NHRP
NHRP — Next-Hop Resolution Protocol
NBMA — Non-Broadcast Multi-Access Network
- Network connections you could make
- If you knew how to address the packet
NBMA Address
- AKA transport address
- DMVPN, public Internet address
- Frame-relay, DLCI
NHS — Next Hop Server
- Typically the hub router
- Supports dynamic registration
NHC — Next Hop Client
- Dynamically register with the NHS
Protocol Address
- AKA overlay address
- Usually a /24
Config
Hub
interface Tunnel1
ip address 192.168.100.1 255.255.255.0
no ip redirects
ip nhrp network-id 111
!
! This is the NBMA address.
!
tunnel source 10.0.110.1
tunnel mode gre multipoint
Spoke
interface Tunnel1
ip address 192.168.100.2 255.255.255.0
no ip redirects
!
! Logical address, then NBMA address
!
ip nhrp map 192.168.100.1 10.0.110.1
ip nhrp map multicast 10.0.110.1
ip nhrp network-id 111
ip nhrp nhs 192.168.100.1
tunnel source 10.0.120.2
tunnel mode gre multipoint
Verification
This hub knows about two sites, that have dynamically registered their NBMA addresses.
hub# show ip nhrp brief
****************************************************************************
NOTE: Link-Local, No-socket and Incomplete entries are not displayed
****************************************************************************
Legend: Type --> S - Static, D - Dynamic
Flags --> u - unique, r - registered, e - temporary, c - claimed
a - authoritative, t - route
============================================================================
Intf NextHop Address NBMA Address
Target Network T/Flag
-------- ------------------------------------------- ------ ----------------
Tu1 192.168.100.2 10.0.120.2
192.168.100.2/32 D/r
Tu1 192.168.100.3 10.0.130.3
192.168.100.3/32 D/r
References
Cisco - IOS IP Routing: NHRP Command Reference - IOS XE 16
RFC 2332: NBMA Next Hop Resolution Protocol (NHRP) | RFC Editor