Interesting.  I think that initial offer is a broadcast packet…..maybe that 
“reliable multicast” setting affects broadcast as well?

 

From: AF <af-boun...@af.afmug.com> On Behalf Of Nate Burke
Sent: Saturday, March 19, 2022 7:38 AM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Subject: Re: [AFMUG] EPMP1000 and DHCP failures

 

I was able to get a packet capture while it while it was happening.  Client had 
been running fine for about 3 days before it started erroring (3 hour DHCP 
Lease).  Nothing was logged with the firewall rules on the Mikrotik doing the 
DHCP Server.

I have a mikrotik between the 450SM an the EPMP AP, I was able to run a packet 
capture from there.  I ran it on the interface of the EPMP radio.  It was 
showing the DHCP Discover being sent to the Server, and the DHCP Offer being 
sent back to the client, but that was it, no DHCP Request Packet coming from 
the EPMP Interface.  

On the EPMP AP,  I changed the 'Reliable Multicast' from Disabled to Enabled.  
And the client immediately got a DHCP lease after saving that (No AP Reboot).  
The DHCP Request Packet came back from the client as soon as the Discover/offer 
packets were sent.  I'm not convinced that was the issue, as I don't have it 
enabled on ay other EPMP radio on the network.  It seemed more like making a 
change in the AP reset something in the EPMP network stack.  It's just strange 
that it happens so randomly.

On 3/14/2022 7:24 PM, Steve Jones wrote:

The mikrotik that handles the dhcp relay or dhcp, log any input firewall rules 
and see if its dropping the packets

 

On Mon, Mar 14, 2022, 7:03 PM Nate Burke <n...@blastcomm.com 
<mailto:n...@blastcomm.com> > wrote:

Just had it happen on a newly installed EPMP1000<->EPMP1000 link.  AP and SM 
are both 2.4 non-GPS radios.  Feed to site is a 450B off a450M AP.  Relay from 
barn to house using 2.4 EPMP 1000 radios.  

Was working fine when I left,  3 hours later, DHCP lease timed out (Mikrotik 
DHCP Lease time) and would not get new lease.  Rebooting the 1000 Radio acting 
as the AP fixed it.  If it happens again, I'll try to get a packetcapture off 
it.

On 3/9/2022 10:14 AM, Steve Jones wrote:

the mikrotik is dhcp relay, BMI is the dhcp server

 

On Wed, Mar 9, 2022 at 10:07 AM Josh Luthman <j...@imaginenetworksllc.com 
<mailto:j...@imaginenetworksllc.com> > wrote:

Oh this is on the DHCP server, sorry.

 

On Wed, Mar 9, 2022 at 10:31 AM Steve Jones <thatoneguyst...@gmail.com 
<mailto:thatoneguyst...@gmail.com> > wrote:

we have to have it for dhcp relay to keep functioning. otherwise it 
periodically stops working from EPMP APs, I never knew why, mikrotik had no 
answer, but it would suddenly get caught up in non ACL drops add action=accept 
chain=input comment="ALLOW DHCP UDP 67" dst-port=67 log-prefix=dhcp protocol=udp

 

On Wed, Mar 9, 2022 at 8:12 AM Josh Luthman <j...@imaginenetworksllc.com 
<mailto:j...@imaginenetworksllc.com> > wrote:

The input chain is to the Mikrotik itself, ie the IP address that it would 
theoretically get from the DHCP server.  I was thinking of a managed Mikrotik 
as a demarc to the customer's stuff (so forward chain).

 

On Tue, Mar 8, 2022 at 7:57 PM Steve Jones <thatoneguyst...@gmail.com 
<mailto:thatoneguyst...@gmail.com> > wrote:

I had this issue a long time ago, id like to think that it was a firmware 
revision that resolved the issue, but it was a long time ago and im partially 
retarded.  

If you have a mikrotik, add an input rule allow udp 67. Just for kicks. It 
might be this issue that i have that policy for.

 

On Tue, Mar 8, 2022, 4:22 PM Josh Luthman <j...@imaginenetworksllc.com 
<mailto:j...@imaginenetworksllc.com> > wrote:

Raise a ticket with Cambium and explain the situation?  If you could get pcap 
that would show what's missing.  Do you have a Tik behind any SM with the issue 
by chance?

 

On Tue, Mar 8, 2022 at 4:05 PM Nate Burke <n...@blastcomm.com 
<mailto:n...@blastcomm.com> > wrote:

No DHCP Relay, just local DHCP Server on the mikrotik on the bridge that all 
the AP's are part of. 

No MAC limit on the SM's  

When it exhibits itself, a customer who has been running for weeks will timeout 
their lease, and the mikrotik will just go to 'offered'  Rebooting the AP 
always fixes it.  

On 3/8/2022 1:18 PM, dmmoff...@gmail.com <mailto:dmmoff...@gmail.com>  wrote:

I was wondering about broadcast rate limit.  That would apply to a DHCP 
discover, but not to a renewal.  ….but either the MAC limit or broadcast limit 
would clear when rebooting the SM, and he says rebooting the SM has no effect.

 

Is DHCP running on the port that the AP is plugged into, or is there a DHCP 
relay involved?

 

 

From: AF  <mailto:af-boun...@af.afmug.com> <af-boun...@af.afmug.com> On Behalf 
Of Josh Luthman
Sent: Tuesday, March 08, 2022 12:43 PM
To: AnimalFarm Microwave Users Group  <mailto:af@af.afmug.com> <af@af.afmug.com>
Subject: Re: [AFMUG] EPMP1000 and DHCP failures

 

Do you have the SM limited on MACs?  Look at Ethernet Port Security on config > 
network.

 

On Tue, Mar 8, 2022 at 12:32 PM Nate Burke <n...@blastcomm.com 
<mailto:n...@blastcomm.com> > wrote:

I've experienced this issue randomly, and haven't been able to track 
down a cause.  Wondering if anyone else has come across something similar.

Mikrotik DHCP Server.  EPMP1000 GPS AP,  Force 300 SM.

At a random time, one or More Force 300 SM's on the AP will lose the 
ability to hand out a DHCP Address to the client.  The Mikrotik just 
shows 'Offered'

Rebooting or powercycling the SM has no effect.  If the SM Connects to a 
different sector, then DHCP is immediately handed out.  If the AP 
reboots, and the SM reconnects, then DHCP is immediately handed out.  If 
the SM is set for NAT mode, it can get a DHCP Address just fine, but 
switching back to bridge, the Customer router will not get DHCP.

I've experienced this from 4.4.3 all the way up to 4.6.3.  It always 
seems to be an EPMP1000 AP with a Foce300 SM, but does not affect every 
Force300 SM at the same time.

At least now I know when I start having this problem to go reboot the AP.

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