP - securing with MD5 authentication and a Windows NTP server

NTP poll interval

NTP server and client and the master command

NTP troubleshooting and debugging tools

NTP versions 3 and 4

Native VLAN Traffic Flow on Trunk Ports

Native VLAN

Native VLANs and untagged frames

NetFlow - Flexible NetFlow

NetFlow - Flow Samplers

NetFlow - applying to an SVI

NetFlow - what is a flow

NetFlow local cache size

NetFlow

Network - BUM Traffic

Network - Discontiguous or Discontinuous

Network - Discontiguous

Network - Example of communication, encapsulation, and decapsulation, between hosts

Network - Flapping

Network - Layer 3 network

Network - Monitoring multiple IPs of a single device with Observium

Network - Observium vs LibreNMS

Network - Simultaneous network traffic handling

Network - Transient traffic

Network - Two Way Active Measurement Protocol (TWAMP)

Network - control plane

Network - data plane

Network Address Translation (NAT)

Network Collisions

Network Design - Choosing a technology for multiple datacenter topology

Network Design - Load Balancing vs Load Sharing

Network Design - Spine and leaf architecture

Network Design - Switch oversubscription ratios

Network Design - Traffic Engineering

Network Design - on-premises and off-premises

Network Design Achieving Redundancy with PE Devices

Network Design Considerations Involving PE and P Routers

Network Management Areas

Network Time Protocol (NTP)

Network design - confine VLANs to as few access switches as possible

Network planes

Networking - Understanding Chassis devices

Networking - what is a socket

Networks - Overlay Network

Networks - Overlay Transport Virtualization (OTV)

Networks - Spanning Layer 2 networks across remote sites

Networks - Underlay Network

Next Generation Multicast Virtual Private Network (NG-MVPN)