To keep the tunnel up you need traffic to be flowing over it. The easiest way to do this is to setup your head-end router (or a host on the head-end network) as a NTP server (Network Time Protocol). Then setup your spokes as NTP clients and source the NTP packets from the inside interface, they will send regular, very small NTP update packets to the head-end which will keep your tunnel up. This has the added advantage of keeping all your times in sync for logging purposes, etc.
On the head-end router do the following:
ntp master 5
and on each remote site router then do:
ntp server source
This will make each remote site router send NTP packets, sourced from its inside interface, to the inside interface of the hub router. Assuming that this matches your crypto ACL this traffic will keep the tunnel up.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...