Reg: dhcp service unresponsive frequently

[Purva Rawan]

On January 25, 2020 at 10:57 PM Niall O'Reilly <niall.oreilly at ucd.ie> wrote:
> On 24 Jan 2020, at 7:14, Purva Rawan wrote:
>
> > We have not configured dhcp relay agent in both dhcp server's
> > configuration .
>
> That would be right; see below: the relay belongs to the network, not to
> the
> server.
>
> > In one of the server ,dhcp service listening on each interfaces.
> > For another dhcp server ,dhcp relay agent is serving through Layer 3
> > switch.
> >
> > But we are facing this issue for both the servers.
>
> It may help to think about this from the client back to the server,
> rather than from the server(s) outwards.
>
> I don't have a good picture of your network topology, or where the
> relays and servers are sitting, or what experience you have, so I may
> be explaining at the wrong level. If so, apologies.
>
> Each client is connected to a layer-2 network, and needs a local DHCP
> service on this network.
>
> The local DHCP service must be provided either by a relay or by a
> server;
> it's unusual to have a server connected to every client network.
>>>> Yes ,clients are connected to layer-2 network.
>
> The relay is typically part of the router configuration.
>
> Each relay must be configured with the address of one or more servers;
> one is enough; a second gives resilience; I wouldn't suggest more.
>
> The server(s) can be on a network where no clients are connected; except
> for very simple topologies, I prefer to keep the server on a non-client
> network.
>
> Each relay must be able to reach, and be reachable from, the server(s);
> access lists and routing errors can obstruct reachability, perhaps
> asymmetrically.
>
> Each client network must be specified in the server configuration.
>
> Log entries on the server will show you what the server thinks is going
> on.
> You should see the DORA sequence: DISCOVER, OFFER, REQUEST, ACK; for
> renewals, you'll normally just see REQUEST, ACK.
> >>>>>>> We are able to see DORA sequence in logs

> If you know or expect that the client is sending DISCOVER, but don't see
> it in the server log, then you'll need to look at your network and work
> out why the DISCOVER is not reaching the server either from the relay or
> from a client on the same network as the server.
>
> If you see OFFER in the server logs, but no REQUEST, you'll need to look
> at the network in the opposite direction, and work out why the OFFER is
> not reaching the client or relay.
>

 It was working fine since last 6-7 years.But from last 3 4 months ,dhcp service
stops intermittently.
Point to be noted that the configuration of DHCP is in LDAP database.

We have observed following things  when dhcp service stopped working suddenly

1. slapd service remains working and logs captured in slapd.logs file
2. dhcp logs not getting populated.


Regards,
Purva Rawan

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