HEllo, I have a Cisco 2600 router with 2 fast ethernet interfaces. Can I use the 2 interfaces in a bridged mode and filter with acl at layer 3 ? IF so how can I do it ? I would like a transparent bridging between hte two interfaces but at the same time I would like to filter traffic at layer 3. is it possible ?
Not unless this feature has been added in a fairly recent 12.4 Advanced Security release.
This was traditionally not possible with IOS: layer 3 ACLs could only be applied against routed entities (VLANs, routed interfaces), and layer 2 ACLs could only be applied against bridged entities.
The first IOS devices that I can think of that allowed it were the 2950 switches (with lots of restrictions), or the 3550/3750 multilayer switches (with fewer restrictions). If I understand correctly, these days you can do it with Cisco PIX 7.0 or the ASA 5500 series of firewalls (so you could probably also do it with a FWSM blade for the
6500/7200). With the growing convergance between PIX 7.0 and IOS, it could be that it made it into a 12.4 release.