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Author Topic: Respond to DHCP requests on guest SSID only  (Read 13654 times)

rkjnsn

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Respond to DHCP requests on guest SSID only
« on: May 26, 2009, 11:25:59 AM »

I bought this router to replace my old Wireless-G router on my home network.  One of my motivations for choosing this router was the Guest Zone feature, to allow guests to use the Internet without me having to give them access to the local network.

On my home network, I run my own DHCP server so that I can better configure it to suite my needs.  Thus, I had the internal DHCP server disabled on my last router.

To my dismay, I discovered that disabling the DHCP server for the local network on the DIR-655 also prevents guests from obtaining an IP address automatically.

So, my question is, is there any way to leave the DHCP server enabled, but have it only respond to requests on the guest SSID?

Thank you,
Erik Jensen
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EddieZ

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Re: Respond to DHCP requests on guest SSID only
« Reply #1 on: May 26, 2009, 11:31:42 AM »

Nope. If this were to work like you suggest, the guest part would need to be completely (physically) separat from the other/main internal parts (separate radio etc). The guest feature on the DIR is enabled by ways of VLAN.

To be honest, I don't know any other home router that has the ability you are describing.
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rkjnsn

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Re: Respond to DHCP requests on guest SSID only
« Reply #2 on: May 26, 2009, 02:35:21 PM »

You're response does not make any sense to me.  By using separate VLANs, two separate, logical networks are created, and it is certainly possible to have a DHCP server only be attached to one of them (the same way computers are only attached to one, and cannot communicate with the other).  In fact, some complex network set-ups have many VLANs, with DHCP servers that serve a subset of those, using different pools for each.

Now, this is a home network that I am talking about, and I am not trying to do anything that complex.  I understand how things like having a different subnet for each, or having overlapping IP addresses would make things unnecessarily complex from a firmware's point of view.  I am not trying to do any of that.  I want it work pretty much how it does now, with both VLANs sharing a subnet, and with no IP address overlaps between the two.  The routing would work exactly the same.  The only difference would be that the built in DHCP server would only serve IP addresses on the Guest Zone.
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EddieZ

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Re: Respond to DHCP requests on guest SSID only
« Reply #3 on: May 26, 2009, 03:32:42 PM »

The answer to the question is easy: no, it does not support this feature. Whether or not this feature belongs in this router class (looking at the other standard (excl. DD-WRT, Tomato etc) routers like Linksys, Netgear) or is 'do-able' is always a yes/no discussion. In the context of your dismay, discovering that this feature is not present should not be that big a surprise. But that's my opinion and you will probably have another opinion about that.  ;)
« Last Edit: May 26, 2009, 03:36:57 PM by EddieZ »
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ttmcmurry

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Re: Respond to DHCP requests on guest SSID only
« Reply #4 on: May 26, 2009, 08:55:23 PM »

Yeah, it sounds like the feature you're requesting is DHCP relay. 

EddieZ is quite right- that's an enterprise-class feature found on high end Routers & Layer-3 Switches. 

Basically the DIR-655 is working proprly by design in that on the default vlan, the standalone DHCP server that you have will respond to DHCP broadcasts on its subnet.  The guest zone, by default, isn't routing between VLANs and thus the requests for DHCP are discarded.

What you could try is enabling the routing between zones and see if it is forwarding the DHCP requests... however it does defeat the purpose of the guest zone if isolation is what you want the zone to do.  And without having a DHCP server handy right this second I can't say much more..
« Last Edit: May 26, 2009, 08:57:10 PM by ttmcmurry »
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rkjnsn

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Re: Respond to DHCP requests on guest SSID only
« Reply #5 on: May 26, 2009, 11:53:30 PM »

EddieZ: My last post was a response to your assertion that having the built in DHCP server only respond to requests in the guest zone was technically infeasible based on the architecture of the router.  This is what doesn't make sense to me.  The importance of said feature is a separate matter.

As for whether the feature belongs in this "router class", I would first say that features vary greatly between routers.  One of the main reasons that I picked this router was that it supported various "advanced" features that it's competitors do not, such as WPA Enterprise authentication.  I have also read about other people who wanted this exact feature in a home router, so I don't think it is weird or unusual in any way.

Now, if there is a good technical reason why having the DHCP server respond to only one network is infeasible (or, equivalently, blocking traffic between the other and the DHCP server), please let me know, but your previous explanation did not jive with my previous networking experience.  Would you be able to describe why separate radios would be required in more detail? Changing which of the internal VLAN(s) the internal DHCP server binds to would seem to me to be a fairly trivial matter.

I am not trying to be a pain, I just like to understand what is going on.

ttmcmurry:  DHCP relay is not at all what I am looking for, and I agree that that would be a feature beyond the scope of this router.  I do not what the guest network to obtain addresses from the standalone DHCP, and indeed, I want the networks to be isolated from each other.  I am trying to have the guest network be served by the routers built in DHCP server, like it normally is, but at the same time be able to use my standalone DHCP server on the main network.

Thank you all,
Erik Jensen
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EddieZ

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Re: Respond to DHCP requests on guest SSID only
« Reply #6 on: May 27, 2009, 09:18:43 AM »

I am not a pure 'techie'  so I will not bother anyone with my foolish choice of words to describe what I mean  ;).

Like I said, I am not really interested in "why" the feature is isn't there. From a firmware/Ubicom platform point of view this feature can be incorporated, everything is possible. You can even let this Ubicom platformed router play MP3's /audio (True, the chipset has the feature  ;D)...

For a home router there a plenty of other features available/requested. The feature mentioned have absolutely no use for the n00b user IMHO. They are much more interested in torrent or nzb clients running on the router and might only use the feature for facilitating 'a' guest to the house, so they don't have to mess with the router setup.
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Lycan

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Re: Respond to DHCP requests on guest SSID only
« Reply #7 on: May 27, 2009, 11:55:14 AM »

EddieZ: My last post was a response to your assertion that having the built in DHCP server only respond to requests in the guest zone was technically infeasible based on the architecture of the router.  This is what doesn't make sense to me.  The importance of said feature is a separate matter.

As for whether the feature belongs in this "router class", I would first say that features vary greatly between routers.  One of the main reasons that I picked this router was that it supported various "advanced" features that it's competitors do not, such as WPA Enterprise authentication.  I have also read about other people who wanted this exact feature in a home router, so I don't think it is weird or unusual in any way.

Now, if there is a good technical reason why having the DHCP server respond to only one network is infeasible (or, equivalently, blocking traffic between the other and the DHCP server), please let me know, but your previous explanation did not jive with my previous networking experience.  Would you be able to describe why separate radios would be required in more detail? Changing which of the internal VLAN(s) the internal DHCP server binds to would seem to me to be a fairly trivial matter.

I am not trying to be a pain, I just like to understand what is going on.

ttmcmurry:  DHCP relay is not at all what I am looking for, and I agree that that would be a feature beyond the scope of this router.  I do not what the guest network to obtain addresses from the standalone DHCP, and indeed, I want the networks to be isolated from each other.  I am trying to have the guest network be served by the routers built in DHCP server, like it normally is, but at the same time be able to use my standalone DHCP server on the main network.

Thank you all,
Erik Jensen

It's not included beacause of the memory requirements of maintaining a second DHCP client list as well as a second statetable for the NAT.
And because we said so. :)
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rkjnsn

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Re: Respond to DHCP requests on guest SSID only
« Reply #8 on: May 30, 2009, 01:13:41 AM »

Lycan:  I appreciate your response.  However, it would appear that you have misunderstood what I am asking for, as what I am asking for would neither require a separate client list nor a second state table.  I am not asking to have a second DHCP server. All I want to be able to do is control which network(s) the single already existing DHCP server responds to.

There would not be a second DHCP client list, as there would still only be one DHCP server and configuration, and there would not need to be a second NAT state table as both networks would have the same subnet, with no shared IP addresses, just as it is now.  From a NAT/routing perspective, nothing would change.  The only difference would be that the DHCP server would only bind to one of the two VLANs.

Again, thank you for your response.
-- Erik Jensen
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EddieZ

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Re: Respond to DHCP requests on guest SSID only
« Reply #9 on: May 30, 2009, 01:40:28 AM »

Not 100% sure, but it still sounds like you need the things Lycan mentioned in order to create the seperate binding.
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Lycan

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Re: Respond to DHCP requests on guest SSID only
« Reply #10 on: June 01, 2009, 12:00:35 PM »

Ahhhh,
I understand your request a little more clearly now, so I'll fail over to my second statement. Because we said so.

Sorry. That level of programming and added functionality for a product that's on it's wayout is HIGHLY unlikely, esp. when you consider the BASIC features that this model lacks that would have broader appeal like LAN side routing or WDS.

Just saying.

That being said I'm going to end this thread. It's reached the end of it's usefulness.

-Lycan

P.S. awesome chatting with you, if you feel like you still have something to add, PM me and I'll unlock the thread.
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