I am trying to set up a GRE tunnel so I can send routing updates and QOS between sites. Right now, we have a 2611XM and an 871W. How can I configure this if the 871W router is using DHCP for the WAN (2611XM is a static address)? I'm suck trying to figure out what to do for the "tunnel destination" on the 2611XM.
NHRP allows the peers to have dynamic addresses (ie: Dial and DSL) with GRE / IPsec tunnels.
What you do on the 2611 is to configure mGRE tunnel mode, and on both sides you configure NHRP in order for the 871 to register with the 2611.
When you use this with ipsec, you can for example configure QoS groups in the ISKAMP profiles.