Add older dhcrelay syntax to "Deploying Overcloud with L3 routed networking"

[Ian Pilcher]

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-----------------------------------
Release: 0.0.1.dev800 on 2018-05-31 00:25
SHA: b80ce896a20fa5ffcd800f500ee8bd9c012d0396
Source: https://git.openstack.org/cgit/openstack/tripleo-docs/tree/doc/source/install/advanced_deployment/routed_spine_leaf_network.rst
URL: https://docs.openstack.org/tripleo-docs/latest/install/advanced_deployment/routed_spine_leaf_network.html

It seems that dhcrelay's command-line options have changed recently. The syntax in the "DHCP relay configuration (Example)" section works for more recent versions (4.3.6 in Fedora, for example), but it doesn't work with the version in CentOS 7 (4.2.5).

AFAICT, the equivalent syntax for the older version version would be:

   dhcrelay -d -i eth1 -i eth2 -i eth3 172.20.0.10 172.20.0.1

[Ian Pilcher (arequipeno)]

Correction, one also has to specify the interface(s) on which to listen for replies (despite what the man page says), so the correct syntax would be:

  dhcrelay -d -i eth0 -i eth1 -i eth2 -i eth3 172.20.0.10 172.20.0.1

[Harald Jensås (harald-jensas)]

@Ian

Did you test the above?

I cannot get dhcprelay to work with the version shipped in CentOS|RHEL) I have to download source code from ICS and compile the new version (or use Fedora).

What happens with dhcrelay shipped in CentOS is:
 - dhcp request recived by relay
 - relay forwards request
 - dhcpserver recives request
 - dhcpserver responds to request
 - dhcprelay sees the resopons
 - ISSUE: The dhcp respons never gets to the client

[Ian Pilcher (arequipeno)]

@Harald -

Yes. I did get the dhcrelay in CentOS 7.5 to work. As noted in comment #1, I had to specifically tell dhcrelay to listen on the *response* network, as well as the request network.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/616390

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/616390
Committed: https://git.openstack.org/cgit/openstack/tripleo-docs/commit/?id=d3699dbe872354bdbab0ad70d2eb0698e186de8f
Submitter: Zuul
Branch: master

commit d3699dbe872354bdbab0ad70d2eb0698e186de8f
Author: Harald Jensås <email address hidden>
Date: Thu Nov 8 02:09:59 2018 +0100

    Add dhcrelay example to using old syntax

    "DHCP relay configuration (Example)" section works for
    more recent versions 4.3.6 (in Fedora), but it doesn't
    work with the version in 4.2.5 (CentOS 7).

    Add example configuration for version 4.2.5 (Centos)
    as well.

    Closes-Bug: #1774637
    Change-Id: Ifa828c572d3c6dfc408d2fbebc52f4aa2c571615