Static Routing

Objective:

Design & develop a computer network between 3 routers in three buildings, using static routing.

Setup:

I have taken several steps to establish static routing between routers A, B, C are given below:

Router A: Network address 192.168.1.0 is used for hosts of the router A. PC 0 and PC 1 are connected through a switch ip configuration of 192.168.1.2 and subnet mask is 255.255.255.0 and 192.168.1.3 and subnet mask is 255.255.255.0. For the cable which connects router A with router B is configured with the ip address 192.168.4.1 and subnet mask is 255.255.255.0. Gateway address used for hosts of router A network is 192.168.1.1 and subnet mask is 255.255.255.0.

Router B: Network address 192.168.2.0 is used for hosts of the router B. PC 2 and PC 3 are connected through a switch ip configuration of 192.168.2.2 and subnet mask is 255.255.255.0 and 192.168.2.3 and subnet mask is 255.255.255.0. For the cable which connects router B with router A is configured with the ip address 192.168.4.2 and subnet mask is 255.255.255.0 and for the cable which connects router B with router C is configured with the ip address 192.168.5.1 and subnet mask is 255.255.255.0. Gateway address used for hosts of router B network is 192.168.2.1 and subnet mask is 255.255.255.0.

Router C: Network address 192.168.3.0 is used for hosts of the router A. PC 4 and PC 5 are connected through a switch ip configuration of 192.168.3.2 and subnet mask is 255.255.255.0 and 192.168.3.3 and subnet mask is 255.255.255.0. For the cable which connects router C with router B is configured with the ip address 192.168.5.2 and subnet mask is 255.255.255.0. Gateway address used for hosts of router C network is 192.168.3.1 and subnet mask is 255.255.255.0.

Network Diagram:

Commands in the routers:

Defining Routes:

Router A:

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.4.2

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.4.2

Router B:

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.4.1

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.5.2

Router C:

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.5.1

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.5.1

Objective:

Design & develop a computer network between 4 routers situated in different places, using static routing with redundancy.

Setup:

I have taken several steps to establish static routing between routers A, B, C, D are given below:

Router A: Network address 192.168.1.0 is used for hosts of the router A. PC 1 is connected through a switch ip configuration of 192.168.1.2 and subnet mask is 255.255.255.0. For the cable which connects router A with router B is configured with the ip address 192.168.5.1 and subnet mask is 255.255.255.0 and router C is configured with the ip address 192.168.6.2 and subnet mask is 255.255.255.0.There is another router D and For the cable which connects router A with router D is configured with the ip address 192.168.10.1 and subnet mask is 255.255.255.0 and the gateway address used for hosts of router A network is 192.168.1.1 and subnet mask is 255.255.255.0.

Router B: Network address 192.168.3.0 is used for hosts of the router B. PC 2 is connected through a switch ip configuration of 192.168.3.2 and subnet mask is 255.255.255.0. For the cable which connects router B with router A is configured with the ip address 192.168.5.2 and subnet mask is 255.255.255.0 and router C is configured with the ip address 192.168.9.2 and subnet mask is 255.255.255.0.There is another router D and For the cable which connects router A with router D is configured with the ip address 192.168.8.1 and subnet mask is 255.255.255.0 and the gateway address used for hosts of router B network is 192.168.3.1 and subnet mask is 255.255.255.0.

Router C: Network address 192.168.2.0 is used for hosts of the router C. PC 3 is connected through a switch ip configuration of 192.168.2.2 and subnet mask is 255.255.255.0. For the cable which connects router C with router B is configured with the ip address 192.168.9.1 and subnet mask is 255.255.255.0 and router A is configured with the ip address 192.168.6.1 and subnet mask is 255.255.255.0.There is another router D and For the cable which connects router A with router D is configured with the ip address 192.168.7.2 and subnet mask is 255.255.255.0 and the gateway address used for hosts of router A network is 192.168.2.1 and subnet mask is 255.255.255.0.

Router D: Network address 192.168.4.0 is used for hosts of the router D. PC 4 is connected through a switch ip configuration of 192.168.4.2 and subnet mask is 255.255.255.0. For the cable which connects router D with router B is configured with the ip address 192.168.8.2 and subnet mask is 255.255.255.0 and router C is configured with the ip address 192.168.7.2 and subnet mask is 255.255.255.0.There is another router A and For the cable which connects router D with router A is configured with the ip address 192.168.10.2 and subnet mask is 255.255.255.0 and the gateway address used for hosts of router A network is 192.168.4.1 and subnet mask is 255.255.255.0.

Network Diagram:

Commands in the routers:

Defining Routes:

Router A:

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.6.1 10

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.10.2 11

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.5.2 12

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.5.2 13

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.10.2 14

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.6.1 15

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.10.2 16

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.5.2 17

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.6.1 18

Router B

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.8.2 10

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.9.1 11

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.5.1 12

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.5.1 13

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.9.1 14

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.8.2 15

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.9.1 16

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.8.2 17

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.5.1 18

Router C

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.6.2 10

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.9.2 11

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.7.1 12

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.7.1 13

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.9.2 14

Router(config)#ip route 192.168.4.0 255.255.255.0 192.168.6.2 15

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.9.2 16

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.7.1 17

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.6.2 18

Router D

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.7.2 10

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.10.1 11

Router(config)#ip route 192.168.2.0 255.255.255.0 192.168.8.1 12

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.8.1 13

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.10.1 14

Router(config)#ip route 192.168.3.0 255.255.255.0 192.168.7.2 15

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.10.1 16

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.7.2 17

Router(config)#ip route 192.168.1.0 255.255.255.0 192.168.8.1 18

IPLC

An IPLC (international private leased circuit) is a point-to-point private line used by an organization to communicate between offices that are geographically dispersed throughout the world. An IPLC can be used for Internet access, business data exchange, video conferencing, and any other form of telecommunication.

Virtual private LAN service

Virtual private LAN service (VPLS) is a way to provide Ethernet based multipoint to multipoint communication over IP/MPLS networks. It allows geographically dispersed sites to share an Ethernet broadcast domain by connecting sites through pseudo-wires. The technologies that can be used as pseudo-wire can be Ethernet over MPLS, L2TPv3 or even GRE. There are two IETF standards track RFCs (RFC 4761 and RFC 4762) describing VPLS establishment.VPLS is a virtual private network (VPN) technology. In contrast to L2TPv3, which allows only point-to-point layer 2 tunnels, VPLS allows any-to-any (multipoint) connectivity. In a VPLS, the local area network (LAN) at each site is extended to the edge of the provider network. The provider network then emulates a switch or bridge to connect all of the customer LANs to create a single bridged LAN. Since VPLS emulates a LAN, full mesh connectivity is required. There are two methods for full mesh establishment for VPLS: using BGP and using Label Distribution Protocol (LDP). The "control plane" is the means by which provider edge (PE) routers communicate for auto-discovery and signaling. Auto-discovery refers to the process of finding other PE routers participating in the same VPN or VPLS. Signaling is the process of establishing pseudo-wires (PW). The PWs constitute the "data plane", whereby PEs send customer VPN/VPLS traffic to other PEs.

With BGP, one has auto-discovery as well as signaling. The mechanisms used are very similar to those used in establishing Layer-3 MPLS VPNs. Each PE is configured to participate in a given VPLS. The PE, through the use of BGP, simultaneously discovers all other PEs in the same VPLS, and establishes a full mesh of pseudo-wires to those PEs. With LDP, each PE router must be configured to participate in a given VPLS, and, in addition, be given the addresses of other PEs participating in the same VPLS. A full mesh of LDP sessions is then established between these PEs. LDP is then used to create an equivalent mesh of PWs between those PEs. An advantage to using PWs as the underlying technology for the data plane is that in case of failure, traffic will automatically be routed along available backup paths in the service provider's network. Failover will be much faster than could be achieved with e.g. Spanning Tree Protocol (STP). VPLS is thus a more reliable solution for linking together Ethernet networks in different locations than simply connecting a WAN link to Ethernet switches in both locations.

VPLS has significant advantages for both service providers and customers. Service providers benefit because they can generate additional revenues by offering a new Ethernet service with flexible bandwidth and sophisticated service level agreements (SLAs). VPLS is also simpler and more cost effective to operate than a traditional service. Customers benefit because they can connect all of their sites to an Ethernet VPN that provides a secure, high speed and homogenous network. Moreover, VPLS provides a logical next step in the continuing evolution of Ethernet from a 10 Mbps shared LAN protocol to a multi-Gbps global service. VPLS MPLS packets have a two-label stack. The outer label is used for normal MPLS forwarding in the service provider's network. If BGP is used to establish the VPLS, the inner label is allocated by a PE as part of a label block. If LDP is used, the inner label is a virtual circuit ID assigned by LDP when it first established a mesh between the participating PEs. Every PE keeps track of assigned inner label, and associates these with the VPLS instance.

PEs participating in a VPLS-based VPN must appear as an Ethernet bridge to connected customer edge (CE) devices. Received Ethernet frames must be treated in such a way as to ensure CEs can be simple Ethernet devices.When a PE receives a frame from a CE, it inspects the frame and learns the CE's MAC address, storing it locally along with LSP routing information. It then checks the frame's destination MAC address. If it is a broadcast frame, or the MAC address is not known to the PE, it floods the frame to all PEs in the mesh. Ethernet does not have a time to live (TTL) field in its frame header, so loop avoidance must be arranged by other means. In regular Ethernet deployments, Spanning Tree Protocol is used for this. In VPLS, loop avoidance is arranged by the following rule: A PE never forwards a frame received from a PE, to another PE. The use of a full mesh combined with split horizon forwarding guarantees a loop-free broadcast domain.VPLS is typically used to link a large number of sites together. Scalability is therefore an important issue that needs addressing.

Split horizon route advertisement

In computer networks, distance-vector routing protocols employ the split horizon route advertisement rule which prohibits a router from advertising a route back out the interface from which it was learned. Split horizon is one of the methods used to prevent routing loops due to the slow convergence times of distance-vector routing protocols.

In this example A uses B to reach C.

A will not advertise its route for C (A to B to C) back to B. On the surface, this seems redundant since B will never use A's route because it costs more than B's route to C. However, if B's route to C goes down, B could end up using A's route, which goes through B; A would send the packet right back to B, creating a loop. With split horizon, this particular loop scenario cannot happen which improves convergence time in complex, highly-redundant environments.

An additional variation of split horizon does advertise the route back to the router that is used to reach the destination, but marks the advertisement as unreachable. This is called split horizon with poison reverse.

With poison reverse, when a routing update indicates that a network is unreachable, routes are immediately removed from the routing table. This breaks erroneous, looping routes before they can propagate through the network. This approach differs from the basic split horizon rule where routes are eliminated through timeouts. Poison reverse has no benefit in networks with no redundancy (single path networks). One disadvantage to poison reverse is that it might significantly increase the size of routing announcements exchanged between neighbors. This is because all routes in the distance vector table are included in each announcement. Although this is generally not an issue on local area networks, it can cause periods of increased utilization on lower-capacity WAN connections.

Protocols using split horizon

• RIP
• IGRP
• EIGRP
• VPLS

Hot Standby Router Protocol

Hot Standby Router Protocol (HSRP) is a Cisco proprietary redundancy protocol for establishing a fault-tolerant default gateway, and has been described in detail in RFC 2281. The Virtual Router Redundancy Protocol (VRRP) is a standards-based alternative to HSRP defined in IETF standard RFC 3768. The two technologies are similar in concept, but not compatible.

The protocol establishes a framework between network routers in order to achieve default gateway failover if the primary gateway should become inaccessible,in close association with a rapid-converging routing protocol like EIGRP or OSPF. By multicasting packets, HSRP sends its hello messages to the multicast address 224.0.0.2 (all routers) using UDP port 1985, to other HSRP-enabled routers, defining priority between the routers. The primary router with the highest configured priority will act as a virtual router with a pre-defined gateway IP and will respond to the ARP request from machines connected to the LAN with the mac address 0000.0c07.acXX where XX is the group ID in hex. If the primary router should fail, the router with the next-highest priority would take over the gateway IP and answer ARP requests with the same mac address, thus achieving transparent default gateway fail-over.HSRP and VRRP are not routing protocols as they do not advertise IP routes or affect the routing table in any way.

HSRP and VRRP on some routers have the ability to trigger a failover if one or more interfaces on the router go down. This can be useful for dual branch routers each with a single serial link back to the head end. If the serial link of the primary router goes down, you would want the backup router to take over the primary functionality and thus retain connectivity to the head end.

Route poisoning

Route poisoning is a method to prevent routing loops within computer networks. Distance-vector routing protocols in computer networks use route poisoning to indicate to other routers that a route is no longer reachable and should be removed from their routing tables. A variation of route poisoning is split horizon with poison reverse whereby a router sends updates with unreachable hop counts back to the sender for every route received to help prevent routing loops. When the protocol detects an invalid route, all of the routers in the network are informed that the bad route has a hop count of 16, which stands for infinity (∞). This makes all nodes on the invalid route seem infinitely distant, resulting in preventing any of the routers from sending packets over the invalid route.

Some distance-vector routing protocols, such as RIP, use a maximum hop count to determine how many routers traffic must go through to reach the destination. Each route has a hop count number assigned to it which is incremented as the routing information is passed from router to router. A route is considered unreachable if the hop count exceeds the maximum allowed. Route poisoning is a method of quickly removing outdated routing information from other router's routing tables by changing its hop count to be unreachable (higher than the maximum number of hops allowed) and sending a routing update. In the case of RIP, the maximum hop count is 15, so to perform route poisoning on a route its hop count is changed to 16, deeming it unreachable, and a routing update is sent. When a router receives a poisoned route, it sends an update back to the router from which it received the poisoned route; this is called poison reverse. This is to ensure that all routers on a segment have received the poisoned route information.

Virtual Routing and Forwarding (VRF)

In IP-based computer networks, Virtual Routing and Forwarding (VRF) is a technology that allows multiple instances of a routing table to co-exist within the same router at the same time. Because the routing instances are independent, the same or overlapping IP addresses can be used without conflicting with each other. Alternative meaning of VRF is a VPN Routing and Forwarding, the key element in the Cisco MPLS VPN technology.A VRF is a routing table instance, that can exist in one instance or multiple instances per each VPN on a Provider Edge (PE) router.VRF may be implemented in a network device by distinct routing tables known as forwarding information bases (FIBs), one per VRF. Alternatively, a network device may have the ability to configure different virtual routers, where each one has its own FIB that is not accessible to any other virtual router instance on the same device.

The simplest form of VRF implementation is VRF Lite. In this implementation, each router within the network participates in the virtual routing environment in a peer-based fashion. While simple to deploy and appropriate for small to medium enterprises and shared data centres, VRF Lite does not scale to the size required by global enterprises or large carriers, as there is the need to implement each VRF instance on every router. The scaling limitations of VRF Lite are resolved by the implementation of IPVPNs. In this implementation, a core backbone network is responsible for the transmission of data across the wide area between VRF instances at each edge location. IPVPNs have been traditionally deployed by carriers to provide a shared wide-area backbone network for multiple customers. They are also appropriate in large enterprise, multi-tenant and shared data centre environments.

In a typical deployment, Customer Edge (CE) routers handle local routing in a traditional fashion and disseminate routing information into Provider Edge (PE) where the routing tables are virtualised. The PE router then encapsulates the traffic, marks it to identify the VRF instance, and transmits it across the provider backbone network to the destination PE router. The destination PE router then un-encapsulates the traffic and forwards it to the CE router at the destination. The backbone network is completely transparent to the customer equipment, allowing multiple customers or user communities to utilize the common backbone network while maintaining end-to-end traffic separation.Routes across the provider backbone network are maintained using an Interior Gateway Protocol - typically iBGP. iBGP uses extended community attributes in a common routing table to differentiate the customers' routes with overlapping IP addresses. IPVPN is most commonly deployed across a Multi-protocol Label Switching (MPLS) backbone as the inherent labelling of packets in MPLS lends itself to the identification of the customer VRF. Some IPVPN implementations (notably Nortel's IP-VPN Lite) utilize a simpler IP-in-IP encapsulation over a pure IP backbone, eliminating the need to maintain and support an MPLS environment.

Generic Routing Encapsulation

GRE or Generic Routing Encapsulation - it is a tunneling protocol that was originally developed by Cisco for encapsulation of arbitrary kinds of network layer packets inside arbitrary kinds of network layer packets. This is brief tutorial on creating a GRE tunnel between two Cisco routes. Suppose that we have two sites; SiteA and SiteB. SiteA's router has interface Eth0 with the following IP address 10.0.1.1/24 and secondary IP address 1.0.1.1/24. Where the users (LAN) are connected to 10.0.1.0/24 subnet. The router has serial interface connected to the Internet (ISP). Same for SiteB, it has Eth0 with IP address 10.0.2.1/24 and secondary IP 1.0.2.1/24 where the users (LAN) are connected to 10.0.1.0/24 subnet. The router has serial interface connected to the Internet (ISP). Now we want to create a GRE tunnel in order for 10.0.1.0/24 and 10.0.2.0/24 subnets to communicate with each other.

Cisco Discovery Protocol

The Cisco Discovery Protocol (CDP) is a proprietary layer 2 network protocol developed by Cisco Systems that runs on most Cisco equipment and is used to share information about other directly connected Cisco equipment such as the operating system version and IP address. CDP can also be used for On-Demand Routing (ODR), which is a method of including routing information in CDP announcements so that dynamic routing protocols do not need to be used in simple networks.

Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc (also used for other Cisco proprietary protocols such as VTP). CDP announcements (if supported and configured in IOS) are sent by default every 60 seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers, including Ethernet, Frame Relay and ATM. Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. The CDP table's information is refreshed each time an announcement is received, and the holdtime for that entry is reset. The holdtime specifies how long an entry in the table will be kept - if no announcements are received from a device and the holdtime timer expires for that entry, the device's information is discarded (default 180 seconds).

The information contained in CDP announcements varies by the type of device and the version of the operating system running on it. Information contained includes the operating system version, hostname, every address for every protocol configured on the port where CDP frame is sent eg. IP address, the port identifier from which the announcement was sent, device type and model, duplex setting, VTP domain, native VLAN, power draw (for Power over Ethernet devices), and other device specific information. The details contained in these announcements is easily extended due to the use of the type-length-value (TLV) frame format. See external links for a technical definition. HP removed support for sending CDP from HP Procurve products shipping after February 2006 and all future software upgrades. Receiving CDP and showing neighbor information is still supported. CDP support was replaced with Link Layer Discovery Protocol.

Netflow

NetFlow is a network protocol developed by Cisco Systems to run on Cisco IOS-enabled equipment for collecting IP traffic information. It is proprietary and supported by platforms other than IOS, such as Juniper routers, Linux or FreeBSD and OpenBSD.

Cisco routers that have the Netflow feature enabled generate netflow records; these are exported from the router in User Datagram Protocol (UDP) or Stream Control Transmission Protocol (SCTP) packets and collected using a netflow collector. Other vendors provide similar features for their routers but with different names:

Jflow or cflowd for Juniper Networks
NetStream for 3Com/H3C
NetStream for Huawei Technology
Cflowd for Alcatel-Lucent

network flow has been defined in many ways. The traditional Cisco definition is to use a 7-tuple key, where a flow is defined as a unidirectional sequence of packets all sharing all of the following 7 values:

1. Source IP address
2. Destination IP address
3. Source port for UDP or TCP, 0 for other protocols
4. Destination port for UDP or TCP, type and code for ICMP, or 0 for other protocols
5. IP protocol
6. Ingress interface (SNMP ifIndex)
7. IP Type of Service

Flexible Netflow and IPFIX support user-defined flow keys. The router will output a flow record when it determines that the flow is finished. It does this by flow aging: when the router sees new traffic for an existing flow it resets the aging counter. Also, TCP session termination in a TCP flow causes the router to expire the flow. Routers can also be configured to output a flow record at a fixed interval even if the flow is still ongoing. In Flexible NetFlow (FNF) an administrator could actually define flow properties on the router.

Ingress router

An ingress router is a Label Switch Router that is a starting point (source) for a given Label Switched Path. An ingress router may be an egress router or an intermediate router for any other LSP(s). Hence the role of ingress and egress routers is LSP specific. Usually, the MPLS label is attached with an IP packet at the ingress router and removed at the egress router, whereas label swapping is performed on the intermediate routers. However, in special cases (such as LSP Hierarchy in RFC 4206, LSP Stitching [1] and MPLS local protection) the ingress router could be pushing label in label stack of an already existing MPLS packet (instead of an IP packet). Note that, although the ingress router is the starting point of an LSP, it may or may not be the source of the under-lying IP packets.

Label switch router

A Label Switch Router (LSR) (sometimes called transit router), is a type of a router located in the middle of a Multiprotocol Label Switching (MPLS) network. It is responsible for switching the labels used to route packets. When an LSR receives a packet, it uses the label included in the packet header as an index to determine the next hop on the Label Switched Path (LSP) and a corresponding label for the packet from a look-up table. The old label is then removed from the header and replaced with the new label before the packet is routed forward.

Label Switched Path

In MPLS networking, a Label Switched Path (LSP) is a path through an MPLS network, set up by a signaling protocol such as LDP, RSVP-TE, BGP or CR-LDP.The path begins at a Label Edge Router (LER), which makes a decision on which label to prefix to a packet based on the appropriate FEC. It then forwards the packet along to the next router in the path, which swaps the packet's outer label for another label, and forwards it to the next router. The last router in the path removes the label from the packet and forwards the packet based on the header of its next layer, for example IPv4. Due to the forwarding of packets through an LSP being opaque to higher network layers, an LSP is also sometimes referred to as an MPLS tunnel.

The router which first prefixes the MPLS header to a packet is called an ingress router. The last router in an LSP, which pops the label from the packet, is called an egress router. Routers in between, which need only swap labels, are called transit routers or Label Switching Router (LSR)s.Note that LSPs are unidirectional; they enable a packet to be label switched through the MPLS network from one endpoint to another. Since bidirectional communication is typically desired, the aforementioned dynamic signaling protocols can set up an LSP in the other direction to compensate for this. When protection is considered, LSPs could be categorized as primary(working), secondary(backup) and tertiary (LSP of last resort). As described above, LSPs are normally P2P (Point to Point). A new concept of LSPs, which are known as P2MP (Point to Multi Point), was introduced recently. These are mainly used for multicasting purposes.