Wireless Access

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Contributor II
Posts: 70
Registered: ‎05-01-2015

How RAP's internal DHCP server works in Bridge Mode?

Hi Guys, I have a doubt about RAP's internal DHCP server in Bridge Mode. In the 6.4 user guide, I see that "Configuring the DHCP Server on the Remote AP" is possible only for bridge backup SSID, if the controller is unreachable. I was testing in my lab and I noticed that when I set the forward mode to "bridge" and RAP operational mode to "standard" and specify the vlan-id for "Remote-AP DHCP Server VLAN" in the ap-system-profile(same as the vlan-id in the VAP), the wireless users are getting an IP address from the ap-system-profile scope of the RAP rather than the local DHCP server. However, if I remove the vlan from the "Remote-AP DHCP Server VLAN" of the ap-system-profile, the same wireless clients are getting an IP address from the local DHCP server present at the remote site. Having said that, could you please confirm if it's a Bug in the code? or is it lack of documentation in the User guide as it says that it supports only in backup SSID?
Guru Elite
Posts: 21,279
Registered: ‎03-29-2007

Re: How RAP's internal DHCP server works in Bridge Mode?

If the Remote AP DHCP server VLAN matches the VLAN ID for the RAP, bridged clients that are placed in the same VLAN  will be offered an ip address.  The VLAN number is never really removed.  You need to check on the commandline it could be "1" (show ap system-profile).

 

There are many ways to configure this that are Valid and I want to suggest the way that benefits you.  What are you trying to do?

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How RAP's internal DHCP server works in Bridge Mode?

[ Edited ]

Hi Colin,

 

Thank you for your post. Yes, I understand that when the Vlan ID in the VAP matches with the Remote AP DHCP server VLAN, is when the Bridge/Backup users would get an IP address from the RAP's internal DHCP server.


However, my concern is even when the forward/operation mode is set to Bridge/Standard or Bridge/Persistent or Bridge/Always I notice users are getting an IP address from the RAP's internal DHCP server.


Is it possible for both the servers to Offer an IP address in the above mentioned forward/operation modes.

 

So my question is:-

1. Is that an expected behaviour? because the UserGuide says that RAP's internal DHCP will work only for Bridge/Backup SSID only.

 

Bridge Standard.png

Attached is a screen-shot of my Lab setup

      1. We have two SSID's( SSID1 and SSID2) both set to Bridge/Standard mode.
      2. The Wifi-client1 connects to SSID1 and the Wifi-client2 connects to SSID2.
      3. I notice based on the wireshark captures of the client that the Wificlient1 gets DHCP Offer from the           RAP's internal DHCP server as well as from the Local DHCP on the Switch.
      4. But the Wificlient2 gets DHCP Offer only from the Local DHCP on the Siwtch.
      5. The only thing that is different is that we have specified vlan20 as the "Remote-AP DHCP Server             VLAN"
      6. However, the UserGuide says "Remote-AP DHCP Server VLAN" --> VLAN ID of the remote AP               DHCP server used if the controller is unavailable. This VLAN enables the DHCP server
          on the AP (also known as the remote AP DHCP server VLAN). If you enter the native VLAN ID,               the DHCP server is unavailable.


My next question is:-

2. So what happens if the Controller is available and if I enter the "Remote-AP DHCP Server VLAN", does it still enable the DHCP server on the AP?

Guru Elite
Posts: 21,279
Registered: ‎03-29-2007

Re: How RAP's internal DHCP server works in Bridge Mode?

The user role acls also play a role in what happens to client traffic. Again, I don't want to go through iterations of configurations that you are not interested in. It would be easier to describe what you are interested in doing and I can say if it works and if so, how you can do it.


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How RAP's internal DHCP server works in Bridge Mode?

Hi Colin,

I think you have misunderstood my question. To put it straight, my only doubt is, Is it expected for the "Remote-AP DHCP Server" which is in the ap-system-profile to work in Bridge/Standard or Bridge/Always or in Bridge/Persistent apart from Bridge/Backup?

Valued Contributor II
Posts: 804
Registered: ‎12-01-2014

Re: How RAP's internal DHCP server works in Bridge Mode?

Hi,

 

The purpose of RAP internal DHCP is to work on Bridge mode with any operation mode ( Always, Persistent and Standard) along with Backup.

 

You need to configure the VLAN properly.

 

Please feel free for any further help on this.

Cheers,
Venu Puduchery,
[Is my post helped you ? Give Kudos :) ]
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How RAP's internal DHCP server works in Bridge Mode?

Hi Venu, Thank you for your spontaneous response. That answers my question.

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