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DEMO: Configure Ethernet as a Point-to-Point

When only two OSPF-enabled devices share an Ethernet segment, configuring the interface as a point-to-point network type eliminates the unnecessary Designated Router and Backup Designated Router election process, reducing overhead on the link.

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About this video

OSPF handles multi-access networks, such as Ethernet segments, by electing a Designated Router (DR) and Backup Designated Router (BDR) to reduce the volume of routing updates exchanged among neighbors. This mechanism is essential when many devices share the same segment, but it introduces unnecessary complexity and overhead when only two devices are connected, since OSPF still treats the Ethernet interface as a potential multi-access environment and proceeds with the election regardless. To address this, the OSPF network type on the relevant interfaces can be manually overridden. Entering interface configuration mode on each device and issuing the ip ospf network point-to-point command instructs OSPF to treat the link as a direct connection between two peers, skipping the DR and BDR election entirely. This change must be applied consistently on both sides of the link to ensure proper adjacency formation. Once configured, verification commands such as show ip ospf interface and show ip ospf neighbor confirm that the DR and BDR roles are no longer present and that the interface state has transitioned to point-to-point. The result is a leaner, more efficient OSPF adjacency on links where the multi-access election process serves no practical purpose.

What you'll learn

What's covered

OSPF Point-to-Point Network Type

Aligned to

Cisco CCNA
3.4 Configure and verify single area OSPFv2

Key terms

Router
A network device that forwards data packets between networks based on IP addresses.
Routing Protocol
A protocol used by routers to communicate and share routing information to determine the best path for data.
Open Shortest Path First
OSPF
A link-state interior gateway routing protocol that maintains a complete map of the network topology and uses Dijkstra's Shortest Path First algorithm to calculate optimal, loop-free routes. OSPF divides networks into hierarchical areas to improve scalability and supports VLSM and rapid convergence.
Disaster Recovery
DR
The process and procedures for recovering IT systems and data following a disruptive event.
Backup Designated Router
BDR
An OSPF router elected on a multi-access network segment as the backup to the Designated Router, ready to take over DR functions if the DR fails. The BDR maintains adjacencies with all other routers on the segment to minimize reconvergence time.
Multi-Access Network
A network type, such as Ethernet, where multiple devices share the same Layer 2 medium and can potentially communicate with one another.
Point-to-Point Network
An OSPF network type configured between exactly two routers that eliminates the need for DR and BDR elections, reducing unnecessary overhead.

Transcript

When we have multi-access networks, and they become very large, it can get really chatty, and so we need to elect a designated router and a backup designated router. However, there are times when we just have two devices on that link and we really don't need to elect a designated router and a backup designated router, since there's just two devices. Although it still thinks that there could be more, since it's an Ethernet, since it's a multi-access network, and so it's going to still treat it as a designated router and backup designated router, as a multi-access network.

What we can do is we can actually go into our interfaces that are part of our Ethernet connections and specify that this is actually a point-to-point connection that you're making here, that it's not a multi-access network.

The network

Here we have all of these layer 3 devices speaking OSPF. OSPF is what's communicating all of the networks to each other. These two are point-to-point protocols and they don't go through the election process, but between this router and this layer 3 switch, this is an Ethernet, this is a multi-access network, and this router doesn't realize there's only one other device on there.

So what we're going to do is we're going to get onto both of these, router 1 and switch 1, and define this as being just a point-to-point network.

Making the change

I'm going to jump onto router 1 and I'm going to do a show ip ospf interface, and we are looking at fa01. I'm going to pull this up, and it says that it's elected a backup designated router and it's got the information for this. I could also do a show ip ospf neighbor, and we can see here too that this is a DR that's elected.

So what I'm going to do is I'm going to get into the global configuration mode, and within this interface I'm going to type in the command ip ospf network point-to-point and hit enter there. And I'm going to do the same thing to make it consistent on the other side, which is VLAN 9 is what this is connected to. So I've just did it there.

Now I can pull this back up, and we're going to end out of here. I'll do my other commands and we'll see if this is actually updated, and we can see that it no longer has that DR, backup designated router relationship there. So I hit enter, and sure enough it is no longer on our connections. We do the show ip ospf neighbor, we don't see it there. And then we take a look at the interface, and same thing on the interface, the state is point to point.

So that's one way that we can change it so that there'd be less chatty on this network.

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