network: add note for possible fix/workaround in NAT setup

apparently sometimes users have problems reaching outside internet with
some network setups. this is the workaround a user suggested that
we should add in the wiki.

Signed-off-by: Oguz Bektas <o.bektas@proxmox.com>
This commit is contained in:
Oguz Bektas 2020-02-10 16:06:11 +01:00 committed by Thomas Lamprecht
parent 8dc994f7f4
commit 22d5244018

View File

@ -248,6 +248,24 @@ iface vmbr0 inet static
post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o eno1 -j MASQUERADE post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o eno1 -j MASQUERADE
---- ----
NOTE: In some masquerade setups with firewall enabled, conntrack zones might be
needed for outgoing connections. Otherwise the firewall could block outgoing
connections since they will prefer the `POSTROUTING` of the VM bridge (and not
`MASQUERADE`).
Adding these lines in the `/etc/network/interfaces` can fix this problem:
----
post-up iptables -t raw -I PREROUTING -i fwbr+ -j CT --zone 1
post-down iptables -t raw -D PREROUTING -i fwbr+ -j CT --zone 1
----
For more information about this, refer to the following links:
https://commons.wikimedia.org/wiki/File:Netfilter-packet-flow.svg[Netfilter Packet Flow]
https://lwn.net/Articles/370152/[Patch on netdev-list introducing conntrack zones]
https://blog.lobraun.de/2019/05/19/prox/[Blog post with a good explanation by using TRACE in the raw table]
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