Introduction to OSPF

Lessons Discussion
202

Thank you @lagapidis for your swift response as usal, they are connected over the carrier circuit. In carrier (transmission), their MTU is 12323.

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203

Hi
I am confused.
I have configured Ospf network type p2p on R1 and the adjacent router R2 default network type Broadcast.
so I have a network type mismatch
I thought this would cause the routers to fail establishing a full adjacency, however, they form a full adjacency regardless of the network type mismatch.
is this a fix in IOS XE or has this always been the case?
I think I was taught that the network type must match in order to establish a full adjacency?

204

Hello Orla

I understand your confusion. You should indeed configure the same network types on adjacent OSPF routers, but there are cases where an adjacency will still form if the network type is different. You can find out more details about this at the NetworkLessons note titled: OSPF Network Type Mismatch.

Even if an adjacency may form if the network type is different you should always ensure that you have the same network type on both ends for any production network!

I hope this has been helpful!

Laz

205

The RIP Load-balancing, was based on Source/Destination Traffic Flow with IP Hashing. right?

Does OSPF also load-balance in that way, or is that 50:50 per packet sharing?

206

Hello Pamod

OSPF uses exactly the same load balancing method as RIP. Both protocols use per-destination load balancing with source/destination IP hashing by default, not 50/50 per-packet sharing.

This is because load balancing is not a function of the routing protocol itself. The routing protocol, whether RIP, OSPF, or EIGRP, simply tells the router that there are multiple equal-cost paths. Once that is established, the load balancing is handled by the forwarding plane function of the router. In most modern Cisco devices, this is performed by CEF (Cisco Express Forwarding).

The routing protocol operates on the control plane, while CEF, which does the actual forwarding of user data, operates on the data plane. Make sense?

I hope this has been helpful!

Laz