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New Member

Converting a Switch port to HUB port

Hi,

I would like to know how i can make a port from a switch to work like a hub port.

Regards

LR

13 REPLIES
Purple

Re: Converting a Switch port to HUB port

What do mean and what are you trying to accomplish. Anyway the answer is no you cannot make it like a hub. If you are just trying to make it like 10 meg half duplex then you just hardcode the speed for that.

New Member

Re: Converting a Switch port to HUB port

Hi,

What i'm trying to acomplish is to make 3 ports, from a switch to work as a hub, that is repeat everything between them.

Is this possible?

Regards

LR

Purple

Re: Converting a Switch port to HUB port

Not that I know of.

Silver

Re: Converting a Switch port to HUB port

If you do not configure any specify features at these 3 ports, it should normally act as a hub or create a VLAN for these 3 ports. The differene is all three ports have dedicated BW. Could you elaborate more on what application will running on these ports ?

New Member

Re: Converting a Switch port to HUB port

Hi,

The application is an IDS.

Does this Help?

Regards

LR

New Member

Re: Converting a Switch port to HUB port

you can copy all the traffic to a single switch port, where you connect the IDS

New Member

Re: Converting a Switch port to HUB port

Yes this does help as meantioned.

Use the span fucntion but if you really doesn't want too I have a few tricks up my sleeve.

1. Try to force the mac-adress table to have a size of 0. That way it won't learn any mac-adresses. Packet with unknown mac-adresses are flooded.

2. Same trick otherways around. Use a hacker tool to send a lot of packets with random mac-addresses. That way you will fill the mac-address table to the max. Other packets will then be floodded.

3. Give both systems (out side the IDS) a multicast-mac adress. When multicats is not implemented in you network this will again flood traffic to all ports in the same vlan. (not only that switch)

All these options are not really good networking practise but hey if you want other options than span

If you can or doesn't want to use span you can.

1. Put a hub in front

2. Use a tap

3. put the IDS in-line

* Please rate my post

New Member

Re: Converting a Switch port to HUB port

Hi,

Ok, I will try it.

Thanks

LR

Re: Converting a Switch port to HUB port

Hi,

I think the feature you are looking for is SPAN.

(Switch Port Analyzer).

here is a sample config:

C2950#configure terminal

C2950(config)#

C2950(config)#monitor session 1 source interface fastethernet 0/2

!--- This configures interface Fast Ethernet 0/2 as source port.

C2950(config)#monitor session 1 destination interface fastethernet 0/3

!--- This configures interface Fast Ethernet 0/3 as destination port.

C2950(config)#

C2950#show monitor session 1

Session 1

---------

Source Ports:

RX Only: None

TX Only: None

Both: Fa0/2

Destination Ports: Fa0/3

C2950#

You can get all the information you need here

http://www.cisco.com/warp/public/473/41.html

Cheers

Stephen

PS: Please rate my posts

========================== http://www.rconfig.com A free, open source network device configuration management tool, customizable to your needs! - Always vote on an answer if you found it helpful
New Member

Re: Converting a Switch port to HUB port

Hi,

Ok! I already known about span. I tought there was another option that could put some switch ports in hub alike ports.

Thanks you all

Regards

LR

Re: Converting a Switch port to HUB port

OK!!! If you already know about SPAN then i would asume that you are a CCNP at least... If that is the case then i also assume that you have THE basic knowlodge of the architectural dirffernces between switches and 'hubs'.

Given all the above then you know that switch ports do not, and cannot act like switch ports under any circumstances... except when SPAN is used.

Switch ports do not forward unicast traffic to all ports - only the port to which the destination MAC address is assigned. Hubs forward unicast traffic to all ports as 'HUBs' do not have a MAC addres Table.

Do not ask silly questions, and then give a silly response to someone that helps.

Regards

Stephen

PS. Just a bit annoyed at the arrogance that can be in the Cisco forums sometimes.

========================== http://www.rconfig.com A free, open source network device configuration management tool, customizable to your needs! - Always vote on an answer if you found it helpful
New Member

Re: Converting a Switch port to HUB port

Switch DOES forward unicasts to all it's ports, if the destination MAC-address unknown. It doesn't make indeed much difference in this case, just a nice thing to know.

And never underestimate the power of other peoples reflection. ;) There is a nice feature on Catalyst 6500, for example. If you're configuring vlan access-list you are able to do the following:

action {{drop [log]} | {forward [capture]} | {redirect {interface interface-number}} | {port-channel channel-id} {interface interface-number} | {port-channel channel-id} ...}

where:

forward

Forwards (switched by hardware) the packets to its destination.

capture

(Optional) Sets the capture bit for the forwarded packets so that ports with the capture function enabled also receive the packets.

I dunno, how to enable capture, but the next option looks perfectly suitable for our case too

redirect interface

Redirects packets to the specified interfaces; possible valid values are ethernet, fastethernet, gigabitethernet, tengigabitethernet, pos, atm, and ge-wan.

It's not proved here, but I don't see why shouldn't it work. Yes, it doesn't make a hub from a switch and overweighted, but is able to do the job, if someone desire it so bad. :)

New Member

Re: Converting a Switch port to HUB port

I have always used SPAN when putting IDS on the line. Switches will not work like a hub but you can redirect all traffic from any number of ports to a single port, thus making it behave like a hub. SPAN is the only way you can do this...the only way that makes sense anyway. Otherwise, there are actual hardware differences that make a switch not be a hub.

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