69 lines
1.8 KiB
Markdown
69 lines
1.8 KiB
Markdown
title: Announcing IPv6 networks without becoming the default router
|
||
---
|
||
pub_date: 2020-01-31
|
||
---
|
||
author: ungleich network team
|
||
---
|
||
twitter_handle: ungleich
|
||
---
|
||
_hidden: no
|
||
---
|
||
_discoverable: yes
|
||
---
|
||
abstract:
|
||
You can also announce prefixes without becoming the default router
|
||
---
|
||
body:
|
||
|
||
## TL;DR
|
||
|
||
Use **AdvDefaultLifetime 0** in your radvd.conf if you don't want the
|
||
router to become a default router.
|
||
|
||
## Background
|
||
|
||
Sometimes you have multiple routers in a network and you don't want a
|
||
router to become the default router for clients, but it should still
|
||
announce an IPv6 prefix.
|
||
|
||
## radvd
|
||
|
||
Luckily radvd supports an option to notify the clients of this. From the manpage of radvd.conf(5):
|
||
|
||
|
||
```
|
||
AdvDefaultLifetime seconds
|
||
|
||
The lifetime associated with the default router in units of seconds. The
|
||
maximum value corresponds to 18.2 hours. A lifetime of 0 indicates that
|
||
the router is not a default router and should not appear on the default
|
||
router list. The router lifetime applies only to the router's usefulness
|
||
as a default router; it does not apply to information contained in other
|
||
message fields or options. Options that need time limits for their infor‐
|
||
mation include their own lifetime fields.
|
||
|
||
Must be either zero or between MaxRtrAdvInterval and 9000 seconds.
|
||
|
||
Default: 3 * MaxRtrAdvInterval (Minimum 1 second).
|
||
|
||
```
|
||
|
||
## Sample configuration
|
||
|
||
A configuration from one of our test sites looks as follows:
|
||
|
||
```
|
||
interface eth0
|
||
{
|
||
AdvSendAdvert on;
|
||
MinRtrAdvInterval 3;
|
||
MaxRtrAdvInterval 5;
|
||
|
||
AdvDefaultLifetime 0;
|
||
|
||
prefix 2a0a:e5c1:111:10c::/64 { };
|
||
};
|
||
```
|
||
|
||
Client in this test network assign themselves an additional IPv6
|
||
address from this prefix.
|