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New Member

Lost connectivity after setting up SPAN

I sit on fe 0/18 and I was trying to span fe 0/15 becuase im trying to learn sniffers etc..however after I created the span my port shut down-only after did i directly console into the 2950 did the port come back up-this is what i created-

2950(config)#monitor session 1 source interface fastEthernet 0/15 both

2950(config)#monitor session 1 destination interface fastEthernet 0/18

after i hit enter i lost my LAN connection.

I had to console-disable the session

11w2d: %SYS-5-CONFIG_I: Configured from console by console

11w2d: %LINK-3-UPDOWN: Interface FastEthernet0/18, changed state to up

11w2d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/18, changed

state to up

Im not sure why this came up like this after

i disabled the session-the only thing on the other end of the lan cable is a docking station becuase my laptop was directly consoled into the switch

7 REPLIES
New Member

Re: Lost connectivity after setting up SPAN

When creating a SPAN port, the destination port will be in the up/down state. You will only be able to look down onto the switch not pass any traffic.

New Member

Re: Lost connectivity after setting up SPAN

so if i had wireshark on my pc-i would still see

traffice from the source even though my port is in an updown?

and what would the workaround to getting back "online" per se...do i have to console in everytime?

New Member

Re: Lost connectivity after setting up SPAN

Yes you will be able see/capture to the traffic even know the datalink layer is in the down state.

You could vty in from a workstation that is on a different port on the switch.

If that is not an option you will have will have to console in.

After setting up a SPAN, the destination port of the monitoring session will automatically go into the up/down state, no L2 traffic is allowed.

New Member

Re: Lost connectivity after setting up SPAN

thx for the info...If im doing a remote span..and I only have one one trunk/physical connection

going from switch A to B to C-all on vlan1

switchC---trunk---switchB---trunk---switchA----router

The source is on switch C and the destination is on A

Will all device/hosts lose connectivity to the router which is connected to switch A because

the trunks become reflectors?

Hi

Hi

As I have working the sniffers is, left the destination port like by default, not configuration at all, because it will be used for sniffing only. Now Usually the server have 2 NICs, one for management and the other one for sniffer.

Hope it is useful.

:-)

New Member

I now have this issue, I

I now have this issue, I thought (using your example)

2950(config)#monitor session 1 source interface fastEthernet 0/15 both <-- target port/PC

2950(config)#monitor session 1 destination interface fastEthernet 0/18 <-- sniffing port/wireshark

May I know what was your solution or final thoughts?

New Member

This is standard behaviour

This is standard behaviour for SPAN destination ports. You can't remain connected to the LAN whilst being a SPAN destination port unless you have more than one NIC on your client.

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