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Author Topic: DSR-250 routing possibilities question  (Read 3901 times)

sudderlea

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DSR-250 routing possibilities question
« on: December 01, 2016, 06:21:41 AM »

Hello, all,

The US support sent me to my national support with my simple question. My national support in turn doesn't even take the effort to answer it. So I hope to obtain an answer, before bying a DSR-250, to it by posting it here. I don't see it answered in detail in the user guide. The question :

From my ISP, I receive a 192.168.128.x WAN address (from an ISP- provided router which basically provides 254 devices with an IP adress). Apart from connecting my router to it, I want to avoid using that WAN side, as I don't have any control whatsoever over that router and its WAN side. So I cannot get around the 192.168.128.x WAN side address limitation.

My LAN side has 5 subnets which fit in a 192.168.0.x netmask 255.255.128.0 address range : 192.168.1.x, 192.168.10.x, 192.168.20.x, 192.168.30.x and 192.1168.40.x.

This means that the DSR-250, if I buy one, should be able to route (and preferably also DHCP- serve) a 192.168.0.x netmask 255.255.128.0 network.

Can it do so ? Or is the "best" netmask offered 255.255.255.0, like it is in that recently baught (and returned) router (and where the user guide didn't specify that limitation either) ?

Thanks in advance !
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FurryNutz

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Re: DSR-250 routing possibilities question
« Reply #1 on: December 05, 2016, 06:40:58 AM »

Link>Welcome!

  • What region are you located?

When you contacted your regional D-Link support office did you phone contact them first?

Not much experience with DSR routers. D-Link support should be able to answer this. If the 250 doesn't, maybe the 500 or 1000 series does.

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sudderlea

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Re: DSR-250 routing possibilities question
« Reply #2 on: December 05, 2016, 07:47:34 AM »

Belgium. But apart from an email address (they're not even responding to my email), they seem to make finding a telephone number as difficult as possible : the first and only thing you get, after pressing the "contact" button, is a page with FAQ's (not answering my specific question, only some very easy-to-find user manual questions). And there it stops. So I thought to be more lucky to ask it here...
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FurryNutz

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Re: DSR-250 routing possibilities question
« Reply #3 on: December 05, 2016, 08:05:17 AM »

I'll have someone I know here take a look. Not sure if he can help...

Ya I don't see a phone number for your region, only email be-info@dlink.com

You might try Germany instead and see if they can point you to your regoinal number:
http://www.dlink.com/de/de/contact-d-link
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PacketTracer

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Re: DSR-250 routing possibilities question
« Reply #4 on: December 06, 2016, 05:17:21 AM »

Hi,

just thought a bit about your problem. First let me summarize my understanding:

Your DSR-250 (to be bought in the future) shall handle:

  • 1 WAN address 192.168.128.x/24 from the aggregated block 192.168.128.0/17, where 192.168.128.0/24 is your ISP's WAN network encompassing up to 253 CPE's WAN interfaces and the ISP's router interface
  • 5 LAN networks 192.168.L.0/24 from the aggregated block 192.168.0.0/17 where L is one of {1,10,20,30,40}

Considering routing (DSR-250 "only" has to handle 6 explicit networks of size /24 and a default route to your ISP's router) and DHCP (you have to create 5 DHCP pools defining subsets out of /24 ranges for you LANs), I do not see any obvious case, where the DSR should have to handle one of the aggregates 192.168.0.0/17 or 192.168.128.0/17. But maybe I misunderstood your scenario.

But I do agree (while I cannot confirm this to be true for the DSR-250):
  • A router should allow the configuration of interface addresses with any prefix length, not just prefix lengths that are a multiple of 8!
  • A router should allow the definition of routes to destination IP ranges of any size (=any prefix length)!
  • A DHCP server should allow the definition of IP pools of any size, not just ranges with prefix lengths that are restricted to multiples of 8!

<EDIT>
Your statement "My LAN side has 5 subnets which fit in a 192.168.0.x netmask 255.255.128.0 address range : 192.168.1.x, 192.168.10.x, 192.168.20.x, 192.168.30.x and 192.1168.40.x." drives me to the assumption that you possibly might have a wrong picture of networking. In fact 192.168.1.0/255.255.128.0, 192.168.10.0/255.255.128.0, 192.168.20.0/255.255.128.0, 192.168.30.0/255.255.128.0 and 192.168.40.0/255.255.128.0 are useless, because using mask 255.255.128.0 reduces these "five" networks to the same single network 192.168.0.0/255.255.128.0.

Instead you have to form the 5 networks using mask 255.255.255.0: 192.168.1.0/255.255.255.0, 192.168.10.0/255.255.255.0, 192.168.20.0/255.255.255.0, 192.168.30.0/255.255.255.0 and 192.168.40.0/255.255.255.0. These 5 networks can be seen to stem from the aggregated block 192.168.0.0/255.255.128.0. And this could  be the block, your ISP could route to your DSR (as a route defined in the ISP's router), giving you the freedom to define up to 128 LAN networks of size 255.255.255.0
</EDIT>

PT
« Last Edit: December 06, 2016, 05:54:49 AM by PacketTracer »
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sudderlea

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Re: DSR-250 routing possibilities question
« Reply #5 on: December 06, 2016, 10:55:16 AM »

Hello,

Thank you for your response. I may have used the word "subnet" improperly. But if I would have correctly specified what I mean, I think I should have "just" used the word "internal network" as meaning "my LAN side", not mentioning anything like a "subnet". In my internal network, I have a 1GBit switch. All of my (own) devices are connected to it, and I'd want my DSR not to have to intervene for routing network traffic between devices in my LAN.

On the other hand, that switch can't route any of my 5 "subnets" if they'd have a netmask 255.255.255.0. Hence, I'd want to avoid using 5 "subnets" with a netmask 255.255.255.0 : I would rather use one single internal network with a netmask 255.255.128.0, so that I don't need my DSR to intervene for routing between these 5 "subnets". I would only want the DSR routing packets coming from my internal network on their way to and from the internet. If I would have 5 "subnets" with a netmask of 255.255.255.0, all my internal network traffic would have to be routed in between them by my DSR. I would want to avoid this (I got to know the word "router on a stick", and I think that would be the case then).

To make my long story short : I may misunderstand your question completely, but it is my perception that if I'd have 5 255.255.255.0 "subnets", all internal network routing would have to pass via the DSR. Maybe that's not correct ? And if possible at all, also my DHCP server should (therefor) be capable of setting the served NIC's netmasks to 255.255.128.0 (and not 255.255.255.0) ?
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PacketTracer

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Re: DSR-250 routing possibilities question
« Reply #6 on: December 07, 2016, 03:34:33 AM »

Hi again,

well, sorry for my misunderstanding.

To put it simply, all you want is to have a single, flat (but huge) LAN network 192.168.0.0/17, where the DSR LAN interface and all devices can potentially use one out of 32766 addresses (192.168.0.1/17 - 192.168.127.254/17). But for some reason, this address space shall be a bit structured in that there are obviously 5 groups of devices, that shall use addresses out of ranges 192.168.X.0-192.168.X.255 where X is one of {1,10,20,30,40} (yes, and of course all with mask /17 = 255.255.128.0.0!).

This requires the DSR LAN interface configration to accept a mask /17 for one address out of 192.168.0.1 - 192.168.127.254 that you will select to be the default gateway for your LAN devices. Apart from the question if this is possible with a DSR (it should!), the more demanding part is if the DSR shall also work as a DHCP server for your LAN. In this case you would have to define a DHCP pool that is not contiguous but consists of chunks of the above mentioned 5 subranges (taken this alone there is a good chance, that this is not supported by DSR); and you have to ensure, that any device gets an address out of that subrange that you have reserved for use by the group of devices, that the device under consideration belongs to. You usually do this by configuring DHCP reservations (for all devices!) that assign fixed IP addresses depending on the devices' MAC addresses.

Looks like you actually want to have a structured network, but don't want to establish the technique that is normally used to do so: Forming subnets of adequate sizes (for simplicity in your case: networks of size /24) eventually based on VLANs and connecting them via routers or possibly firewalling routers to enforce traffic control (isn't this the underlying reason for your 5 IP subranges/device groups?).

To do so and to prevent DSR from routing LAN internal traffic (you don't want that for some reason), you would have to provide at least one internal (possibly firewalling) router that connects your 5 subnets of size /24 and a 6th uplink network (for simplicity also of size /24) to your DSR. Say, you use uplink network 192.168.127.0/24, 192.168.127.1/24 for DSR's LAN interface and 192.168.127.254/24 for the internal router's uplink interface, all you would have to do at DSR is to configure a route for 192.168.0.0/17 with next hop 192.168.127.254. To become even more independent of the DSR (or an even simpler internet router - "router on a stick") you should also operate an internal DHCP server placed somewhere in the network (possibly on your internal router or firewall appliance), where its configuration is even simpler then, because you would have to configure 5 pools for real networks (and without DHCP reservations) only - a standard DHCP scenario.

Think about it ...

PT
« Last Edit: December 07, 2016, 03:39:56 AM by PacketTracer »
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sudderlea

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Re: DSR-250 routing possibilities question
« Reply #7 on: December 07, 2016, 11:58:43 AM »

My goal is to replace my current Linux NAT-ting, firewalling, DHCP serving router by a new "real", as much as possible maintenance-free "real" NAT-ting, firewalling, DHCP serving router.

With this obsolescent Linux router, I route all inter-subnet LAN traffic via that Linux router (its LAN- side NIC has 5 IP addresses, one per "real" subnet). In the near future, I want to avoid this same situation because of perfomance reasons : all LAN devices should not get routed their inter-subnet-packets via the router any longer, because that implies that I share one single GBit interface for all inter-subnet and internet traffic. That way, two devices in different subnets backing up some data, at the same time as another device occupied doing a big download, and there would already be a performance penalty. Therefor, I'd rather have the "old" inter-subnet traffic done by my (in the meantime newly bought) switch. Which is the reason why I want to get rid of the 5 255.255.255.0 netmask'd subnets, and use a single 255.255.128.0 netmask as from now, not having to explicitly route the "old" inter-subnet traffic. The DHCP server serves IP addresses based upon all my device's (known) MAC addresses, denying any IP address to unknown devices. It should therefor, as from now, be able to provide a netmask 255.255.128.0.

So that "standard" setup which I used before would be replaced by my NAT-ting, firewalling, DHCP serving router, and my 5 255.255.255.0- netmasked subnets would be replaced by one single 255.255.128.0 internal network;

I understand that it may look to be some weird, unusual kind of network setup, but this wouldn't bother me too much, provided I have the router serving IP addresses with a netmask of 255.255.128.0, having all internal LAN work be done by my switch, and only the internet traffic passing through my "new-to-be-bought" router.

So that's why  really would like to know if the DSR-250 can do this. Even if I could have the DHCP server functions done by some RaspberryPI, still then, I'd strongly prefer to have these DHCP functions done by the router as well.
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sudderlea

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Re: DSR-250 routing possibilities question
« Reply #8 on: December 08, 2016, 04:48:53 AM »

Thanks to everyone having answered and having made the effort to try to answer my question. As I didn't receive any answer from neither D-Link US nor from my national D-Link "support" (they didn't even make the effort to answer my simple mail), I suppose that the DSR-250 can NOT route NOR DHCP- serve IP addresses with a /17 netmask.

Moreover, it frustrates me even more that most routers which I've looked up make it hard to find out whether they route and/or DHCP serve /17 netmasks. I was determined not to be fooled a second time (right before asking this question I had just returned a router which didn't specify that limitation either). But then again I had a hard time to get, black-on-white, the confirmation of the possibility to route or DHCP serve such a simple setup as mine is. To my feeling, this should be specified if not in the datasheets, then still it should be specified in the user manuals !!! What else IS important for a router than to mention it's ... routing capabilities ??

This said, for my part this thread can be closed, as it is (at least not any more for me) not any longer of any use, as I bought Ubiquity's ERLite-3, which DOES enable to as well route, as well DHCP serve /17 networks. For even a very affordable price.
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FurryNutz

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Re: DSR-250 routing possibilities question
« Reply #9 on: December 08, 2016, 06:26:51 AM »

I recommend phone contacting support always. Usually email only support basic support information and not of any use for more advanced needs.

Glad you found something that works for you.

Enjoy.  ;)
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