it's a ACL a layer 4 transport layer protocol ?

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I believe an ACL resides in Layer 3. A normal ACL can block a host or block of IP address which are layer 3. An Extended ACL can block a protocol but still uses IP address to do so.

yrwins

thanks.

james43026

From a network point of view, an ACL can go up to layer 4, if we are talking about extended ACL's.

clarson

ip acl is layer 3
an extended acl is either layer 3 or 4

NiceRoute

If it can block logical ports, then it can be referred to as working at layer 4.

OctalDump

No. An ACL is not a protocol. Cisco ACLs can modify the behaviour of traffic from layer 2 up. Typically at CCNA level you deal with ACLs that modifying traffic at layer 3 and 4. Eg, block all traffic from this IP (layer 3), or allow access to only these ports (layer 4) at this IP.

TheFORCE

OctalDump wrote: »

No. An ACL is not a protocol. Cisco ACLs can modify the behaviour of traffic from layer 2 up. Typically at CCNA level you deal with ACLs that modifying traffic at layer 3 and 4. Eg, block all traffic from this IP (layer 3), or allow access to only these ports (layer 4) at this IP.

About to say that, ACL's are not protocols. You can have ACL is many different type of devices.

Cisco Inferno

standard ACL's block L3 traffic based on IP address. Extended ACL's can filter things based on L4 Port info on top of that.
ex. Blocking Port 80 web traffic to a specific subnet. (like a kiosk pc or something)