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martinii
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DHCP alert every minute on all vlans

Mon Sep 20, 2021 3:18 pm

Hello all,

I have few vlans with bridge filtering configured on Mikrotik RB1100AHx2. I've set dhcp alerts:
Flags: X - disabled, I - invalid 
 #   INTERFACE                      VALID-SERVER      ON-ALERT       ALERT-TIMEOUT
 0   VLAN_100_APMGT                 4C:5E:0C:E3:92:A9                1h
 1   VLAN_010_CCTV                  4C:5E:0C:E3:92:A9                1h
 2   VLAN_050_ELWIFI                4C:5E:0C:E3:92:A9                1h
 3   VLAN_060_ELWLAN                4C:5E:0C:E3:92:A9                1h

and run dhcp debug logging. Now in log section I have DHCP alert every single minute:

Image

Image

What is going on? This is my DHCP settings:
Flags: D - dynamic, X - disabled, I - invalid 
 #    NAME                 INTERFACE               RELAY           ADDRESS-POOL                   LEASE-TIME ADD-ARP
 0    dhcp1_LAN            bridge1_lan                             dhcp_pool1_LAN                 3d
 1    dhcp2_CCTV           VLAN_010_CCTV                           dhcp_pool2_VLAN_CCTV           3d
 2    dhcp3_SALTO          VLAN_020_SALTO                          dhcp_pool3_VLAN_SALTO          3d
 3    dhcp4_TEL            VLAN_030_TEL                            dhcp_pool4_VLAN_TEL            3d
 4    dhcp5_POK7           VLAN_040_POK7                           dhcp_pool5_VLAN_POK7           3d
 5    dhcp6_ELWIFI         VLAN_050_ELWIFI                         dhcp_pool6_VLAN_ELWIFI         3d
 6    dhcp7_ELWLAN         VLAN_060_ELWLAN                         dhcp_pool7_VLAN_ELWLAN         3d
 7    dhcp8_APMGT          VLAN_100_APMGT                          dhcp_pool8_VLAN_APMGT          3d



Flags: D - dynamic 
 #   ADDRESS            GATEWAY         DNS-SERVER                                                  WINS-SERVER     DOMAIN
 0   192.168.0.0/24     192.168.0.1     
 1   192.168.10.0/24    192.168.10.1    8.8.8.8,8.8.4.4
 2   192.168.20.0/24    192.168.20.1    8.8.8.8,8.8.4.4
 3   192.168.30.0/24    192.168.30.1    8.8.8.8,8.8.4.4
 4   192.168.40.0/24    192.168.40.1    8.8.8.8,8.8.4.4
 5   192.168.50.0/24    192.168.50.1    8.8.8.8,8.8.4.4
 6   192.168.60.0/24    192.168.60.1    8.8.8.8,8.8.4.4
 7   192.168.100.0/24   192.168.100.1   8.8.8.8,8.8.4.4


My bridge configuration:

Flags: X - disabled, R - running 
 0 R name="bridge1_lan" mtu=1500 actual-mtu=1500 l2mtu=1500 arp=enabled arp-timeout=auto mac-address=4C:5E:0C:E3:92:AB protocol-mode=none fast-forward=yes igmp-snooping=no auto-mac=yes ageing-time=5m vlan-filtering=no dhcp-snooping=no 

 1 R name="bridge_vlan" mtu=auto actual-mtu=1500 l2mtu=1598 arp=enabled arp-timeout=auto mac-address=4C:5E:0C:E3:92:A9 protocol-mode=none fast-forward=yes igmp-snooping=no auto-mac=no admin-mac=4C:5E:0C:E3:92:A9 ageing-time=5m vlan-filtering=yes 
     ether-type=0x8100 pvid=1 frame-types=admit-all ingress-filtering=no dhcp-snooping=no 

 2 R name="bridge_wan" mtu=auto actual-mtu=1500 l2mtu=1500 arp=enabled arp-timeout=auto mac-address=4C:5E:0C:E3:92:A6 protocol-mode=none fast-forward=no igmp-snooping=no auto-mac=yes ageing-time=5m vlan-filtering=no dhcp-snooping=no


Flags: X - disabled, D - dynamic 
 #   BRIDGE             VLAN-IDS  CURRENT-TAGGED        CURRENT-UNTAGGED
 0   bridge_vlan        10        bridge_vlan
                                  VLAN_bonding
 1   bridge_vlan        20        bridge_vlan
                                  VLAN_bonding
 2   bridge_vlan        30        bridge_vlan
                                  VLAN_bonding
 3   bridge_vlan        40        bridge_vlan
                                  VLAN_bonding
 4   bridge_vlan        50        bridge_vlan
                                  VLAN_bonding
 5   bridge_vlan        60        bridge_vlan
                                  VLAN_bonding
 6   bridge_vlan        100       bridge_vlan
                                  VLAN_bonding
 7   bridge_vlan        70        bridge_vlan
                                  VLAN_bonding
 8 D bridge_vlan        1                               bridge_vlan
                                                        VLAN_bonding

Recently I've disconnected everything from Mikrotik, disabled lan and wan bridge - left only vlan bridge but the "every minute alerts" still showed in log.
Last edited by martinii on Mon Sep 20, 2021 4:42 pm, edited 1 time in total.
 
tdw
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 3:54 pm

DHCP alert works by sending a probe for other DHCP servers. You are seeing a debug message indicating the discovery packets are being transmitted, stop logging at debug level.
 
martinii
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 4:24 pm

So these logs are nothing extraordinary? Are they just the result of checking the dhcp debug logging option?
 
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 5:04 pm

What was the intent of logging dhcp alerts. What issue prompted you to set the log??
Offering without success, yes I see those two and dont know if its an MT issue, I suspect they are issues to do with IOT devices or apple devices.
Last edited by anav on Mon Sep 20, 2021 9:05 pm, edited 1 time in total.
 
martinii
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 9:03 pm

@anav, this is actually the reason:

Image
 
Zacharias
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 9:13 pm

RouterOS version ?
 
martinii
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 9:32 pm

6.48.4
 
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 10:04 pm

ok, and what does the debug log show at the time of the warning event ?
 
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Re: DHCP alert every minute on all vlans

Mon Sep 20, 2021 10:06 pm

So these logs are nothing extraordinary? Are they just the result of checking the dhcp debug logging option?
Yes, just a side-effect from enabling DHCP debugging to track down the lease offered without success issue (there are various reasons for that, mixing WiFi ethernet bridges from differing vendors is often a cause as they don't pass all the layer 2 addresses without compatible WDS or bridging implementations)
 
martinii
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Re: DHCP alert every minute on all vlans

Tue Sep 21, 2021 10:29 am

ok, and what does the debug log show at the time of the warning event ?

Here's an example:

09:19:43 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:43 dhcp,debug,packet     secs = 3 
09:19:43 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:43 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:43 dhcp,debug,packet     Msg-Type = discover 
09:19:43 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:43 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:43 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:43 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:43 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:43 dhcp,debug lease found, offered, offer 
09:19:43 dhcp,debug 5 offers in a row => no response, restarting with unicast 
09:19:43 dhcp,warning dhcp6_ELWIFI offering lease 192.168.50.77 for 22:BF:D0:D3:31:FA without success 
09:19:43 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 192.168.50.77 
09:19:43 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:43 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:43 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:43 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:43 dhcp,debug,packet     Msg-Type = offer 
09:19:43 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:43 dhcp,debug,packet     Address-Time = 259200 
09:19:43 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:43 dhcp,debug,packet     Router = 192.168.50.1 
09:19:43 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4 
09:19:43 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:43 dhcp,debug,packet     secs = 6 
09:19:43 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:43 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:43 dhcp,debug,packet     Msg-Type = discover 
09:19:43 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:43 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:43 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:43 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:43 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 


Maybe better perspective:
09:19:36 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:36 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:36 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:36 dhcp,debug,packet     Msg-Type = discover 
09:19:36 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:36 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:36 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:36 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:36 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:36 dhcp,debug lease found, bound, offer 
09:19:36 dhcp,info dhcp6_ELWIFI deassigned 192.168.50.77 from 22:BF:D0:D3:31:FA 
09:19:36 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 255.255.255.255 
09:19:36 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:36 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:36 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:36 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:36 dhcp,debug,packet     Msg-Type = offer 
09:19:36 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:36 dhcp,debug,packet     Address-Time = 259200 
09:19:36 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:36 dhcp,debug,packet     Router = 192.168.50.1 
09:19:36 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4 
09:19:36 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:36 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:36 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:36 dhcp,debug,packet     Msg-Type = discover 
09:19:36 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:36 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:36 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:36 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:36 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:36 dhcp,debug lease found, offered, offer 
09:19:36 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 255.255.255.255 
09:19:36 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:36 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:36 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:36 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:36 dhcp,debug,packet     Msg-Type = offer 
09:19:36 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:36 dhcp,debug,packet     Address-Time = 259200 
09:19:36 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:36 dhcp,debug,packet     Router = 192.168.50.1 
09:19:36 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4 
09:19:37 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:37 dhcp,debug,packet     secs = 1 
09:19:37 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:37 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:37 dhcp,debug,packet     Msg-Type = discover 
09:19:37 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:37 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:37 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:37 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:37 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:37 dhcp,debug lease found, offered, offer 
09:19:37 dhcp,debug 3 offers in a row 
09:19:37 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 255.255.255.255 
09:19:37 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:37 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:37 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:37 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:37 dhcp,debug,packet     Msg-Type = offer 
09:19:37 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:37 dhcp,debug,packet     Address-Time = 259200 
09:19:37 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:37 dhcp,debug,packet     Router = 192.168.50.1 
09:19:37 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4 
09:19:37 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:37 dhcp,debug,packet     secs = 1 
09:19:37 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:37 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:37 dhcp,debug,packet     Msg-Type = discover 
09:19:37 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:37 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:37 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:37 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:37 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:37 dhcp,debug lease found, offered, offer 
09:19:37 dhcp,debug 4 offers in a row 
09:19:37 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 255.255.255.255 
09:19:37 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:37 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:37 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:37 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:37 dhcp,debug,packet     Msg-Type = offer 
09:19:37 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:37 dhcp,debug,packet     Address-Time = 259200 
09:19:37 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:37 dhcp,debug,packet     Router = 192.168.50.1 
09:19:37 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4 
09:19:38 dhcp,debug dhcp6_ELWIFI received discover id 1502611673 from 0.0.0.0 '1:22:bf:d0:d3:31:fa' 
09:19:38 dhcp,debug,packet     secs = 1 
09:19:38 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:38 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:38 dhcp,debug,packet     Msg-Type = discover 
09:19:38 dhcp,debug,packet     Client-Id = 01-22-BF-D0-D3-31-FA 
09:19:38 dhcp,debug,packet     Max-DHCP-Message-Size = 1500 
09:19:38 dhcp,debug,packet     Class-Id = "android-dhcp-10" 
09:19:38 dhcp,debug,packet     Host-Name = "Galaxy-A10" 
09:19:38 dhcp,debug,packet     Parameter-List = Subnet-Mask,Router,Domain-Server,Domain-Name,Interface-MTU,Broadcast-Address,Address-Time,Renewal-Time,Rebinding-Time,Vendor-Specific 
09:19:38 dhcp,debug lease found, offered, offer 
09:19:38 dhcp,debug 5 offers in a row => no response, restarting with unicast 
09:19:38 dhcp,warning dhcp6_ELWIFI offering lease 192.168.50.77 for 22:BF:D0:D3:31:FA without success 
09:19:38 dhcp,debug dhcp6_ELWIFI sending offer with id 1502611673 to 192.168.50.77 
09:19:38 dhcp,debug,packet     ciaddr = 0.0.0.0 
09:19:38 dhcp,debug,packet     yiaddr = 192.168.50.77 
09:19:38 dhcp,debug,packet     siaddr = 192.168.50.1 
09:19:38 dhcp,debug,packet     chaddr = 22:BF:D0:D3:31:FA 
09:19:38 dhcp,debug,packet     Msg-Type = offer 
09:19:38 dhcp,debug,packet     Server-Id = 192.168.50.1 
09:19:38 dhcp,debug,packet     Address-Time = 259200 
09:19:38 dhcp,debug,packet     Subnet-Mask = 255.255.255.0 
09:19:38 dhcp,debug,packet     Router = 192.168.50.1 
09:19:38 dhcp,debug,packet     Domain-Server = 8.8.8.8,8.8.4.4
 
martinii
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Re: DHCP alert every minute on all vlans

Wed Sep 22, 2021 8:00 pm

So? Any hint?
 
Zacharias
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Re: DHCP alert every minute on all vlans

Wed Sep 22, 2021 8:29 pm

Well, how often you got this kind of problem ?
It happens to see from time to time warning messages like this, but nothing permanent...

The client device might deny the offer from the DHCP as well for some reasons, so offering lease without success does not necessarily indicate a problem on the Network side ...

Also in case of Wireless Clients those messages seem easier to appear, imagine a client discovering a DHCP server but due to bad signal disconnecting from the network, the DHCP would never reach back to that device and offer its lease ...

I would not be worried of such a message if it was not happening really often...
Last edited by Zacharias on Wed Sep 22, 2021 8:35 pm, edited 1 time in total.
 
tdw
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Re: DHCP alert every minute on all vlans

Wed Sep 22, 2021 8:31 pm

Nothing wrong with the Mikrotik, it is receiving a discover and sending an offer - that is either not getting to or being ignored by the client.
 
martinii
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Re: DHCP alert every minute on all vlans

Thu Sep 23, 2021 9:31 am

Additionally i can say:
1. The problem refferes only to wireless networks.
2. The problem started when I set up the vlans - I set up 2 networks: for emploees and guests. I never saw this problem before setting up vlans and all the hardware was the same as now.
3. This mainly applies to mobile phones, but sometimes to laptops as well. The brand doesn't matter.
4. It happened to me too. I have a Xiaomi mobile phone and from my point of view I got the error "Unable to get IP address".
5. Problem occurs randomly - sometimes once a week and sometimes several dozen a DAY.
 
Zacharias
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Re: DHCP alert every minute on all vlans

Sun Sep 26, 2021 11:04 am

How are VLANs configured ?
Also a design of your network topology would help ...
 
martinii
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Re: DHCP alert every minute on all vlans

Mon Sep 27, 2021 11:39 am

Here are information you asked for. Vlan bridge settings:
 1 R name="bridge_vlan" mtu=auto actual-mtu=1500 l2mtu=1598 arp=enabled arp-timeout=auto mac-address=4C:5E:0C:E3:92:A9 protocol-mode=none fast-forward=no igmp-snooping=no auto-mac=no admin-mac=4C:5E:0C:E3:92:A9 ageing-time=5m vlan-filtering=yes ether-type=0x8100 pvid=1 frame-types=admit-all ingress-filtering=no dhcp-snooping=no

Vlan interfaces settings:
 #   NAME                   MTU ARP             VLAN-ID INTERFACE
 0 R VLAN_010_CCTV         1500 enabled              10 bridge_vlan
 1 R VLAN_020_SALTO        1500 enabled              20 bridge_vlan
 2 R VLAN_030_TEL          1500 enabled              30 bridge_vlan
 3 R VLAN_040_POK7         1500 enabled              40 bridge_vlan
 4 R VLAN_050_ELWIFI       1500 enabled              50 bridge_vlan
 5 R VLAN_060_ELWLAN       1500 enabled              60 bridge_vlan
 6 R VLAN_070_LAN          1500 enabled              70 bridge_vlan
 7 R VLAN_100_APMGT        1500 enabled             100 bridge_vlan

This is a network topology:
Image
 
tdw
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Re: DHCP alert every minute on all vlans

Mon Sep 27, 2021 11:59 am

As this only affects wirelessly connected devices have you checked the Ubiquiti forum posts regarding issues when mixing their APs with third-party DHCP servers?
 
Zacharias
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Re: DHCP alert every minute on all vlans

Mon Sep 27, 2021 3:12 pm

As this only affects wirelessly connected devices have you checked the Ubiquiti forum posts regarding issues when mixing their APs with third-party DHCP servers?
The issue can be VLAN related as well ...

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