Bug 1477365 - Fedora-25 HOST + CentOS-6 GUESTS Linux/LXC: Guests can't connect to each other or to default router ...
Fedora-25 HOST + CentOS-6 GUESTS Linux/LXC: Guests can't connect to each othe...
Product: Fedora
Classification: Fedora
Component: lxc (Show other bugs)
x86_64 Linux
unspecified Severity high
: ---
: ---
Assigned To: Thomas Moschny
Fedora Extras Quality Assurance
Depends On:
  Show dependency treegraph
Reported: 2017-08-01 17:48 EDT by prismalytics
Modified: 2017-12-12 05:19 EST (History)
5 users (show)

See Also:
Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2017-12-12 05:19:06 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
Command output from the Fedora-25 HOST (12.12 KB, text/plain)
2017-08-01 17:48 EDT, prismalytics
no flags Details
Command output from a CentOS-6.9 Final GUEST (2.21 KB, text/plain)
2017-08-01 17:50 EDT, prismalytics
no flags Details

  None (edit)
Description prismalytics 2017-08-01 17:48:54 EDT
Created attachment 1307821 [details]
Command output from the Fedora-25 HOST

Hello Friends:

I'm not sure if this is a bug, but here is my sudden issue.

The Linux/LXC single-box cluster setup:
1) I use Fedora x86_64 (currently Fedora-25) as the LXC/HOST O/S.
   I use CentOS-6 x86_64 (currently CentOS-6.9 Final) for the six (qty. 6) LXC/GUEST O/S'.

2) This was working for a long time (a few years), but suddenly does not after a
   'sudo dnf -y update' (HOST) and 'sudo yum -y update' (GUESTS).

   It has been a few months since I booted this HOST/GUESTS LXC "cluster" and, as
   usual, O/S updates are the first thing that I perform. This may provide a hint if
   some underlying system-level component(s)/behavior(s) changed during that time.

3) The Fedora HOST and CentOS-6 GUESTS are on the same subnet, and share the same
   default router:; (all standard stuff).

4) The Fedora Host does not have any firewall/firewalld RPM packages installed, and
   therefore doesn't not run a firewall. I removed this long ago to simplify things.

The issue
1) After performing the above O/S updates to the HOST and GUESTS, from within any
   GUEST, I can no longer (a) successfully ping/ssh guest-to-guest or (b) ping the
   default router.

2) I can, however, ping/ssh HOST-to-GUEST and GUEST-to-HOST with no issue.

3) From any computer outside this setup -- which, by the way, are also on the same
   subnet and share the same default router as above -- I can ping/ssh to the
   HOST but cannot to any of the GUESTS.

3) Other than performing the aforementioned O/S updates, I didn't alter anything.

Some output
I attached some command output to this submission. Note that the GUESTS are named
vps00, vps01, vps02, vps03, vps04 and vps10. While the HOST is named lxc-host.
Throughout the attachment, you'll see some notes that I annotated it with.

Any ideas? Thank you in advance.
Comment 1 prismalytics 2017-08-01 17:50 EDT
Created attachment 1307822 [details]
Command output from a CentOS-6.9 Final GUEST
Comment 2 prismalytics 2017-08-01 17:55:36 EDT
P.S. There are two attachments (with some annotations within them):

   - HOST.txt
   - ONE_GUEST.txt

Thank you! :)
Comment 3 prismalytics 2017-08-02 20:05:21 EDT

Thanks to the accepted answer in this POST https://unix.stackexchange.com/questions/125599/settings-when-using-a-bridge, I was able to finally figure out the iptables(1M) entries that were missing. 

Here they are:

    sudo iptables -A INPUT -i eth0 -j ACCEPT
    sudo iptables -A INPUT -i br0 -j ACCEPT
    sudo iptables -A FORWARD -i br0 -j ACCEPT

I don't know what Fedora HOST O/S changes occurred to make these entries not be there suddenly (meaning after doing "dnf -y update; reboot" after a few months of not doing that), but would sure love to know because now I have to hardcode these entries in somewhere (which I'm not thrilled about). :)

Any insight from friends here would be appreciated because maybe I can avoid doing that with some guidance (thanks).

I hope this helps others who bridge their LXC guests like I do.
Comment 4 Fedora End Of Life 2017-11-16 13:32:06 EST
This message is a reminder that Fedora 25 is nearing its end of life.
Approximately 4 (four) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 25. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as EOL if it remains open with a Fedora  'version'
of '25'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version'
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not
able to fix it before Fedora 25 is end of life. If you would still like
to see this bug fixed and are able to reproduce it against a later version
of Fedora, you are encouraged  change the 'version' to a later Fedora
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's
lifetime, sometimes those efforts are overtaken by events. Often a
more recent Fedora release includes newer upstream software that fixes
bugs or makes them obsolete.
Comment 5 Fedora End Of Life 2017-12-12 05:19:06 EST
Fedora 25 changed to end-of-life (EOL) status on 2017-12-12. Fedora 25 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this

Thank you for reporting this bug and we are sorry it could not be fixed.

Note You need to log in before you can comment on or make changes to this bug.