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Problems with dhcp and dn...

Problems with dhcp and dns

Created: Jun 10, 2020 14:11:38Latest reply: Jul 5, 2020 14:54:23 741 5 0 0 0
  Rewarded HiCoins： 1 (problem resolved)
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Hi,


I currently have a s5720-52x stack, the current number of installed switches is 5.

The main dhcp server, firewall and router is Cisco Meraki mx84.


Users are reporting network performance issues randomly, network starts working slow for 5/10 minutes and finally it recovers i.e internet navigation. 

I discarted a isp problem,


Also we detected that the access points (cisco meraki mr18 and mr33) loses the connectivity.

It seems they are sending dhcp discovers and the dhcp server is answering but the aps finally never reiceves the ack and because this the ap goes in repetitor mode affecting to the network performance for end users.


Looking the cisco meraki documentation...

        A gateway AP is an access point that has a wired interface configured with an IP address, that is connected to the         to the LAN and has a route to the Internet. The AP only converts to a repeater when one of the following is true:

      • The AP cannot receive an ARP reply packet from the default gateway on the LAN which is usually a local firewall or router

      • The AP is unable to obtain a valid IP address via DHCP


To discard problems with vlan or something else for the wifi I created a separated management vlan (160) for the aps with a dedicated dhcp scope, but the problem persists.

This is the current configuration for the ap ports:

 description wifi

 port link-type trunk

 port trunk pvid vlan 160

 port trunk allow-pass vlan 2 to 4094


The issue is happening with wired computers and also with wifi so I think we have something wrong in our configuration or maybe a physical problem.

I don't know what could be happening, any advices or ideas? network loop maybe?

How can I troubleshoot?

Thanks in advance.


Best regards

DHCPDHCP Unavailable

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Sapte
Created Jun 11, 2020 07:09:56

Hi @ProaData

This issue can caused by 4 Reason in the below d.


1- AP looses its assigned dhcp ip address,possible reasons for this

    1.1.-DHCP Server stop the broadcasting ip address into the interface
    1.2 -AP can't access DHCP Server if it's needed to prolong ip lease time.
    1.3 -DHCP Server doesn't assign ip address no more since it filled all ip address in ip pool


 2- Packet losses or tranmsision problem occurse between the AP LAN port and distribution network,this cause ARP packet dropping,at this time AP can be seem out of network
    2.1-Check the AP lan port and switch access port if is there any packet missing or interface discarding problem                                                                                                                                        2.2-Check if the Swtitches create loops within network
    2.3-Configure traffis statistics in order to see packet transmission statistics
    2.4-Configure NQA test from AP or Switch to DHCP Server to see if there is any packet loosses.



3- CAPWAP tunnel can't establish between AP and AC,this causes the failure

    3.1 Check capwap tunnel conenction via Cisco WLC or Cloud Based Controller

    3.2  If it's a layer 3 network between AP and Controller don't forget to configure Option 43


4- Normally Cisco APs works in Leightweight AP mode by defaul in order establish CAPWAP with Controller.However a if they can't establish capwap or broke the capwap tunnel during a specific period,they return to work as Autonomous AP in repeater mode.So in order to be sure about this check your  WLC Controller to see CAPWAP situation


Have a nice day !

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2#
jason_hu
jason_hu Admin Created Jun 10, 2020 14:20:19

Hello,
It's nice to meet you in the community.
We're working on your problem. Please be patient.
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3#
ster
ster Created Jun 10, 2020 14:47:16

Hello,
Can you share the configuration of DHCP? Does the peer end receive the IP address assigned by DHCP? Or check whether the IP address assigned by DHCP expires.
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4#
Popeye_Wang
Popeye_Wang Admin Created Jun 11, 2020 06:34:02

Hi,
It seems that your fault is that the AP goes offline abnormally, please refer to the following steps for troubleshooting.
https://info.support.huawei.com/onlinetoolweb/ptmngsys/Web/tsrev_wlan/en/content/wlan/22_edesk_ap_offline_unexpectedly/edesk_ap_offline_unexpectedly_edesk000.html
If this does not work, you are advised to contact the TAC of Huawei and Cisco.
Huawei TAC:https://e.huawei.com/en/service-hotline-query

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5#
Sapte
Sapte Created Jun 11, 2020 07:09:56

Hi @ProaData

This issue can caused by 4 Reason in the below d.


1- AP looses its assigned dhcp ip address,possible reasons for this

    1.1.-DHCP Server stop the broadcasting ip address into the interface
    1.2 -AP can't access DHCP Server if it's needed to prolong ip lease time.
    1.3 -DHCP Server doesn't assign ip address no more since it filled all ip address in ip pool


 2- Packet losses or tranmsision problem occurse between the AP LAN port and distribution network,this cause ARP packet dropping,at this time AP can be seem out of network
    2.1-Check the AP lan port and switch access port if is there any packet missing or interface discarding problem                                                                                                                                        2.2-Check if the Swtitches create loops within network
    2.3-Configure traffis statistics in order to see packet transmission statistics
    2.4-Configure NQA test from AP or Switch to DHCP Server to see if there is any packet loosses.



3- CAPWAP tunnel can't establish between AP and AC,this causes the failure

    3.1 Check capwap tunnel conenction via Cisco WLC or Cloud Based Controller

    3.2  If it's a layer 3 network between AP and Controller don't forget to configure Option 43


4- Normally Cisco APs works in Leightweight AP mode by defaul in order establish CAPWAP with Controller.However a if they can't establish capwap or broke the capwap tunnel during a specific period,they return to work as Autonomous AP in repeater mode.So in order to be sure about this check your  WLC Controller to see CAPWAP situation


Have a nice day !

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6#
cataleyagonzc
cataleyagonzc Created Jul 5, 2020 14:54:23

Experienced
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