Implementing LISP Host Mobility with Extended Subnet
Implementing LISP Host Mobility Extended Subnet
In Below Figure, LAN subnet 10.11.11.0/24 VLAN 100 has been extended between West and East DC. DC switches are said be to xTR and Remote Site is hosting 10.10.10.0/24 subnet. The MS/MR is also configured on same xTR devices in both DC.
Here we will how these DC and Remotes sites are configured as LISP sites and later we will see how traffic flows between them.
- HSRP message must not be exchanged across DC, which will make sure that an active default gateway is present in each DC locations and prevent asymmetric path.
- The Default gateway (VIP) and vMAC must be consistent across DC for that Extended VLAN.
- The L2 extension protocols (OTV or any) must have multicast support over Extended LAN subnet for proper operation of LISP host Mobility in an extended subnet mode.
Sample Configuration & Explanation
Below Both Nexus 7k on West DC and East DC and also each command explanation has been given.
Step1: Enable LISP feature which will make Nexus 7K as ETR while decapsulation LISP traffic received from L3 domain and N7K acts as ITR for encapsulating LISP traffic destined to desired location.
Step2: A global Database mapping to be configured with aggregated subnet that identifies all IP subnets deployed in specific DC. Here 10.11.0.0/16 is mapped with two RLOC IP address each with xTR1 & xTR2 at DC West. The RLOC recommendation is to use loopback IP address. Priority and weight is also configured to insure that inbound traffic can be load-balanced across both DC xTRs.
Step3: Now configuration to define IP address of Map-Servers and MP-Resolvers. Here we have used Map-Server from Both DC and anycast IP address of MR.
Step4: A Dynamic mapping of the mobile subnet is also required , Here Subnet 10.11.11.0/24 is mobile subnet under which host is moved from West Dc to East DC.
Step5: Finally LISP dynamic-eid-policy must be configured under L3 interface ( SVI of VLAN 100 )
Now below configuration also shows about East DC xTR
The Explanation of configuration is same as discussed above, but only few things needs to be noted which makes some difference.
- The global mapping is different from one configured on west DC xTR, on east side it is 10.12.0.0/16.
- Dynamic-eid mapping subnet must me same that is 10.11.11.0/24 which is defined on west xTR. However the RLOC is mapped to east DC RLOC.
- Map-notify-group associated to dynamic-eid mapping must be identical as configured on West DC xTR switches. This is because it will be used for control plane communication by all xTR connected to extended subnet and due to which multicast support must be enabled and configured for this multicast IP.
- HSRP group is same on both DC xTR so that it can give same vMAC address
Remote Site Cisco IOS-xTR configuration:
The Configuration of branch xTR is shown in below figure.
Step 1: Define EID space or subnet and host of this subnet will communicate to DC workload. RLOC address associated to EID prefix may be loopback address, which is 220.127.116.11 with priority 1 and weight 100 which influence the inbound traffic policies or the physical WAN IP can also be used as RLOC addresses.
Step2: Configuration of Map-Server and Map-Resolver Anycast address.
Step3: Enable ITR & ETR functionalities on device.
Map-Server & Map-Resolver N7K Configuration:
Below Figure describes the Map-server and map-Resolver configuration.
Step1: Enable MS& MR functionalities on the device.
Step2: Configure Loopback IP address for Map-Resolver and Map-Server.
Step3: Configure Remote Site Branch
Step4: Configure West & East DC Sites.
Here in above configuration accept-more-specifics is associated to both DC eid-prefix , this is mandatory configuration where LISP host mobility is enabled because /32 prefix which are part of larger prefix will be registered by DC xTRs.