Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

join switch ports together

cisco 2651XM router

IOS: c2600-adventerprisek9-mz.124-15.T9.bin

NM-16-ESW switch fitted

regarding the switch ports (F1/0 to F1/15):

is there a command that will join two or more switch ports together and make them act as plain hub ports?

12 REPLIES
Hall of Fame Super Gold

Re: join switch ports together

"join two or more switch ports together"
You mean etherchannel?  Yes, it's supported.


"make them act as plain hub ports"
Hub ports?  Can you please elaborate?  Otherwise you can put/assign two or more ports into a VLAN.

New Member

Re: join switch ports together

the ports in question are already on the same vlan, but I want them to behave as plain hub ports and not switch ports.

New Member

Re: join switch ports together

I'm not sure I catch your drift here. Ports in the same VLAN are in the same broadcast domain a la a hub albeit not in the same collision domain.

New Member

Re: join switch ports together

yes that's it, I want two or more ports in the same collision domain, just like a hub.

Cisco Employee

Re: join switch ports together

Hi,

On a switch, each port will be in a different collision domain. This is one maj

Do you have any specific reason to have 2 ports in same collision domain?.

Regards,

Nagendra

New Member

Re: join switch ports together

yes I do have a reason.

is there a command that will join two or more switch ports so they are in same collision domain? - like a hub?

Hall of Fame Super Gold

Re: join switch ports together

I have no idea about the others but I still don't know why you want a Layer 2 switch to behave exactly like a Layer 1 hub.  How about connecting both ports to a hub?  Are you trying to set up packet sniffing?

New Member

Re: join switch ports together

yes I am currently using the monitor command on the router to sniff packets on a port, but I'm only allowed one monitor session at a time on my platform so I can only sniff one switch port at a time. I've got a PC running wireshark connected to the monitor destination port for packet sniffing. I know I could use a hub to sniff multiple ports but it would be more convenient if I could do away with the hub and sniff multiple ports from the NM-16-ESW switch I'm using.

New Member

Re: join switch ports together

monitor session 1 source vlan x

That should do you on multiple ports in the same VLAN.

Or monitor session 1 source int fa 0/1, 0/2, 0/3 if you want to tie down particular ports.

New Member

Re: join switch ports together

thanks for your response, but I can't get those commands to work.

router(config)#monitor session 1 source vlan 1
SPAN Source Vlan is not supported in this platform

router(config)#monitor session 1 source int fa 0/1, 0/2, 0/3

doesn't work either. It doesn't recognise the commas, doesn't recognise spaces, doesn't seem to allow more than one port to be specified - unless I'm doing it wrong.

if I query what's available this is what I get:

router(config)#monitor session 1 source int ?
  FastEthernet  FastEthernet IEEE 802.3
  Port-channel  Ethernet Channel of interfaces:

there doesn't seem to be any way to choose multiple ports.

New Member

Re: join switch ports together

hang on I think I might have got it. I had no idea there were more configs available after the FastEthernet number. This command appears to have done the trick:

router(config)#monitor session 1 source int fa 1/14 - 15

I can now sniff traffic on the these two ports.

I originally tried sniffing four ports (12 - 15, to include my cisco ip phone) but this seemed to knock the phone out. The above command seems to work for a range of ports but I still haven't worked out how to select specific ports.

Hall of Fame Super Blue

Re: join switch ports together

tonyspcrepairs wrote:

yes I do have a reason.

is there a command that will join two or more switch ports so they are in same collision domain? - like a hub?

It's not 20 questions. The reason you were asked why you wanted to do it was that there might be a different way to achieve what you want.

Can a switch act as a hub - sure, a switch can only hold so many mac-addresses in it's cam table and if the cam table is full then it has to flood all packets to all ports. So just get typing with the mac-addresses

Jon

1289
Views
0
Helpful
12
Replies