If I have 2 routers communicating with each other over a DMVPN tunnel and the NHRP holdtime expires, would that cause the communication to be reset? I am wandering if this would cause an issue if there was a VOIP call in progress between 2 branch offices where the call may get dropped?
Hi Sukanya, we have Cisco VOIP phones at our office with the Cisco Unity Express residing at the adjacent office. I winded the NHRP holdtime down to 3 minutes and kept the phone on during this time....there was no breaks when the NHRP timer expires on the router. It actually resets itself a few seconds before it is set to expire. The dialtone never dropped. Can someone confirm this is how it's supposed to work?
I just found this piece of text on Cisco site http://www.cisco.com/en/US/customer/tech/tk583/tk372/technologies_white_paper09186a008018983e.shtml
If the NHRP mappings are used within the last minute before expiring, then an NHRP resolution request and reply will be sent to refresh the entry before it is deleted. Otherwise, the NHRP mapping will be deleted and that will trigger IPsec to clear the IPsec SAs.
That confirms the traffic will not be dropped.
If NHRP hold time expires, it will take down your VPN; however if it receives mapping before or even just before ( as you mentioned ) it can continue...
However, if it expire it will definately take down your VPN session...