Loop back like port on an IOS Switch.

[markkwong]

How can i setup a switch ethernet port to always send back what it received on the same port?

Computer---->switch     switch always sends back the ata the computer sends it.

Is there a route option for that?

Thanks,

Mark

[Amit Aneja]

Mark,

Why would you want to do that? Switch will never send back that data computer sent it.

Regards,

Amit

[Peter Paluch]

Hello Mark,

There is no such functionality available. Note that it would in essence cause a loop in network which is something all manageable switches are trying to avoid.

Why would you need such a thing?

Best regards,

Peter

[Leo Laohoo]

How can i setup a switch ethernet port to always send back what it received on the same port? 
Computer---->switch     switch always sends back the ata the computer sends it.

You're not trying to "sniff" the packet using a packet sniffer like WireShark are you?

[markkwong]

This specific system requires a pack to be sent out to the switch and be sent back from the same port. Just like a loop back, so there is absolutly no loop back functionality for IOS? I would think so.

[markkwong]

Also, yes, I'm using wireshark to only Test to see if i can get the same packet back from the same port after sending a PING.

Just for test. 

[boss.silva]

Hello,

If your application requires it for whatever reason i can't think about , then get another NIC and send the traffic to this nic that will only receive traffic from the other port using SPAN for instance, or switchport capture.

Regards,

Bruno Silva.

[HummusChipsSalat]

well, i will try to answer this bizzar question with a bizzar answer that would not get me into the hall-of-fame of cisco's forum life but would nonetheless, force the traffic to return to the same port ,

you could potentially do this : [ but you dont do that , cause the very aim of doing that suggests perhaps someone misinterpreted someone else  ] :

1. connect a single NIC to the switch .

2. the packet you send has a destination

3. if your switch is a Layer3 switch with PBR capabilities, you may create a PBR (policy based) which matches that packet / traffic   and return it by set ip nexthop with the ip of the source that sent it

  that way you would receive it and re-send it again . unless of course you would filter it on that NIC . or untill end of ttl days .

Thats not a Loopback but it would send back the traffic you would send .

[Joseph W. Doherty]

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Posting

Not sure whether Cisco switches support it, but the UDP or TCP echo port will send back the original packet.  If supported, you would need to insure the service is activated.

See http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_tech_note09186a008019d97a.shtml for more info.