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Forum Discussion
rbussolotti
Feb 22, 2021Aspirant
Invalid IP - RBR20
Hi, I was assigned a public IP address from my ISP and when configuring it to my router I keep receiving the Invalid IP message. I checked it and I accurately made all the settings as indicated ...
rbussolotti
Feb 22, 2021Aspirant
Yes. Same.
CrimpOn
Feb 22, 2021Guru
I found a fascinating discussion of RFC3021 where the poster recommended using /30 rather than /31 claiming "it will still work".
Does the ISP have a "Level 2" support tier?
(with my (former) Time Warner (now) Spectrum, I had to escalate to Level 2 over several issues.)
- rbussolottiFeb 22, 2021Aspirant
Yes,
the ISP said that if the router doesn't support the RFC 3021 they can provide a /30 class IP at an additional monthly fee. eheheh.
- CrimpOnFeb 22, 2021Guru
rbussolotti wrote:the ISP said that if the router doesn't support the RFC 3021 they can provide a /30 class IP at an additional monthly fee. eheheh.
What a deal (not). Actually, I believe the advice was to cheat. Put in the static IP and the gateway IP and then use a /30 subnet mask instead of a /31 mask. Any broadcasts generated by the router would just 'disappear'
Several internet searches have turned up similar questions for other Netgear routers, but no definite answers.
Does this ISP have a list of supported routers?
- rbussolottiFeb 24, 2021Aspirant
Hi,
I played with the subnet mask a bit.
So:
The invalid IP message was indeed because of the subnet mask .254
I then tried to put .252 but I got the message "Invalid Subnet mask" (???).
The only way fwd was to put .248 and everything went fine. Still unclear to me how come a good device like the Orbi RBR20 has these kind of issues while when putting all the parameters with /31 subnet in my 20 euro wifi router everything worked smoothly at first attempt...
BTW thanks a million for the support.
r
- CrimpOnFeb 24, 2021Guru
rbussolotti wrote:The invalid IP message was indeed because of the subnet mask .254
I then tried to put .252 but I got the message "Invalid Subnet mask" (???).
The only way fwd was to put .248 and everything went fine.
Truly disappointing. Since subnet masks must be "all 1's starting on the left and then all zeros", the only valid subnet masks are 128. 192, 224, 240, 248, 252, and 254. which correspond to /24, /25, /26, /27, /28, /29, /30, /31
II wonder how common it is to use a pair of IP's to define Static IP's? A Class C address, for example, would support about 252 customers (reserving 0, 255 for broadcast, one for the gateway) but only 126 customers using two IP's for each.
The "point to point" method may be more secure. Even if one customer cheats and uses a wider subnet mask, none of the other customers will respond to him because they are limited to the single connection.
p.s. I have sent private messages to two forum moderators asking for comment and not heard back from either.