# Lab: Distributing Level-2 IS-IS Routes into Level-1 Areas

DevFeed: [Lab: Distributing Level-2 IS-IS Routes into Level-1 Areas](<https://devfeed.tech/articles/lab-distributing-level-2-is-is-routes-into-level-1-areas-11310.md>)

Original publisher: [Read original article](<https://blog.ipspace.net/2026/01/isis-inter-area-routes/>)

Published: 2026-01-21T07:06:00Z

Content type: tutorial

Language: en

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

Topics: [IS-IS](<https://devfeed.tech/topics/is-is.md>), [GitHub](<https://devfeed.tech/topics/github.md>)

Tags: [browser](<https://devfeed.tech/tags/browser.md>), [github](<https://devfeed.tech/tags/github.md>), [infrastructure](<https://devfeed.tech/tags/infrastructure.md>), [is-is](<https://devfeed.tech/tags/is-is.md>), [netlab](<https://devfeed.tech/tags/netlab.md>), [ospf](<https://devfeed.tech/tags/ospf.md>), [route](<https://devfeed.tech/tags/route.md>)

## AI overview

This lab explains how IS-IS handles inter-area routes differently from OSPF. It explores distributing level-2 IS-IS routes into level-1 areas, including the default behavior and its consequences.

## Source excerpt

One of the major differences between OSPF and IS-IS is their handling of inter-area routes. Non-backbone OSPF intra-area routes are copied into the backbone area and later (after the backbone SPF run) copied into other areas. IS-IS does not copy level-2 routes into level-1 areas; level-1 areas (by default) behave like totally stubby OSPF areas with the level-1 routers using the Attached (ATT) bit of level-1-2 routers in the same area to generate the default route. Read more ...