Multiple Interfaces, Not Seeing Requests

[Adam Bishop]

On 6 Feb 2017, at 22:38, Matthew West <matthew.t.west at gmail.com> wrote:
> I'm happy to do the legwork for this one.  Can someone point me in the
> right direction for further troubleshooting?

RHEL/CentOS does not work well with multiple interfaces out of the box for some network configurations. You need to enable a few kernel settings to make it do the right thing.

It sounds like you may have one of the affected configurations.

The issue is detailed here:
  https://access.redhat.com/solutions/53031

You can confirm this by enabling martian logging using sysctl:
  net.ipv4.conf.*.log_martians=1

I wouldn't enable martial logging permanently; it's not necessary in normal operation and could cause your logging process  (rysslog/journald) to start discarding useful traffic.

Note that in my experience, setting default/all is not sufficient; you need to apply it to each individual interface explicitly. This may have changed in 7.3, or may not be the case if you're using an interface naming scheme that doesn't start with 'eno'.

If you're using firewalld, you also need to make sure that auxiliary interfaces are assigned to the correct zone.

Regards,

Adam Bishop

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