[c-nsp] cisco ACL filter outbound only

[Nick Hilliard]

Mike wrote on 15/09/2020 02:17:
>      I have some gear that needs a public ip, but does not have the best
> security profile, and I want to put up an ACL that only permits this
> gear to make outbound connections while dropping all inbound. My router
> is an ASR920 running IOS-XE 03.17.03.S. Does anyone have a simple
> copy/paste acl for this type of job?

you're mixing up a packet filtering ACL with a firewall ACL.

A packet filter with this sort of ACL will block all inbound traffic, 
i.e. the performance will be terrific but everything will break because 
return traffic will be blocked (e.g. tcp syns/acks, etc).

A firewall rule will enable dynamic outbound state management, which 
seems to be what you want, but the ASR920 doesn't support it.

You need a firewall for this, not a router.

Nick