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Title: The EG3250 DHCP offer IP addresses occupied by hosts. [Print this page]

Author: roman_moi@mail. Time: 2024-8-12 17:01
Title: The EG3250 DHCP offer IP addresses occupied by hosts.
The DHCP server, when configured for Permanent
ip lease, offer addresses that are already occupied.

Author: v-xiewenyu@ruij Time: 2024-8-12 17:13
Dear Sir,
Before DHCP Server allocates an address, it will ping probe the address to ensure that it is not in use. If probed, and found that the address is occupied will trigger a conflict alert. In addition to generating the above logs, you can also see the conflict logs through the showip dhcp confict. Since the conflict detection is before allocation, generally speaking, this alarm has no business impact.
Best regards,
Lex

Author: roman_moi@mail. Time: 2024-8-12 17:59

GTAC-Lex replied at 2024-8-12 17:13
Dear Sir,
Before DHCP Server allocates an address, it will ping probe the address to ensure that it ...

The DHCP server should not offer already allocated IP addresses. This is not right. There is only one dhcp server on my network.

Author: v-xiewenyu@ruij Time: 2024-8-12 19:53

Роман Филиппов replied at 2024-8-12 17:59
The DHCP server should not offer already allocated IP addresses. This is not right. There is only ...

Dear，
The possible reasons for this phenomenon are:
1. Some terminals are configured with static addresses, and there is a conflict in gateway DHCP allocation.
2. Illegal DHCP Server exists in the network.
3. When the gateway restarts or the DHCP Server configuration changes, the address pool on the server side is released, but the terminal is still using it.
Corresponding solutions:
1. The conflict in this scenario usually generates only a small number of conflict logs, and the IP of the conflict is relatively fixed. You can check the mac table entries on each switch through the mac information in the log, find the terminal, and change the address acquisition method to DHCP. If the network is mainly wireless terminals and the terminal cannot be found, you can block access by adding the mac of the illegal terminal to the blacklist on the AP.
2. It is necessary to map the network structure to find the access location of the illegal DHCP Server and shut it down. If the network structure is complex and it is difficult to find the illegal DHCP Server, it is recommended to turn on DHCP Snooping on all the switches in the network. DHCP Snooping only trusts the legal uplink port.
3. When the gateway undergoes reboot or the DHCP Server configuration changes (such as IP pool range change), the address pool on the server side will be released, but the terminal may still be in use. At this time, there will be a bulk address conflict. Unlike the DHCP Server conflict, this scenario is generally after a peak business period, the conflict log will be significantly reduced, and the business will not have a serious impact.
If there is no business impact, it is recommended to maintain observation, and after a peak business period, see if the alarm still exists. If it continues to exist and there is no illegal DHCP Server, contact an online engineer to assist in troubleshooting.
regards,
Lex

Author: roman_moi@mail. Time: 2024-8-14 15:19
Edited by Роман Филиппов at 2024-8-14 20:05

GTAC-Lex replied at 2024-8-12 19:53
Dear，
The possible reasons for this phenomenon are:
1. Some terminals are configured with static ...

Here is my DHCP server settings:

But i receive yhis errors:

Al hosts in my network recived ip adresses dynamicaly, dhcp is only one in this network, also there is no static ip adresses.
There is problem with dhcp.
Why does Gateway start giving out new IP addresses when he is rebooted?

Author: v-shaojinren@ru Time: 2024-8-19 10:04

Роман Филиппов replied at 2024-8-14 15:19
GTAC-Lex replied at 2024-8-12 19:53
Dear，
The possible reasons for this phenomenon are:

Dear user,
I would recommend to check if these IP addresses are binded to certain devices via the CLI command "show ip dhcp binding".

Input the CLI commands in the Cloud:

Input the CLI commands in the CLI interface:

If the the IP addresses on the DHCP server are binded to terminals, the terminals
will need to be configured to obtain the ip address dynamically.

Author: roman_moi@mail. Time: 2024-8-19 12:18

GTAC-Ryan replied at 2024-8-19 10:04
Dear user,
I would recommend to check if these IP addresses are binded to certain devices via the ...

I have configured the issuance of ip - permanent, how can ip be issued again?

Author: wengjialong@rui Time: 2024-8-19 13:14

Роман Филиппов replied at 2024-8-19 12:18
I have configured the issuance of ip - permanent, how can ip be issued again?

Hi, Роман Филиппов

If the EG is online on Ruijie Cloud, please check if there is multiple DHCP servers issue in AI Diagnostics.
If there is a second DHCP server, please locate the device according to the detected MAC address and disable its DHCP service or you may enable DHCP snooping on the switches.
Please also check if there is any alarms of IP conflict, you may also locate the devices with conflicting IP according to their MAC address and check if any of them is using static IP.
If the issue persists, you may also try to reduce the DHCP pool size.

Best regards,
Jayden

Author: roman_moi@mail. Time: 2024-8-19 15:50

GTAC-Jayden replied at 2024-8-19 13:14
Hi, Роман Филиппов

If the EG is online on Ruijie Cloud, please check if there is mul ...

Judging by your answers, you either don’t understand what I wrote or don’t read what I added in the comments.
I answer again: there is only one DHCP server on the network, all hosts are configured with dynamic IPs. dhcp lease time is permanent.

Author: guominxiang@rui Time: 2024-8-19 16:11

Роман Филиппов replied at 2024-8-19 15:50
Judging by your answers, you either don’t understand what I wrote or don’t read what I added in ...

Hello,

I'm sorry for the confusion.
What my colleague is trying to say is that it is possible that other users on your network have accidentally enabled the DHCP server function, or have accidentally connected to a device that has DHCP server function, and you have not noticed it.
You can check according to the method provided by my colleague.

If the issue still exists after you check all these steps, please talk with me again and share the screenshot of your checking result. I would be glad to help you in Community.

Best regards,
Micca

Author: roman_moi@mail. Time: 2024-8-19 16:49

GTAC-Micca replied at 2024-8-19 16:11
Hello,

I'm sorry for the confusion.

There is no live users in my network, only asic miners.

Author: luyoukai@ruijie Time: 2024-8-20 15:57

Роман Филиппов replied at 2024-8-19 16:49
Judging by your answers, you either don’t understand what I wrote or don’t read what I added in ...

If the EG3250 DHCP still offers IP addresses occupied by hosts.

please try this command:clear ip dhcp conflict.

let these addresses be allocated again.
And check whether the warning shows again.

Author: roman_moi@mail. Time: 2024-8-27 13:48

GTAC-Blake replied at 2024-8-20 15:57
If the EG3250 DHCP still offers IP addresses occupied by hosts.

Please explain the phenomenon:
When the gateway is rebooted or the DHCP server configuration is changed, the server-side address pool is freed, but the terminal still uses it.
Why does restarting the gateway reset the DHCP lease?

Author: v-xiewenyu@ruij Time: 2024-8-27 14:00

Роман Филиппов replied at 2024-8-27 13:48
Please explain the phenomenon:
When the gateway is rebooted or the DHCP server configuration is c ...

Dear sir,
Is your DHCP server on the gateway? If so, the DHCP lease information is stored on the DHCP server, and the device restart will naturally reset the DHCP.

Best regards,

Lex

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