WTH? Class A IP using subnet mask 255.255.255.255?

[JackBurton]

I'm using a PPPoE connection for ADSL. When I do an IP config /all, I get an IP for my PPP adapter:

IP 64.X.X.X
subnet 255.255.255.255
gateway "same as IP"
primary DNS "fine"
secondary DNS "fine"

What the hell is up with the subnet mask, and how the hell can I even connect with that IP and subnet combo? Sh!t, you shouldn't even be able to connect to ANYTHING with a subnet mask like that! Someone clue me in.

 

[ScottMac]

A 255.255.255.255 subnet mask is a shortcut for saying "This Node, and only this node."

You may also notice that there is no direct way to subnet.

Of course, it could just be a tired/overworked/fat-fingered employee back at the headend .... ya never know.

If it's working, don't screw with it.


Good Luck

Scott

 

[JackBurton]

If it's working, don't screw with it.

That's the problem, it doesn't work all the time. I think it is a distance issue though (rather than IP). The ISP is working on it...although VERY sloooooowly.

Just for FMI (For My Information), how the hell would that IP scheme work if they assigned everyone different IPs but kept that subnet mask?

 

[spidey07]

A /32 or 255.255.255.255 mask is used for remote connections or point-to-point (PPP or PPPoE) and other connections who don't understand nor need to understand the concept of broadcast. There is no subnet as Scott pointed out - this node and this node only, all others send to your gateway.

In a dial scenario (which is DSL) you assign IP addresses from a poll. Say 64.1.1.0/24. This will give 256 unique addresses to hand out to clients. The dial server is the one responsible for routing, the client does not need nor does not care about IP addresses or subnetting, hence the /32 mask. It only knows "send anything not destined for myself to my gateways which is my own IP address". In a DSL or PPP session that means "spit it out my transmit on this circuit and let the guy receiving it handle it"

Hope that helps! This is common practice for DSL/PPP sessions.

 

[Saltin]

255.255.255.255 = host route.

 

[spidey07]

So Saltin, what happens when the host itself has a /32 mask?

 

[Saltin]

Hehe, now you're pulling me into water Im not familiar with!

Wouldnt it just pass the packets on upstream?

 

[spidey07]

hehhe, man i've got attitude lately.

/32 mask mean send everything to your gateway
In a point-to-point network where there really is no concept of broadcast then it means "spit it out the transmit channel"

So if you had a /24 mask it might not work because the host will go broadcasting on a point-to-point network. depending on how the router is configured it might not respond to these arps.

 

[JackBurton]

spidey07, you're the man! Thanks!

 

[spidey07]

spidey07, you're the man! Thanks!

No, I just play one on ATnet.