Fios and static ip address config

[azev]

I worked on setting up a small office for a colleague of mine this weekend and found out something pretty interesting. He got fios business installed with static ip address.
When I got to his place, I saw a laptop jacked in directly from the fios ONT and a static ip address of x.x.x.90/24 with .1 as gateway... According to the verizon paperwork the block of ip assigned to him are .90-94

I found this kind of surprising; I am used to getting assigned ip address by using proper subnetting. This is the first time I've seen static ip address assigned like this.
Just for kicks, I wonder if I can use different ip address out of my range; so I changed the ip address of the laptop to 89 and 95, but with both ip I cant get the laptop to ping the outside world.

I am curious as to how they did this? (my initial though is some sort of access-list with ONT MAC Address restriction) Any other theory are welcome

Is this a good accepted/common method of ip address conservation ?

 

[spidey07]

It's so they can summarize that range and other customers without wasting address space on a ton of /28 /29s. It's common.

 

[ScottMac]

The data is tunneled, an access list of sorts, more like policy-based-routing, determines valid traffic for that tunnel. It's an Alcatel thing.

 

[azev]

Originally posted by: spidey07
It's so they can summarize that range and other customers without wasting address space on a ton of /28 /29s. It's common.

ic.... I understand the technology and concept, just never put it in action.
At every place I ever worked even a tier 2 provider, they are handing out ip with the common subnetting /29 all the way to /18.

 

[drebo]

That's how lots of places do it, and for point-to-point connections, it's the easiest. But, this is something I see done frequently with things like "business ethernet" or bonded SDSL. It's not a bad way to do it, necessarily, as the ISP gets to conserve IPs and can hand them out as needed.

 

[shaitand]

@ScottMac

I know this thread is old but I'm waiting for the installer to arrive for my "/29" today. I'm not familiar with the "Alcatel thing" so maybe they are taking care of this somehow. Otherwise this sounds like a recipe for nefarious arp games. This would put everyone with addresses on that /24 block in the same broadcast domain meaning anyone in that block could sniff the broadcasted arp packets. Even if the FIOS side acl restricts to the right destination MAC preventing you from poisoning the cache with gratuitous arps the broadcast packets would tell you everyone's MAC addresses which you could then just spoof and you might even still be able to use cache poisoning to effectively DOS them.