topic ACL_Difference in Network Security

ACL_Difference

Ibrahim Jamil — Mon, 11 Mar 2019 23:02:22 GMT

Hi Experts

what is the technical difference betwen:

access-list acl permit tcp host 10.10.10.10 eq 80 any ?

and

access-list acl permit tcp host 10.10.10.10 any eq 80 ?

it confuses a little bit

thanks

jamil

Re: ACL_Difference

Dan-Ciprian Cicioiu — Fri, 04 May 2012 17:49:04 GMT

Hi Ibrahim,

Source IP 10.10.10.10 source port 80 -> any IP destination any port destination

access-list acl permit tcp host 10.10.10.10 eq 80 any ?

Source IP 10.10.10.10 source port any -> any IP destination port destination 80

access-list acl permit tcp host 10.10.10.10 any eq 80 ?

Dan

ACL_Difference

Maykol Rojas — Fri, 04 May 2012 17:52:06 GMT

Jamil,

The first one indicates that the packet from 10.10.10.10 will come with a source port 80. Since TCP connection start with a random source port, the ACL mostlikely is not going to be hit. In case of a Router, where they are more packet wise than connections, it may work, but for an ASA it wont, because a connection needs to be established prior a response on well known port is received.

The second one is more common, it usually allows connection to well known ports for the first SYN packet (in case of TCP connections). That will allow a connection establishment on the ASA firewall, then the return packets will be allowed preventing you the need of configuring ACLs with source ports.

Mike

ACL_Difference

Ibrahim Jamil — Fri, 04 May 2012 18:41:59 GMT

Thanks for ur reply guys