Have you contact broadband provider on the 871 side to rule out any issues on the link? what broadband ADSLAM pppoa? start first rulling out physical issues WAN interface, LAN interface stats and work your way up, is this is something that suddenly developped? from what you post indicates it seems this tunnel have been fine, it could be broadband link issues but fist investigate with provider to go the next step.
what do you see in 871 router logs in terms of links, turn on logging informational before staring debugg proceedures.
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...