LISP and VXLAN Flashcards
Which RFC is LISP specified in?
RFC 6830
What protocol enables separation of an endpoint’s identity and its location?
Locator/ID Separation Protocol (LISP)
What is one of LISP’s greatest limitations at Layer 2?
LISP discards the L2 Ethernet header; it only supports L3 overlay.
What is an overlay technology that is a way to deploy an L2 overlay network over a L3 underlay?
VXLAN
For LISP overlays, what term identifies an endpoint?
Endpoint identifier (EID) address - IPs or prefixes
What is an RLOC address?
Routing Locator - in LISP, these IPs identify different routers in the network that may also represent different sites.
What is the role of an ingress tunnel router (ITR)?
ITRs act as a LISP site edge device. It receives packets from internal hosts (site-facing interfaces), encapsulates them to remote LISP sites or natively routes them to non-LISP sites.
When an ITR receives a packet destined for an EID, where does it look for the EID-to-RLOC mapping?
It first looks in its mapping cache. If it cannot be found in its cache, then the ITR sends a Map-Request to one of its Map Resolvers (MR). It then receives a Map-Reply with the EID-to-RLOC mapping.
What is the role of an egress tunnel router (ETR)?
- ETRs act as a LISP site edge device. It receives packets from outside the site (core-facing interfaces), de-encapsulates LISP packets, then forwards them to local EIDs at the site.
- ETRs will periodically send Map-Register messages to its map servers, to map local EIDs to the ETR’s site.
What is the role of the map server (MS)?
- MSs keep track of the EID-to-RLOC database for the network’s sites. It accepts Map-Register requests from ETRs.
- EID prefixes are aggregated by MSs, and advertised to the ALT router with BGP
What is the role of the map resolver (MR)?
- MRs accept Map-Requests by ITRs, decapsulates them, and forwards them over to the ALT router toward the ETRs responsible for the EIDs being requested.
What is the role of a Proxy ITR (PITR)?
- PITRs handle EID-to-RLOC lookups and LISP encapsulation for non-LISP-capable sites.
- Advertises some or all of the non-routable EID prefixes to the non-LISP-capable sites
What is the role of a Proxy ETR (PETR)?
- PETRs handle ETR functions for non-LISP sites. Typically used when a LISP site needs to send traffic to non-LISP sites, but its access network (ISP) can’t accept non-routable EIDs as packet sources.
- With dual stacking, PETRs can facilitate communication between EIDs in one address family and RLOCs within a different address family to communicate to each other.
What is the role of an ALT router?
- Not present in all mapping database deployments
- ALT routers accept EID prefixes and advertise an aggregated EID prefix, which is a function that MS/MRs may do as well
What is a device called that performs both ITR/ETR functions?
xTR
What is a device called that performs both PITR and PETR functions?
PxTR
What are two different host mobility models offered by LISP?
- LISP host mobility with an extended subnet
- LISP host mobility across subnets
Explain LISP host mobility.
EIDs (endpoints) are able to move across sites without impacting the routing or necessitating the injection of host routes.
Explain LISP host mobility with an extended subnet
This is when a subnet/VLAN is no longer associated within a single location. When a host in one subnet moves from one site to another, it can retain its original IP while not impacting the routing. The EID-RLOC is updated dynamically, and traffic is forwarded to the new site of the EID.
Explain LISP host mobility across subnets
An EID can move to another subnet while retaining its original IP address. A LISP router can see an EID not from one of its subnets, and still register the new EID-to-RLOC mapping
What are 3 benefits of VXLAN?
1) Multitenant segments can be flexibly placed through a data center
2) VXLAN supports 16 million coexistent segments, identified by their VXLAN network identifiers (VNIs)
3) Since VXLAN use L3 as the underlay network, it can take advantage of L3 routing, ECMP, and link aggregation. Unlike normal L2 that uses STP which blocks redundant network paths
What is a difference in usage between Cisco OTV (Overlay Transport Virtualization) and VXLAN?
OTV: Provides L2 connectivity over L3 between two data centers
VXLAN: Intended for use within a single data center
How big is the VXLAN header?
8 bytes
What is the role of a VTEP when using VXLAN?
Virtual tunnel endpoint (VTEP)
Maps devices in local segments to VXLAN segments. Performs encapsulation and decapsulation of the L2 traffic.
What is the function of a VXLAN gateway?
VXLAN L2 Gateway - Enables VLAN-to-VXLAN connectivity. It is a VTEP that combines VXLAN and VLAN in one common L2 domain.
VXLAN L3 gateway (AKA VXLAN router) - Routes between different VXLAN segments. Routes frames of one VNI to another,
What is the VXLAN Group Policy Option (VXLAN-GPO)?
The latest version of VXLAN. Adds a Group Police ID header to carry Scalable Group Tags (SGT) used in SD-Access for different policies.
What is the source port and destination for VXLAN-GPO?
Source - hash value created using original source information
Destination - 4789 always
What transport protocol does VXLAN-GPO use?
UDP
