Redistribution OSPF to NHRP

[okandaur89]

While troubleshooting some routing issue, I noticed a strange output of "show ip protocols" of my 3945 router.

It looks like nhrp is used as a routing protocol and another routing protocol ospf is redistributed into it.

NHRP is used for creating DMVPN tunnels in my network, this 3945 is DMVPN hub.

3945-WAN-1#sh ip proto
*** IP Routing is NSF aware ***
Routing Protocol is "nhrp"
  Redistributing: static, ospf 1
  Maximum path: 0
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: (default is 0)

Does this output mean that nhrp can propagate routing info redistributed from ospf to its spokes? If so, what administrative distance or another priority over other routing protocols does nhrp have?

[ManishK]

NHRP resolved routes have a low default admin distance of 250. NHRP registered and registration summary routes have default admin distances of 15 and 16 respectively.

[Giuseppe Larosa]

Hello @okandaur89 ,

NHRP is not a routing protocol but rather the equivalent of ARP in an NBMA generalized IP internetwork where a logic flat subnet (the one used by MGRE tunnel in DMVPN) is actually spread over mutiple different IP addresses.

I would consider this output just as a cosmetc bug

We see also two fields

>>

Maximum path: 0

And

Distance: (default is 0)

And an empty list of gateways  as expected.

each NHRP client registers with NHRP server to tell what is its NBMA address and its private internal address.

Then over the logic common subnet we can run a routing protocol either OSPF or EIGRP but NHRP just does the above.

Hope to help

Giuseppe

[MHM Cisco World]

NHRP is not routing protocol,
DMVPN tunnel is build and IP address use in tunnel is consider as direct connect between Hub and Spoke.
Now you can config EIGRP or BGP (these recommend from Cisco) as routing protocol to make host behind the Spoke can access to resource behind the hub.