Any Explain this....

On the ADSL port, have a look at the strange Subnet Mask 255.255.255.255

The normal class B subnet mask is 255.255.0.0

Is the subnet mask 255.255.255.255 not used for broadcasts.
 
yea i check that..about the subnet..

still does explain how it was possible 2 have that ip and still surf/downlaod stuff
u do the test change ip/subnet and set like they have and still get error....
 
1: a subnet mask is not an ip address, so it is not used for transmitting anything....
2: a mask of 255.255.255.255 implies a ppp link which has no broadcast or ident so in theory anything can be used.
3: If your subnet allows for more than 255 ip's you will land up using .0 at the end at some stage....
 
"0" is a legit ip character consider localhost is 127.0.0.1 , it's just unusual to see it there.

I'm not sure, but if I'm not mistaken a Subnet mask of 255.255.255.255, will limit all traffic to that single IP address ie loopback only.
 
0 is a legit IP node address, but this depends on the size of the IP network its resides on ... and thats where the mask comes in.

The IP mask defines what part of an IP address represents the network and what part represents the node (i.e your PC's network adapter etc.)

With a mask of 255.255.255.0, the IP address 200.0.0.1 is effectively node 1 on network 200.0.0

With a mask of 255.255.0.0, the IP address 200.0.0.1 is effectively node 0.1 on network 200.0

Usually, but not always, an IP network has 2 special addresses, the first one representing the network address itself, and the last one representing the broadcast address of that network.

In the first example above 200.0.0.0 is the network address & 200.0.0.255 is the broadcast address, and 200.0.0.1 - 200.0.0.254 are the possible node addresses.

In the second example 200.0.0.0 is (still) the network address & 200.0.255.255 is the broadcast address, and 200.0.0.1 - 200.0.255.254 are the possible node addresses.

So in the second example an IP address of 200.0.1.0 is a legit address as its not the network or broadcast address and it falls within the range of possible node addresses.

The smallest possible network allowable is one with 1 node address and uses a mask of 255.255.255.255. As there is no ambiguity to where a packet must be routed to reach the address, the network, broadcast & node addresses are all the same.

So every IP/mask allocated to ADSL interfaces by SAIX, represents an individual 1 node network and therefore a .0 node address is also legit.
 
Although .0 is a legal IP address depending on the subnet mask, it has been my experience that certain badly behaved applications, ie, Windows, don't work properly if they are assigned an address such as this. Same goes for an address that ends with .255.

We use a large subnet here at work (255.255.252.0), however we have excluded the .0 and .255 addresses, since they cause problems.
 
IP Address is not subnet mask. In an IP subnet, the lowest address is the network address, the highest address is the broadcast address. A class C network consist if 256 addresses (xxx.xxx.xxx.0-xxx.xxx.xxx.255), but 0 and 255 are not usable, so the addressing starts at 1 and ends at 254. An IP address with 0 as the last byte is however possible, and a subnet mask of 255.255.255.255 determines that this subnet consists of exactly one IP address. I am not familiar with the protocol constraints in dialup/PPPoE, but I assume that this way of addressing/subnetting is necessary to avoid problems with dialup nodes ending up in the same subnet.

Alex
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X