I know this is an older question in response to the question below,
especially considering it is about OEQs but I thought I would add something.

http://www.onlinestudylist.com/archives/ccie_security/2011-August/027594.html

I think Yusef's answer is correct in that only Inline VLAN Pair would work
but not for reason mentioned. VLAN Groups as far as I understand them
actually require two interfaces on the IPS with a different switch
connected to each IPS interface.

Correct me if I am wrong, but VLAN groups pair VLAN a, b and c on interface
one with VLAN a, b and c respectively on interface two. Because the VLANs
paired do infact have the same VLAN ID, they must exist on different
switches which therefore requires two interfaces on the IPS. If the VLANs
being bridged in VLAN group mode were on the same switch the IPS wouldn't
be able to bridge them as the communications would stay on the switch
because the IPS is bridging a VLAN ID with itself.

The fact that the IPS bridges VLANs in Inline VLAN pair mode that have
different VLAN IDs, i.e pair VLAN a to b and VLAN c to d, the traffic must
travel via the IPS in order to pass between VLANs even though they are on
the same switch. This allows only Inline VLAN pair mode to work with a
single interface.

As I said, this is not relevent these days with OEQs being EOL but I
thought it may add to the general discussion.

Thanks
Ben




You are correct.

But when using vlan group, you configure sub-interfaces but the task just
talks about physical interface. May be this can justify the given answer.


With regards
Kings

On Tue, Aug 2, 2011 at 6:25 AM, Bruno <bruno.gimenez at gmail.com
<http://onlinestudylist.com/mailman/listinfo/ccie_security>> wrote:

>* *Question:**>* If the Cisco IPS sensor hardware had only one physical 
>sensing interface,*>* which mode could be used to perform monitoring and what 
>protocol is used on*>* the Catalyst switch to support this scenario?*>**>* 
>*Correct Answer:**>* Inline VLAN pair mode using 802.1q trunk port on the 
>switch*>**>**>* Why not vlan group interfaces which can be achieved by one 
>interface and*>* trunk on switches as well?*>**>* --*>* Bruno Fagioli*>* Cisco 
>Security Professional*>**>* _______________________________________________*>* 
>For more information regarding industry leading CCIE Lab training, please*>* 
>visit www.ipexpert.com*>**>* Are you a CCNP or CCIE and looking for a job? 
>Check out*>* www.PlatinumPlacement.com*>**-------------- next part 
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