Information About LISP VM Mobility
Locator/ID Separation Protocol (LISP) Virtual Machine (VM) mobility enables IP end points to change locations while keeping their assigned IP addresses. Because LISP separates the location information (RLOCs) from the identity information (EID), devices can change locations dynamically. RLOCs remain associated with the topology and are reachable by traditional routing. EIDs can change locations dynamically and are reachable through different RLOCs, depending on where an EID attaches to the network.
The LISP Tunnel Router (xTR) dynamically detects VM moves based on data plane events. LISP VM Mobility compares the source IP address of the host traffic received at the LISP router against a range of prefixes that are allowed to roam. The IP prefixes of roaming devices within the range of allowed prefixes are referred to as the dynamic EIDs. When a new xTR detects a move, it updates the mappings between EIDs and RLOCs. Traffic is redirected to the new locations without causing any disruption to the underlying routing. When deployed at the first-hop router, LISP VM Mobility provides adaptable and comprehensive first-hop router functionality to service the IP gateway needs of the roaming devices that relocate.
LISP VM Mobility allows any IP addressable device to move and keep the same IP address in the following two scenarios:
VM Mobility with LAN extensions
The device moves to a new location on a subnet that has been extended with Overlay Transport Virtualization (OTV) or another LAN extension mechanism.
VM Mobility across subnets
The device moves off of a subnet to a new subnet.
Dynamic EIDs
A device that moves to another subnet or extended subnet is a roaming device. The IP address of this roaming device is within the dynamic-EID prefix. A LISP xTR configured with LISP VM mobility and dynamic EIDs is a LISP-VM router. The LISP-VM router dynamically determines when a dynamic EID moves on or off one of the directly connected subnets on the LISP-VM router. The IP addresses of the LISP-VM router are the locators (RLOCs) used to encapsulate traffic to and from the dynamic EID. When a dynamic EID roams, the new LISP-VM router needs to detect the newly moved-in VM and process the following updates:
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Update the Map Server (MS) with the new locators for the EID.
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Update the Ingress Tunnel Routers (ITRs) or Proxy ITRs (PITRs) that have cached the EID.
To detect VM moves, LISP-VM router compares the source address in a received packet with the range of prefixes configured as dynamic EIDs for the interface that the data packet is received on. Once the LISP-VM router detects a move and registers the dynamic EID to the MS, the new LISP-VM router also needs to update the map caches on the other LISP domain ITRs and PITRs.
VM-Mobility with LAN Extensions
LISP VM Mobility supports virtual machine (VM) movement in a network that uses LAN extension mechanisms such as OTV. The LISP-VM router detects the mobile EIDs (VMs) dynamically and updates the LISP mapping system with the new EID-RLOC mapping. LISP can coexist with LAN extensions such as OTV to provide dynamic move detection and updates that are transparent to the host and provide a direct data path to the new location of the mobile VM. The VM move requires no routing reconvergence or DNS updates.
The LISP-VM router detects new VM move events if it receives a data packet from a source that matches the dynamic EID configured for that interface. Once the LISP-VM router detects a dynamic EID, the LISP-VM router triggers an update to the map server with the database mapping details from the dynamic-EID map configuration.
The LISP-VM router continues to register the dynamic EID as long as the source continues to be active. The dynamic-EID registration times out based on server inactivity. See Configuring VM Mobility with VLAN Extensions.
VM Mobility Across Subnets
In a network without LAN extension mechanisms, the LISP VM router can detect the dynamic-EIDs (VMs) across subnets with automated move detection and map-cache updates that provide a direct data path to the new location of the mobile VM. Off-subnet connections (connections between the moved VM and other devices that are not on the local subnets) are maintained across the move and require no routing re-convergence or DNS updates.
The LISP-VM router detects a VM move if it receives any data packet that is not from one of its configured subnets and that is within the range of prefixes configured as dynamic EIDs for the receiving interface. The LISP-VM router registers the new dynamic-EID-RLOC mapping to the configured map servers associated with the dynamic EID. See Configuring VM Mobility Across Subnets.