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Router won't take 16bit subnet on IP address assignment

This is a new config.  Can't get past the address assignement.

Why do the 8 bit and 24 bit subnet masks work but the 16 bit mask errors.

The IOS ver is a little old so I am going to update and see if that works but if you have other ideas please share them

IOS (tm) 2500 Software (C2500-I-L), Version 11.2(18)

router#config t
Enter configuration commands, one per line.  End with CNTL/Z.
router(config)#int e0
router(config-if)#ip address
Bad mask /16 for address
router(config-if)#ip address
router(config-if)#ip address
  • 2
1 Solution
Use the "ip classless" command, it is enabled by default in IOS versions 12.0 and higher but disabled by default in previous IOS's (like yours).

router(config)#ip classless
Also, enable the following if not already:

router(config)#ip subnet-zero
Don JohnstonInstructorCommented:
You're trying to create an all zero's subnet. That's not allowed unless, like JFrederick mentions, you issue the "ip subnet-zero" command.

everythingbutthemooAuthor Commented:
Thanks, that worked.

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