Ethernet Switching
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Ethernet Switching

PC isn't able to take DHCP configuration

a week ago

Please I need your help 

I have a juniper switch called A connected to a core direct EX 9204 the core has the configuration to enable DHCP rely on  a server .

some users which connected to switch A and are in the same subnet are able to take from the DHCP pool and some not ,

What is the missing configuration which shall be done to enable all PCs to take from the DHCP pool ?

10 REPLIES 10
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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

Hello HDawood,

 

Not sure if this sounds a configuration issue.  It should be good if you open a case for proper troubleshooting.

 

On the EX9204, monitor the vlan to confirm if the Discover packet is received.

 

>monitor traffic interface irb.x no-resolve size 1500 matching "port 67||68" detail

 

If you don't see the discover packet, then check the configuration on each port to confirm if the vlan was properly configured.

If you see the Discover packet, then you may need to reboot the EX9204.

 

You can also check the DHCP relay statistics and check if errors are incrementing

 

>show dhcp relay statistics

 

Regards,

 

Randall

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

Hi Dawood,

 

Please check the following KB article for troubleshooting DHCP related issues - https://kb.juniper.net/InfoCenter/index?page=content&id=KB23335&actp=METADATA

 

Also, let us know in which step you are stuck so that we can take it up from there.



Thanks,
π00bm@$t€®.
Please, Mark My Solution Accepted if it Helped, Kudos are Appreciated too!!!
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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

Hi HDawood

You should check the bindings of the dhcp relay to confirm if the core is receiving the requests from hosts. If so, you can move to the server to confirm if it is receiving the dhcp packets from the relay.

 

If the dhcp relay is the default gateway for the subnet with issues and you have connectivity between the core and access switches, it is required to confirm where the dhcp packets are getting dropped.

 

Regards,

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

Hello,

 


@HDawood wrote:

 

some users which connected to switch A and are in the same subnet are able to take from the DHCP pool and some not ,

 


 

Is there any known differences in equipment between users?

One known issue is that Apple devices and Windows devices use DHCP in a different manner.

 

HTH

Thx

Alex

 

 

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

@HDawood wrote: 

 

Is there any known differences in equipment between users? => for switch A if operating a pure L2, none

One known issue is that Apple devices and Windows devices use DHCP  => this is handled by relay agent and/or DHCP Server

 

BTW, have you checked that the DHCP Scope on your DHCP Server is large enough to provide enough IP address for all of your devices?  I assume if you hard code an IP address on any clients/devices in proper subnet, that the device then works fine?

 

I believe your situation has nothing to do with L2 switch unless DHCP Snooping is enabled.  I would suggest you turn off all port level security options (DHCP Snooping, IPSG. etc.) and see if this helps.  This would at minimum narrow down where to look.

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

I tried all your suggestion , unfortunately still didn't work and there is no configuration missing but there is a notice.

that this switch can see the core from show lldp neighbors command, but the core can't see it and  the core see other connected switches.

When trying to ping from each other  the ping fails.

So, How can this happen !

this switch which called A is Cisco switch.

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

Hi Dawood,

 

I would suggest you to run the following command and check whether the packets are sent/received via that interface connected to Cisco Switch - user@host> monitor traffic interface <int-name.unit-num> no-resolve size 1500

 

Check for any errors on that particular interface - show interface <int-name.unit-num> extensive | match errors  <<< Run 3-4 times



Thanks,
π00bm@$t€®.
Please, Mark My Solution Accepted if it Helped, Kudos are Appreciated too!!!
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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

I'd suggest you replace the Cisco with a Juniper switch and then see what happens 😁😁😁

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

a week ago

till that happens I shall Operate and reach the main reason for that ..

as it isn't the only Cisco switch I have and no problems with others ..

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Ethernet Switching

Re: PC isn't able to take DHCP configuration

Tuesday

Can you try to be more specific with your configuration/layout including configuration snippets from both Juniper and Cisco equipment?

 

We need to know which port(s) on the EX9204 connects to the Cisco switch, dhcp config etc.

At the same time; information about which ports works on the cisco switch and switch doesn't

 

I suspect something is not configured correctly on the Cisco switch as this is the only one having issues.

 


--
Best regards,

Jonas Hauge Klingenberg
Juniper Ambassador & Technology Architect, SEC DATACOM A/S (Denmark)
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