[BlueOnyx:14031] Re: Problem setting interface alias net mask to 255.255.255.255

[Chuck Tetlow]

>

> Sounds to me like your WSP doesn't have enough valid IP addresses. So they are creating their own in house subnets and creating their own network, similar to a 192.168.0.0 internal network.

> This may be out of line, but I suggest moving to a service provider that can offer REAL static IP addresses.

> I can imagine the traffic lag at times.

>

No,

Actually just the opposite.

When you create subnets, you loose usable real-world IPs.  You loose three IPs per subnet - the network ID, the default gateway, and the broadcast.  If you take a .24 (255.255.255.0) block and break it up into 32 networks of eight IPs each - you'll loose 96 real-world IPs (and each of those 32 networks only has five usable IPs left).  That's a HUGE loss of potential revenue!

But if you do it this way, you not only don't loose those 96 RWIPs - you also gain the ability to move IPs/sites around among your virtual hosting servers with only a change in the router's static routing table.

One of my customers has a entire 24 network, half another, and parts of a third supporting the virtual sites on eight or nine BQ and BX virtual servers.  The servers each have a IP out of a /28 network on their main interface (a separate network than the virtuals are on).  Then each site that has its own IP gets one out of those other blocks.  If I need to move/migrate sites around, I do a cmuExport on the departing server, scp to the new server, a cmuImport on the new server, and then point the traffic to the new server in the router.

I'm not saying this is a optimal solution.  But it does have advantages over using subnets.  For example - if you have the main server interface and all the virtuals in a single subnet, what do you do when you run out of IPs??  So if he had a /29 (255.255.255.248) network - he'd only have five available IPs.  One for the server, and four available for virtual sites.  So what does he do when a fifth customer is ready to come on-board (wanting a real-world IP)??  Uh Oh!  That could be a nightmare of changing all the IPs when the ISP gives him a new /28 subnet (then you also have to change the DNS for all of the existing customers, each customer has to update their apps that used IPs instead of names, etc....).  WHEW - what a nightmare!

So this way of doing it does solve a lot of problems and conserves RWIPs.  Unfortunately it does cause some other small problems.  One specifically I reported three years ago and still hasn't been fixed.  So I just manually fix the interfaces at the command line, and roll on happily.

Chuck

 
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