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Public IP

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Public IP

Trying to work out if Plusnet support the setup I need.  After speaking to Plusnet, they recommended that I should use the fourms to ask questions about my account, so here I am (absolutely cracking business support, 1/10).  I've illustrated the setup I want to achieve below.  My question is, I want a /30 behind my router, which goes to my firewall (a standard business network setup).  Then I'll need a public IP on my router's WAN interface.  Simple stuff, but Plusnet haven't got a scooby doo what I'm on about.  Do they support this, and if so what special words do I need to use to communicate in a way they understand.

 

LAN  ------  Firewall ------i want a /30 here-------Router--/32 Public IP--------------ISP

17 REPLIES 17
Anonymous
Not applicable

Re: Public IP

@sg4rb0sss - First off I’m not a business service user, but like Plusnet support I’m confused as to your requirements. If you’re wanting a /30 subnet then you can apply that to the router’s LAN interface.

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

Correct. However for it to be publically routable, you need the ISP to route the public /30 via the /32,

Anonymous
Not applicable

Re: Public IP

What do you mean by publically routable? If you're wanting the devices on the /30 to be accessible from the internet then put the /30 LAN in a DMZ.

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

Yes, the /30 should ideally be on the firewall, which is what I've drawn.  Plusnet inform me, that getting a /30 works is that they can only provide a /30 on the WAN side of my connection (i.e. where I have shown in my post, where the /32 is).  That is exactly what I don't need.

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

I meant to write, "the way that getting a /30 works is, "

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

Mook, let me get you thinking about this properly ok, because you don't appear to fully understand the problem. If Plusnet provide me a public /30, and I configure it on my firewall, that's fine okay.  When I configure the PPP session on the router, Plusnet have then informed me that I would need to use that public /30 on the WAN interface. 

 

Do you now see the very simple problem?

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

All I need, is what I originally asked in my first post.  And I can't understand why nobody at Plusnet seems to ever am heard of this setup.  As a network engineer whos worked both in an ISP & and branches, the setup I've asked for in my first post is how every single company I've ever helped has set this up (all be it with larger subnets).  I can't understand why Plusnet are making it difficult,

Anonymous
Not applicable

Re: Public IP

@sg4rb0sss, I’m a software engineer not a network engineer, so from your #7 post I can see the logic as to why the /30 would be applied to the WAN as you’d need an IP for your WAN and one for Plusnet’s Gateway.

Your original configuration I can easily replicate here and I don’t need Plusnet’s intervention to do it as anything on the inside of the WAN is my responsibility so doing what you want is very doable as I see it.

Also, what do you mean in #6? A /30 or .252 provides a network address, two hosts and a broadcast.

As for seeing the ‘very simple problem’, no I can’t, so as you’re the networking guy I'd appreciate an explanation of what I’m missing as I can’t see it for the forest of CAT5’s.

Taking the addressing out of it what exactly are you trying to achieve?

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

A globally routable network on the WAN interface of the ASA

Anonymous
Not applicable

Re: Public IP

Isn't that what you'd get if you used a DMZ. Maybe you could ask on the Cisco forum if you are using an ASA.

MisterW
Superuser
Superuser
Posts: 11,430
Thanks: 3,588
Fixes: 275
Registered: ‎30-07-2007

Re: Public IP

First , you need to convince PlusNet to provide you with multiple static IP's. That's getting very difficult these days. You used to raise a ticket to request it but with the ticket system being largely replaced with chat, I'm not sure how you would go about it now!.

Then you need a router that can be configured for a public routed subnet. I'd be pretty sure that the current Hub one cant do that.

 

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

legume
Rising Star
Posts: 179
Thanks: 12
Registered: ‎21-07-2013

Re: Public IP


@sg4rb0sss wrote:

Correct. However for it to be publically routable, you need the ISP to route the public /30 via the /32,


 

I don't really understand this bit, but then it's years since I had a /29 (not Plusnet) and I can't remember every detail.

Maybe you mean the ppp interface on the router gets your first IP address and shows the mask as /32?

I assume you have a proper router and not some locked down free home thing.

IIRC what I did was turn off nat/dhcp , duplicate the wan(ppp) address on the lan interface with (for you) a /30 mask (replacing the "normal" private address/subnet.

Guessing here, what you should do next is put your other public ip address with a /30 mask on the firewall wan facing nic and set it's default route to be via the address you set on the router.

I assume here that the router automagically sets its own default route to be via ppp.

Then set up nat on the firewall.

TBH it was a long time ago so above may be somewhat useless.

FWIW it was possible on Enta to use all 8 of my /29, so maybe you can have 4 rather than 2 addresses. You wouldn't be able to use the above set up to do it, though.

IIRC, just as a test, I did it using snat on the router with everything else local. Another way would be to cook up multiple /32 host routes so the addresses could live elsewhere - but that's getting away from the "proper" set up you asked for.

Edit - ugh, change some  /32s to the 30s I should have written in the first place.

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

Don't worry all.  This was a question to see if you have to ask Plusnet for something in particular to get a publically routable subnet on the inside.  Literally that's all I needed to know, the rest is easy.  I guess my answer really is, that they don't actually facilitate it.  I'll just wait for the contract to expire and renew elsewhere.

 

Thanks anyway!

sg4rb0sss
Hooked
Posts: 9
Registered: ‎31-03-2017

Re: Public IP

And Mook, no, the answer to my question about Plusnet's lack of services does not lie in the Cisco forums lol.