IP Address information

Our new leased line has gone live and our ISP has given us this information which has confused me a bit:
----
IP address: xxx.xxx.xxx..23/26 � xxx.xxx.xxx.25/26

Gateway address:xxx.xxx.xxx.2

Subnet Mask: 255.255.255.192 (this bit I understand - linked to /26 above)

Example

Firewall IP address: xxx.xxx.xxx.23
Subnet Mask: 255.255.255.192

1 usable IP xxx.xxx.xxx.24
---

Does that mean we've been assigned 3 static IP address (.23 to .25)?

Why would we want the firewall to have its own public address? Our IT department will be reconfiguring things but I'd like to understand what we've been given.

Edited by Andrue (Tue 11-Jun-13 18:28:15)

It's pretty normal for a firewall to have its own public IP address - or even more than one.

Let the router do what it's good at; routing. Let the firewall handle NAT and PAT. That needs a real IP address on the firewall external interface.

I wouldn't use a router to do NAT if I had perfectly good hardware firewalls available (which I do )

I think the best thing to do is contact the ISP again and get them to confirm exactly how many usable IP addresses you have and which one should be used by the router.

Good luck!

In reply to a post by caffn8me:

It's pretty normal for a firewall to have its own public IP address - or even more than one.

That makes sense but I'm just wondering about the extra public address in the example? Why refer to that as '1 usable IP Address'? Wouldn't the firewall address be the one you'd normally use?

I'm sure our IT guys will figure it out but I like to know what's going on as well

I'm a bit puzzled as to their address allocaton which is why I suggested clarifying it with them.

The broadcast and network addresses of that netblock fall outside the range of IP addresses you have been given so you don't need to worry abouit those eating into you allocation.

If there are three allocated addresses, x.x.x.23-25, with x.x.x.25 as the router and x.x.x.23 as the firewall that would leave just one IP address spare - x.x.x.24. Maybe that's what they mean.

That could be used for an externally facing server which you didn't want to use NAT on or added to the firewall so you could run two servers with the same protocol on different addresses with NAT.

I still think a call to the ISP is needed to make sure everyone is clear on what's what.

In reply to a post by caffn8me:

I still think a call to the ISP is needed to make sure everyone is clear on what's what.

Yeah, I'll see how our IT deal with it. We are part of a large multi-national so it's probably obvious to them what it all means

In reply to a post by Andrue:

We are part of a large multi-national

In which case you would probably want your firewalls to have real external IP addresses to set up site to site VPNs for secure data sharing

In reply to a post by caffn8me:

In reply to a post by Andrue:

We are part of a large multi-national

In which case you would probably want your firewalls to have real external IP addresses to set up site to site VPNs for secure data sharing

Ah ha! Yes. We will

funny way to express it - /26 is a large allocation with 62 useable addresses ! yet they seem to have given you three addresses.

a /30 would go from .20 to .23 or .24 to .27
/31 from .22 to .23 or .24 to .25

the /26 means that you and other customers are defined in the same block.

In reply to a post by yarwell:

funny way to express it - /26 is a large allocation with 62 useable addresses ! yet they seem to have given you three addresses.

a /30 would go from .20 to .23 or .24 to .27
/31 from .22 to .23 or .24 to .25

the /26 means that you and other customers are defined in the same block.

It might be because we've gone into this with several other businesses on the site. In effect they are providing a service to the office park then parcelling it out to us. 62 addresses still seems a bit much though - there's only 8 businesses on site.

62 would be about right for 8 businesses at approx 8 each - like some ISPs give out to end users.

If you've got a web server, mail server, remote desktop, VoIP, etc etc on fixed IPs it soon mounts up.