We have DMVPN in hub-n-spoke model. Hub has redundant Internet connections, a T1 and cable. Some of the remotes also have redundant Internet access, a primary and backup.
Tunnel 10 on hub and spokes is used for back up. Tunnel 20 is used as primary. Spoke are configured to prefere routes they learned from tunnel 20. When tunnel 20 is up on both sides, all works well.
however, when we take down tunnel 20 on a spoke, I see NHRP, NHS, and EIGRP relationship as they should be. Routing table on the spoke is populated using routes learned over tunnel 10 and routing between two routers, hub and spoke, is in place.
Each router has a switch connected. Problem is we can no loger get to far end switch over tunnel 10. debugging shows that switch connected to hub router receives and replies to pings from switch at spoke site, but the replies do not make their way back. Echo-replies are forwarded from hub switch to hub router but they never make it way back to spoke switch.