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I can not add /31 subnet mask 255.255.255.254 in WAN ISP > static IP setting in VPN Firewall SRX5308
Hi, I can not add /31 subnet mask 255.255.255.254 in WAN ISP > static IP setting in VPN Firewall SRX5308. When I try to apply it, I get the error message popup as "Invalid IP subnet mask. Please ...
/31 would be used in specific scenarios where you *really* need to conserve address space and only on point-to-point links. To be fair I've never come across anyone, or any ISP, that uses it. It works on point to point because well, there's no need for broadcast address since there are only two devices on the link (one on each side of the cable).. IP ranges would be; .0 - .1, .2 - .3, etc.
Most (if not all) Netgear devices will prevent you from setting /31, but you'll probably be able to use /30 without issues anyways, depending on the ISP setup I don't think it would cause you any issues really. But if you can, I'd definitely ask for a /30 instead.
Hi Ridwan,
The /31 subnet mask is really invalid. I am not sure why it is accepted on the SnapGear SG560. Are you able to go online just with the /31 subnet mask configured on the SnapGear SG560?
Kindly verify the subnet mask given to you to your ISP.
Regards,
DaneA
NETGEAR Community Team
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