# CIS Ubuntu 14.04 LTS - 3.3.2 Ensure IPv6 redirects are not accepted

> Verify that IPv6 ICMP redirects are not accepted to prevent routing to compromised machines

- Skill: `cyberstrikeus/cis-ubuntu-14-04-lts-3-3-2-ensure-ipv6-redirects-are-not-acc` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/cis-ubuntu-14-04-lts-3-3-2-ensure-ipv6-redirects-are-not-acc`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/cis-ubuntu-14-04-lts-3-3-2-ensure-ipv6-redirects-are-not-acc/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/cis-ubuntu-14-04-lts-3-3-2-ensure-ipv6-redirects-are-not-acc

---


# 3.3.2 Ensure IPv6 redirects are not accepted (Not Scored)

## Profile Applicability

- Level 1 - Server
- Level 1 - Workstation

## Description

This setting prevents the system from accepting ICMP redirects. ICMP redirects tell the system about alternate routes for sending traffic.

## Rationale

It is recommended that systems not accept ICMP redirects as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes.

## Audit Procedure

Run the following commands and verify output matches:

```bash
sysctl net.ipv6.conf.all.accept_redirects
# Expected: net.ipv6.conf.all.accept_redirect = 0

sysctl net.ipv6.conf.default.accept_redirects
# Expected: net.ipv6.conf.default.accept_redirect = 0

grep "net\.ipv6\.conf\.all\.accept_redirect" /etc/sysctl.conf /etc/sysctl.d/*
# Expected: net.ipv6.conf.all.accept_redirect = 0

grep "net\.ipv6\.conf\.default\.accept_redirect" /etc/sysctl.conf /etc/sysctl.d/*
# Expected: net.ipv6.conf.default.accept_redirect = 0
```

## Expected Result

```
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
```

## Remediation

Set the following parameters in `/etc/sysctl.conf` or a `/etc/sysctl.d/*` file:

```
net.ipv6.conf.all.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0
```

Run the following commands to set the active kernel parameters:

```bash
sysctl -w net.ipv6.conf.all.accept_redirects=0
sysctl -w net.ipv6.conf.default.accept_redirects=0
sysctl -w net.ipv6.route.flush=1
```

## Default Value

Not specified.

## References

- CIS Controls: 3 - Secure Configurations for Hardware and Software on Mobile Devices, Laptops, Workstations, and Servers
- CIS Controls: 11 - Secure Configurations for Network Devices such as Firewalls, Routers and switches

## Profile

- Level 1 - Server
- Level 1 - Workstation