Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring IP Addressing
IP Addressing Examples
IPC-58
Cisco IOS IP Configuration Guide
NHRP on a Multipoint Tunnel Example
With multipoint tunnels, a single tunnel interface may be connected to multiple neighboring routers.
Unlike point-to-point tunnels, a tunnel destination need not be configured. In fact, if configured, the
tunnel destination must correspond to an IP multicast address. Broadcast or multicast packets to be sent
over the tunnel interface can then be sent by sending the GRE packet to the multicast address configured
as the tunnel destination.
Multipoint tunnels require that you configure a tunnel key. Otherwise, unexpected GRE traffic could
easily be received by the tunnel interface. For simplicity, we recommend that the tunnel key correspond
to the NHRP network identifier.
In the following example, routers A, B, C, and D all share a common Ethernet segment. Minimal
connectivity over the multipoint tunnel network is configured, thus creating a network that can be treated
as a partially meshed NBMA network. Due to the static NHRP map entries, Router A knows how to reach
Router B, Router B knows how to reach Router C, Router C knows how to reach Router D, and Router D
knows how to reach Router A.
When Router A initially attempts to send an IP packet to Router D, the packet is forwarded through
Routers B and C. Through NHRP, the routers quickly learn the NBMA addresses of each other (in this
case, IP addresses assigned to the underlying Ethernet network). The partially meshed tunnel network
readily becomes fully meshed, at which point any of the routers can directly communicate over the
tunnel network without their IP traffic requiring an intermediate hop.
The significant portions of the configurations for routers A, B, C, and D follow:
Router A Configuration
interface tunnel 0
no ip redirects
ip address 11.0.0.1 255.0.0.0
ip nhrp map 11.0.0.2 10.0.0.2
ip nhrp network-id 1
ip nhrp nhs 11.0.0.2
tunnel source ethernet 0
tunnel mode gre multipoint
tunnel key 1
interface ethernet 0
ip address 10.0.0.1 255.0.0.0
Router B Configuration
interface tunnel 0
no ip redirects
ip address 11.0.0.2 255.0.0.0
ip nhrp map 11.0.0.3 10.0.0.3
ip nhrp network-id 1
ip nhrp nhs 11.0.0.3
tunnel source ethernet 0
tunnel mode gre multipoint
tunnel key 1
interface ethernet 0
ip address 10.0.0.2 255.0.0.0
Router C Configuration
interface tunnel 0
no ip redirects
ip address 11.0.0.3 255.0.0.0
ip nhrp map 11.0.0.4 10.0.0.4