# OSPF Summarization and Split Areas

DevFeed: [OSPF Summarization and Split Areas](<https://devfeed.tech/articles/ospf-summarization-and-split-areas-10968.md>)

Original publisher: [Read original article](<https://blog.ipspace.net/2024/03/ospf-split-areas-summarization/>)

Published: 2024-03-12T06:39:00Z

Content type: tutorial

Language: en

Sources: [ipSpace.net blog](<https://devfeed.tech/sources/ipspace-net-blog.md>)

Topics: [networking](<https://devfeed.tech/topics/networking.md>), [Routing (disambiguation)](<https://devfeed.tech/topics/routing.md>), [Protocol (disambiguation)](<https://devfeed.tech/topics/protocol.md>)

Tags: [gre](<https://devfeed.tech/tags/gre.md>), [network](<https://devfeed.tech/tags/network.md>), [ospf](<https://devfeed.tech/tags/ospf.md>), [protocol](<https://devfeed.tech/tags/protocol.md>), [route](<https://devfeed.tech/tags/route.md>), [routing](<https://devfeed.tech/tags/routing.md>)

## AI overview

This tutorial explains how OSPF inter-area route summarization can cause traffic black holes when an area is split into disconnected fragments. It examines the failure scenario and describes disabling summarization or connecting the fragments with a GRE tunnel as possible fixes, while noting that virtual links do not solve this case.

## Source excerpt

In the Do We Still Need OSPF Areas and Summarization? I wrote this somewhat cryptic remark: The routers advertising a summarized prefix should be connected by a path going exclusively through the part of the network with more specific prefixes. GRE tunnel also satisfies that criteria; the proof is left as an exercise for the reader. One of my readers asked for a lengthier explanation, so here we go. Imagine a network with two areas doing inter-area summarization on /24 boundary: Read more ...