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Multiple IP Addresses

devnull
Newbie
Posts: 2
Registered: ‎19-09-2008

Multiple IP Addresses

Hi, I've just got a block of IP addresses and they have come designated as below, so the question is why have 3 of them got particular designations and what do they mean.
I had expected to give the router the .0 address and use the rest for my other equipment, the info below suggests otherwise, so any help appreciated.
213.229.52.0  Gateway Address 
213.229.52.1  address for router
213.229.52.2 spare address
213.229.52.3 spare address
213.229.52.4 spare address
213.229.52.5 spare address
213.229.52.6 spare address
213.229.52.7 Broadcast Address

17 REPLIES
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Multiple IP Addresses

You need to give the router the .1 address - that should be issued if you set it to get IP automatically. .0 and .7 are reserved for complex technical reasons that are explained better than I could on the ubuntu site here (scroll down the page a bit to find the relevant ones), but they can't be assigned to anything unfortunately.
MickKi
Grafter
Posts: 543
Registered: ‎30-09-2007

Re: Multiple IP Addresses

Your router has its own IP address in the cluster you were given, that's A.B.C.1.  (I'm using A, B, C so as not to tempt malicious readers from port scanning your addresses for a laugh)
Each computer or NIC in your block of addresses will need to be configured with a fixed IP address, i.e. A.B.C.1 to A.B.C.6 and each NIC will need to be configured with a gateway - which your ISP tells you is A.B.C.0.  They will all also need a broadcast address for your Class C network of 7 addresses - that will be A.B.C.7 - so that computers within the subnet can talk to each other.  Your router's address counts as a used address I'm afraid.
Does this make some sense, or shall I try harder?
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

If you have a adsl modem only (no router) running in bridge mode to a hub with 2 PC's and a router attached do these need to connect using PPPoE and each be allocated a static IP from the allocated pool?
Community Veteran
Posts: 14,469
Registered: ‎30-07-2007

Re: Multiple IP Addresses

Itsme,
Your ADSL modem will still be given the .1 address (or whatever the 2nd IP of your IP block is). It still needs to connect using PPPoA. Once connected, the other IPs in your block are automatically routed by PlusNet to your ADSL connection, you don't have to do anything your end to see them. You just allocate them to any internal PC and that PC is then accessible from the internet using that IP.
A Warning... You should have some very good firewall software running on any PC that is publicly accessible. If that PC was ever compromised, they could then gain access to your internal network or use the PC for spamming bots.
I would recommend you use a router in this situation that supports multiple IPs where you can restrict access on each of the public IPs to those ports that you only want to get through to the PC. Not all home based routers work on multiple IPs so check before buying / installing. e.g the netgear DG834 range does not work with multiple IPs.
devnull,
I suggest you edit your post to remove your real IPs and replace with ficticious ones (A.B.C.X etc) as this is a PUBLIC forum so anyone can see those IPs and thus can spam / DoS attack them.
Community Veteran
Posts: 1,576
Thanks: 3
Registered: ‎13-04-2007

Re: Multiple IP Addresses

Why do you need all these Ip's? The fact you need to ask about it suggests you may not understand the implications. 99% of servers etc can all be done from one IP and port forwarding and a lot more secure.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

With the modem in bridge mode it only sync with the exchange (PPPoA) and passes all traffic over, currently to a router. The router is configured PPPoE with PN username and password and is given my static IP. If I place a hub between the modem and router and connect 2 more PC's to the hub will these have to use PPPoE and be given different IP from the static allocation?  
MickKi
Grafter
Posts: 543
Registered: ‎30-09-2007

Re: Multiple IP Addresses

No.  Authentication on the ISP's network happens only once, by the router.  What Peter describes is not a proper (transparent) modem, but a 1:1 NAT router - some manufactures erroneously call them modems.  These operate in half-bridge mode as opposed to the full bridge transparent ATM encapsulation that you describe.
You will need to set up the multiple ip routing at the router - but you will need a more sophisticated router like e.g. Draytek which are capable of multiple NAT configurations.  A hub does not route, just passes on electrical signals (packets) without processing them.  That's why it is also called a repeater.
HTH.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

It's the NAT's that I want to lose. If I go down the route for multiple IP's it will be so a  VoIP phone would have it's own IP so that I don't have to worry about NAT proxy or port forwarding. Especially since Gradwell are having problems at their end with these but not with devices with public addressess.
The other option is that I can use the modem in routed bridge mode and it will do the authentication. I did run it in this mode for a couple of days but found that if it did lost the connection it resync'ed with the exchange but needed a kick from me to do the authentication. Which is no good when you are running a web and email server
Community Veteran
Posts: 1,136
Thanks: 2
Registered: ‎30-07-2007

Re: Multiple IP Addresses

My IP block configuration runs something like this
DSLAM --> Netgear running in bridged mode ---> xxx.xxx.xxx.213 (my 'router' ip)
xxx.xxx.xxx.213 then routes the traffic (in the true sense of the term) to xxx.xxx.xxx.212 and xxx.xxx.xxx.214
xxx.xxx.xxx.215 is the broadcast address and is useless to me as a public address.
internally I have 10.0.1.1 as my router IP which accepts and deals with traffic for xxx.xxx.xxx.213.
Internally I have 10.0.1.2 and 10.0.1.3 for xxx.xxx.xxx.212 and xxx.xxx.xxx.214 which the router directs requests to.
All traffic that comes in via xxx.xxx.xxx.213 is firewalled at that point, so a request on port 3306 (and many, many others!) to any address is rejected by the gateway with out the internal machines needing their own firewall
On the gateway I have static routes set up such that xxx.xxx.xxx.212 goes to 10.0.1.2 and bypasses the NAT tables, and the converse works so that xxx.xxx.xxx.212 & xxx.xxx.xxx.214 route through 213 and their requests are seen as their external addresses.
The real world example of this is that I run a https/imaps/smtps (SSL certificated) server on one of the addresses, on the other I have a sshd server (works great for puttying to my systems through any web proxy) and on the router ip the connection is just dropped.
I do have a FreeBSD server running the whole show for me and it works great.
As for your Gradwell specific problems .. I guess I could have a word with Peter (we went to uni together, but I doubt he remembers me) and suggest how he can run his show Wink

I think I had a point at the start of this post, but its late, I'm tired and I'm not sure I remember what it was
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devnull
Newbie
Posts: 2
Registered: ‎19-09-2008

Re: Multiple IP Addresses

  Smiley Thank you for all your helpful posts, knowing that my block of 8 is really 6 was the key info I needed so I don't waste time trying to use them.
As  I have several devices which need to use the same incoming ports then port forwarding was not going to work for me. And as regard to security, people scanning the IPs given would not cause me concern as  they were edited  before posting, but thanks for mentioning it as it wasn't obvious.
Having just joined PlusNet I have been  impressed by the automation on the website and the quality and speed of their tech support. I phoned about a tech issue at the start and the person who answered actually knew what they were doing and provided an accurate and comprehensive response, which is unusual in this business, and the e-mail support is quick too. My benchmark for support is Positive Internet who provide web hosting and they have very good support and very fast responses, but Plusnet is proving very close.
It's also great to find these forums with helpful and knowledgable people keen to help, so while I hope all goes smoothly now, if not, I'll be back.

MickKi
Grafter
Posts: 543
Registered: ‎30-09-2007

Re: Multiple IP Addresses

Quote from: itsme
It's the NAT's that I want to lose.

You can't lose NAT and have routing to more than one boxen.  Who's gonna tell the packets, which are destined for different IP addresses, where to go after they leave the modem? (a modem is only dealing with the atm link - in simple terms of course).
Quote from: itsme
If I go down the route for multiple IP's it will be so a  VoIP phone would have it's own IP so that I don't have to worry about NAT proxy or port forwarding. Especially since Gradwell are having problems at their end with these but not with devices with public addressess.

I am not familiar with VoIP or Gradwell devices, but essentially port forwarding works if the device in question is using a known protocol and static ports.  Devices or applications that open random ports cannot be dealt with by port forwarding.
Quote from: itsme
The other option is that I can use the modem in routed bridge mode and it will do the authentication. I did run it in this mode for a couple of days but found that if it did lost the connection it resync'ed with the exchange but needed a kick from me to do the authentication.

Do you mean this physically?  Shocked
What did you have to do?  Some half-bridge modem implementations are a tad ropy.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

I'm using a Netgear DM111 ethernet modem.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

@mickKi
Have a read of this from another Plusnet user and for the Linux server I would have my VoIP adaptor and when I previous mentioned a hub it is in fact a switched hub.
itsme
Grafter
Posts: 5,924
Thanks: 1
Registered: ‎07-04-2007

Re: Multiple IP Addresses

If I go down this route I now know how to setup my router to bypass the NAT and assign another public address . I'm using a Linksys router running dd-wrt open source firmware.
Quote
VLAN Bridging WAN and a LAN port
From DD-WRT Wiki
Jump to: navigation, search
For WRT54GS v2
If your ISP gives you multiple public IPs, and you want to hang a second router or other device on your main router with direct access to the WAN, fear not, it's easy:
Your original VLAN should look like this (among other lines) if you run the command nvram show |grep vlan
vlan0ports=1 2 3 4 5*
vlan1ports=0 5
So the following commands move LAN port 1 to the WAN VLAN:
nvram set vlan0ports="2 3 4 5*"
nvram set vlan1ports="0 1 5"       
nvram commit
reboot
That's it. No firewall rules or bridging needs to be set up. Port 1 is now a direct WAN port, and your second router/AP/server can use one of your extra public IPs.

To undo this, make a note of that the values were for vlan0ports and vlan1ports before changing them.