Subnet mask for management networks in ASDM (need to use a /22)

[spfister336]

I am trying to add a management network to ASDM to manage an ASA. The subnet mask of this network is 255.255.252.0. This subnet is not listed as one of the choices, and if I type it I get "The network address is not valid". Can I not use this subnet mask?

[Marius Gunnerud]

If I understand correctly you are trying to add the /22 subnet to be able to administer the ASA via ASDM.

If that is the case you can do this by CLI.

http 172.16.0.0 255.255.252.0 inside  <replace inside with the ingress interface that MGMT traffic will enter on>

[spfister336]

Tried doing it on the command line, but still get an error:

WARNING: IP address <10.99.199.0> and netmask <255.255.252.0> inconsistent

I know I'm missing something obvious here, but I'm not seeing it...

[Rob Ingram · Accepted solution]

Hi,
That would not work, you'd need to specify 10.99.196.0 netmask 255.255.252.0, which would incorporate the 10.99.199.0 network.

HTH

[spfister336]

Thank you! I knew it was going to be something simple. I probably should have tried it out in a CIDR calculator.