FAQ.md
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@@ -54,6 +54,22 @@ We used to assign ASN in the 64600-64855 range, where you would get ASN 64600+X
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Prior to using ASNs in the new private ASN range 4200000000-4294967294 ([RFC6996](http://tools.ietf.org/html/rfc6996)) Some ASNs were allocated from the [ASN reserved block](http://www.iana.org/assignments/as-numbers/as-numbers.xhtml) in the 76100-76199 range.
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+### Why can't my Docker containers connect to other DN42 hosts?
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+
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+By default, Docker overlaps with the entire DN42 range and then some. (172.16.0.0/12 == 172.16.0.0 - 172.31.255.255)
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+
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+In order to prevent this, you need to supply a different subnet range to the Docker daemon. This can be done by creating or updating `/etc/docker/daemon.json` with something along the following (this will use 192.168.128.0/18 == 192.168.128.0 - 192.168.128.0 - 192.168.191.255)
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+```json
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+{
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+ "default-address-pools" : [
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+ {
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+ "base" : "192.168.128.0/18",
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+ "size" : 24
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+ }
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+ ]
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+}
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+```
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+Note, I (@bri / AS4242422825) have only tested this with Docker version 23.0.0, build e92dd87. But it should work with any current version. I don't know how Swarm etc. networking works, this might need additional tweaking for other versions. (Referenced from https://straz.to/2021-09-08-docker-address-pools/ and https://docs.docker.com/network/bridge/ — I used this to get my `thelounge` container to connect to hackint.dn42.)
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### Can I update the wiki?
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