# Weird Junos IS-IS Metrics

DevFeed: [Weird Junos IS-IS Metrics](<https://devfeed.tech/articles/weird-junos-is-is-metrics-11122.md>)

Original publisher: [Read original article](<https://blog.ipspace.net/2025/01/junos-isis-metrics/>)

Published: 2025-01-14T07:13:00Z

Content type: opinion

Language: en

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

Topics: [IS-IS](<https://devfeed.tech/topics/is-is.md>), [networking](<https://devfeed.tech/topics/networking.md>), [Routing (disambiguation)](<https://devfeed.tech/topics/routing.md>), [Development](<https://devfeed.tech/topics/development.md>)

Tags: [development-process](<https://devfeed.tech/tags/development-process.md>), [is-is](<https://devfeed.tech/tags/is-is.md>), [netlab](<https://devfeed.tech/tags/netlab.md>), [router](<https://devfeed.tech/tags/router.md>), [routing](<https://devfeed.tech/tags/routing.md>), [tests](<https://devfeed.tech/tags/tests.md>), [validation](<https://devfeed.tech/tags/validation.md>)

## AI overview

The article investigates a failing netlab IS-IS metrics test on Junos. It explains that Junos uses transitional IS-IS metrics by default and silently limits configured narrow and wide metrics above 63, causing unexpected routing costs. Configuring wide-metrics-only on levels 1 and 2 resolves the test failure.

## Source excerpt

As part of the netlab development process, I run almost 200 integration tests on more than 20 platforms (over a dozen operating systems), and the amount of weirdness I discover is unbelievable. Today's special: Junos is failing the IS-IS metrics test. The test is trivial: The device under test is connected to two IS-IS routers (X1 and X2) It has a low metric configured on the link with X1 and a high metric configured on the link with X2 The validation process is equally trivial: Read more ...