Cisco Nexus 7000 Series Configuration Manual page 117

Configuring LISP Extranets
with host 10.1.2.2 because they are connected to the same IID domain (IID 100), but cannot communicate
with host 10.3.3.3 as it is connected to a different IID domain (IID 300).
Using the LISP Extranets feature, a user can establish a leaking policy, wherein the traffic can cross the IID
boundaries. For example, if host 10.1.1.1 needs to communicate/share policies with host 10.3.3.3, network
administrators can configure an extranet policy on the LISP Mapping System, xTR3 will dynamically discover
the policy and allow host 10.1.1.1 and host 10.3.3.3 to talk to each other across IID boundaries.
Packet Flow in LISP Extranets Through Map Server Policies
In the following diagram, H1 (10.1.1.1) wants to send packet to H2 (10.3.3.3). Both hosts reside in different
IID domains, but a LISP extranet policy setup in the Mapping System (MS) allows the traffic to cross the IID
boundaries.
Figure 21: Packet Flow in LISP VRF Leaking
1. H1 (10.1.1.1) on IID 100 sends a packet to H2 (10.3.3.3) on IID 300.
2. The packet first arrives on IID 100 residing on xTR1.
IID 100 on xTR1 determines it is a cache miss and sends a map-request to the Mapping System.
3. Map server receives the map request from xTR1 for mapping details on H2.
4. xTR1 receives the map-reply from the MS. It sees that it contains a valid Home IID within the map reply.
• The MS uses its extranet policy configuration to determine if communication is allowed between
H1 on IID 100 and H2 on IID 300.
• The MS permits communication between these two IIDs. MS sends a map-reply back to IID 100 on
xTR1, with an additional parameter called Home IID. In this example the Home IID is IID 300.
• The Home IID is different from the IID (IID 100) that was used to send the map request.
• xTR1 learns this mapping as an extranet route.
Cisco Nexus 7000 Series NX-OS LISP Configuration Guide
Use Case for LISP Extranets
105