Help! ISP gives /29 Primary SUB1 and /30 Secondary SUB2 but cannot add IP addresses /30 as Secondary

Our ISP will route /30 Secondary subnet to /29 primary subnet (Primary External Interface IP1SUB1/29), so that routing is no issue.
Following instructions for Secondary network in External Interface (Interface Settings/ Add a secondary network) adding IP1SUB2/30 Secondary subnet I get a msg box with the Error:
“IP1SUB2/30 is not a valid secondary network IP address. Add new one or click ‘Cancel’ to exit the dialog.”

just for trial, If I add the secondary network with the same netmask P1SUB2/29, accepts it without error message. But my the secondary network is /30 and not /29.

Please help, is it configuration problem?

Best Answers

  • Accepted Answer

    Thank you Bruce for all your advices, I will try next week.

  • Accepted Answer

    Thank you Bruce, following your advices It works.

Sign In to comment.