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On January 25, 2020 at 10:57 PM Niall O'Reilly <niall.oreilly@ucd.ie> wrote:
<br/>> On 24 Jan 2020, at 7:14, Purva Rawan wrote:
<br/>>
<br/>> > We have not configured dhcp relay agent in both dhcp server's
<br/>> > configuration .
<br/>>
<br/>> That would be right; see below: the relay belongs to the network, not to
<br/>> the
<br/>> server.
<br/>>
<br/>> > In one of the server ,dhcp service listening on each interfaces.
<br/>> > For another dhcp server ,dhcp relay agent is serving through Layer 3
<br/>> > switch.
<br/>> >
<br/>> > But we are facing this issue for both the servers.
<br/>>
<br/>> It may help to think about this from the client back to the server,
<br/>> rather than from the server(s) outwards.
<br/>>
<br/>> I don't have a good picture of your network topology, or where the
<br/>> relays and servers are sitting, or what experience you have, so I may
<br/>> be explaining at the wrong level. If so, apologies.
<br/>>
<br/>> Each client is connected to a layer-2 network, and needs a local DHCP
<br/>> service on this network.
<br/>>
<br/>> The local DHCP service must be provided either by a relay or by a
<br/>> server;
<br/>> it's unusual to have a server connected to every client network.
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>>>> Yes ,clients are connected to layer-2 network.
<br/>>
<br/>> The relay is typically part of the router configuration.
<br/>>
<br/>> Each relay must be configured with the address of one or more servers;
<br/>> one is enough; a second gives resilience; I wouldn't suggest more.
<br/>>
<br/>> The server(s) can be on a network where no clients are connected; except
<br/>> for very simple topologies, I prefer to keep the server on a non-client
<br/>> network.
<br/>>
<br/>> Each relay must be able to reach, and be reachable from, the server(s);
<br/>> access lists and routing errors can obstruct reachability, perhaps
<br/>> asymmetrically.
<br/>>
<br/>> Each client network must be specified in the server configuration.
<br/>>
<br/>> Log entries on the server will show you what the server thinks is going
<br/>> on.
<br/>> You should see the DORA sequence: DISCOVER, OFFER, REQUEST, ACK; for
<br/>> renewals, you'll normally just see REQUEST, ACK.
<br/>> >>>>>>> We are able to see DORA sequence in logs
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<br/>> If you know or expect that the client is sending DISCOVER, but don't see
<br/>> it in the server log, then you'll need to look at your network and work
<br/>> out why the DISCOVER is not reaching the server either from the relay or
<br/>> from a client on the same network as the server.
<br/>>
<br/>> If you see OFFER in the server logs, but no REQUEST, you'll need to look
<br/>> at the network in the opposite direction, and work out why the OFFER is
<br/>> not reaching the client or relay.
<br/>>
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<span style="font-size: 9pt;"> It was working fine since last 6-7 years.But from last 3 4 months ,dhcp service stops intermittently.</span>
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<span style="font-size: 9pt;">Point to be noted that the configuration of DHCP is in LDAP database.</span>
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<span style="font-size: 9pt;"> </span>
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<span style="font-size: 9pt;">We have observed following things when dhcp service stopped working suddenly </span>
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<span style="font-size: 9pt;"> </span>
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<span style="font-size: 9pt;">1. slapd service remains working and logs captured in slapd.logs file </span>
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<span style="font-size: 9pt;"></span>
<span style="font-size: 9pt;">2. dhcp logs not getting populated.</span>
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<span style="font-size: 9pt;"> </span>
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<span style="font-size: 9pt;"> </span>
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<span style="font-size: 9pt;">Regards,</span>
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<span style="font-size: 9pt;">Purva Rawan</span>
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