Quick Answer: What Layer Is OSPF?

Is OSPF Classful or classless?

Classful routing protocols do not carry subnet masks; classless routing protocols do.

Older routing protocols, including RIP and IGRP, are classful.

Newer protocols, including RIP-2, EIGRP, and OSPF, are classless..

Is Rip a TCP or UDP?

RIP uses the User Datagram Protocol (UDP) as its transport protocol, and is assigned the reserved port number 520.

What is ip classless?

At times the router might receive packets destined for a subnet of a network that has no network default route. To have the Cisco IOS software forward such packets to the best supernet route possible, use the ip classless global configuration command.

How does OSPF choose best path?

If there are multiple routes to a network with the same route type, the OSPF metric calculated as cost based on the bandwidth is used for selecting the best route. The route with the lowest value for cost is chosen as the best route.

Why We Use Area in OSPF?

OSPF uses areas to simplify administration and optimize traffic and resource utilization. An area is simply a logical grouping of contiguous networks and routers. All routers in the same area have the same topology table and don’t know about routers in the other areas.

Who invented OSPF?

Internet Engineering Task ForceOSPF is developed by Internet Engineering Task Force (IETF) as one of the Interior Gateway Protocol (IGP), i.e, the protocol which aims at moving the packet within a large autonomous system or routing domain. It is a network layer protocol which works on the protocol number 89 and uses AD value 110.

What is router OSPF 1?

I need to use the router ospf command to get into the OSPF configuration. The number “1” is a process ID and you can choose any number you like. It doesn’t matter and if you want you can use a different number on each router.

Where is OSPF used?

The OSPF (Open Shortest Path First) protocol is one of a family of IP Routing protocols, and is an Interior Gateway Protocol (IGP) for the Internet, used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network.

Does OSPF use hop count?

Distance-vector metrics RIP always uses the lowest hop count, regardless of the speed or reliability of a link. OSPF is a link-state protocol, which means that OSPF can take into account a variety of link conditions, such as the reliability or speed of the link, when determining the best path to a destination network.

Is BGP Layer 3 or 4?

For the most part, routing is a layer-3 function, but, as you pointed out, BGP uses a layer-4 protocol to communicate with other BGP speakers in order to do what is normally considered a layer-3 function. Many network protocols fall into a gray area, or are considered in one layer while using another layer.

Is BGP classless?

RIP-1 and IGRP are grouped under classful protocols, whereas the more recently developed RIP-2, EIGRP, OSPF, IS-IS, and BGP fall in the classless category. The Exterior Gateway Protocol (EGP), the predecessor of the Border Gateway Protocol (BGP), which currently is considered obsolete, is also a classful protocol.

Why OSPF is faster than RIP?

OSPF allows a router to build a shortest path tree with a router as the root. Because the link-state information provides richer information than does this in vector, OSPF typically converges faster than RIP when there is a failure in the network.

What does BGP stand for?

Border Gateway Protocol“Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information between autonomous systems (AS) on the Internet.


OSPF Packets Because OSPF does not use UDP or TCP, the OSPF protocol is fairly elaborate and must reproduce many of the features of a transport protocol to move OSPF messages between routers. There can be one of five OSPF packet types inside the IP packet, all of which share a common OSPF header.

What is OSPF metric?

The OSPF metric for a route is the sum of the interface costs for all outgoing interfaces in the route. By default, a router’s OSPF interface cost is actually derived from the interface bandwidth: The faster the bandwidth, the lower the cost.

How do I enable OSPF?

To enable OSPF on a Cisco router and advertise interfaces, the following tasks are required:Use the command router ospf process ID to start OSPF.Use the network command to enable the interfaces.Identify area assignments.(Optional) Assign the router ID.

Is OSPF open standard?

The Open Shortest Path First (OSPF) protocol is a link state protocol that handles routing for IP traffic. Its newest implementation, version 2, which is explained in RFC 2328, is an open standard. Open Shortest Path First (OSPF) is an open standard (not proprietary) and it will run on most routers independent of make.

What is IP OSPF cost?

Use the ip ospf cost command to configure the cost metric manually for each interface. This command overrides any settings for the reference bandwidth that you set using the reference-bandwidth command in router configuration mode.

How is OSPF calculated?

Open Shortest Path First (OSPF) uses “Cost” as the value of metric and uses a Reference Bandwidth of 100 Mbps for cost calculation. The formula to calculate the cost is Reference Bandwidth divided by interface bandwidth. For example, in the case of 10 Mbps Ethernet , OSPF Metric Cost value is 100 Mbps / 10 Mbps = 10.

Is OSPF proprietary?

OSPF (Open Shortest Path First) is perhaps the most popular link state routing protocol. It is an open standard so it can be run on routers produced by different vendors, which is in contrast to EIGRP, a Cisco proprietary protocol that can be run only on Cisco devices. … OSPF uses the multicast addresses of 224.0.

Is OSPF distance vector?

OSPF is not a distance-vector protocol like RIP, but a link-state protocol with a set of metrics that can be used to reflect much more about a network than just the number of routers encountered between source and destination. In OSPF, a router attempts to route based on the “state of the links.”