Hi,

Can somebody enlighten me as to why IP address = gateway and why subnet mask = 255.255.255.255???

PPP adapter GlobeSpan Dial-Up PPP Connection:

Connection-specific DNS Suffix . :
IP Address. . . . . . . . . . . . : 210.24.215.121
Subnet Mask . . . . . . . . . . . : 255.255.255.255
Default Gateway . . . . . . . . . : 210.24.215.121

Above is the ipconfig result from a local ISP.

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It looks to me like they are doing some very special configurations here. According to the configuration, any packets originating from the device will be considered remote and will be routed through itself. The node is functioning as a router and because of the IP address and subnet mask, any address other than itself will be remote, so all packets originating will be routed.

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The other reason why this is done is to force the machine to send out arp requests for any other node. There could be some timing issues that are involved that would call for a situation like this.

Reamer

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I called up the ISP and was told by one of the helpdesk guy that this configuration is to help enhancing security for individual node that dials up.

Anyway, I am still utterly baffled and have not come across this in any books so far..

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quote:

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Originally posted by Certaddict
I called up the ISP and was told by one of the helpdesk guy that this configuration is to help enhancing security for individual node that dials up.

Anyway, I am still utterly baffled and have not come across this in any books so far..

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No, no, no (well, at least, experience contradicts this...)

the reason that there's a /32 mask is because it's a point-to-point connection. Ordinarily, the default gateway would be set to the machine at the other end of it (and since it's a p-t-p conn, none of the normal subnetting rules apply and the machine at the other end could have any legal IP address it wanted to.)

Either way, the configuration means the same thing, all that the 'default gateway=my IP' means is that it's going to send all traffic for which there isn't a better route (probably all of it unless you've got a network card in that machine as well) over the PPP link. It's the same as setting a default route through an interface on a Cisco.

Cheers,

Sid

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quote:

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the reason that there's a /32 mask is because it's a point-to-point connection.

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Here's what the good ol' folks at Cisco Systems, Inc. say about the issue:

quote:

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Originally posted at www.cisco.com
No IPCP Options for Default Gateways and Subnet Masks
The NAS and the Windows PC establish a point-to-point connection that runs PPP. The PC acts as a host that does not route IP traffic between multiple interfaces. The PC automatically uses the IP address of the NAS (learned during IPCP negotiation) as the default gateway. The subnet mask is not needed in that point-to-point environment. The PC knows that if the destination address does not match the local address, the packet should be forwarded to the default gateway (NAS) which is always reached via the PPP link.

Inaccurate Information in Winipcfg/Ipconfig
Microsoft opted for displaying the address assigned to the PC as the default gateway address and showing the classful mask for that address instead of leaving those fields blank. Don't worry about this information if IP connectivity through the dial-up adapter is operating correctly.

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And now, to end the suspense... here's --> THE LINK <--

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dmaftei, no personal comments about the setup outside of the Cisco link? Usually you have a comment or two rather than just a Cisco quote...

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quote:

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Originally posted by strikeattack
Usually you have a comment or two rather than just a Cisco quote...

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First of all dial-up is one of my weakest points Then, I've been quite busy lately, and so I didn't have too much time to 'chat' with you, guys... Maybe later...

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