Port span on 3750switch

Answered Question
Apr 2nd, 2010
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Hi,


Looking for some advice on creating a SPAN port. The situation is something like this: there is an existing replication server (say ABC) and there is another server (say XYZ) which is sort of acting as log collector server. SPAN needs to be created for XYZ server to collect/listen to data from ABC server.

Both these servers are on different vlans.All these reside on same switch.

1. Can i use another spare port on the same switch to actually become SPAN port for this purpose. It appears that XYZ server has multiple NIC's and would be connected to this proposed SPAN port, so that management & data collection is done seperately.


Is this feasible? If so, do i need to put this spare port on some specific vlan or leave it on default vlan(which to me means there wont be any ip configured on the XYZ server NIC connecting to this interface) and just configure monitor sessions on this port.


Appreciate all your help in advance.


Thanks!

Correct Answer by Jon Marshall about 6 years 11 months ago

suthomas1 wrote:


Hi,


Looking for some advice on creating a SPAN port. The situation is something like this: there is an existing replication server (say ABC) and there is another server (say XYZ) which is sort of acting as log collector server. SPAN needs to be created for XYZ server to collect/listen to data from ABC server.

Both these servers are on different vlans.All these reside on same switch.

1. Can i use another spare port on the same switch to actually become SPAN port for this purpose. It appears that XYZ server has multiple NIC's and would be connected to this proposed SPAN port, so that management & data collection is done seperately.


Is this feasible? If so, do i need to put this spare port on some specific vlan or leave it on default vlan(which to me means there wont be any ip configured on the XYZ server NIC connecting to this interface) and just configure monitor sessions on this port.


Appreciate all your help in advance.


Thanks!


Yes it's feasible. Use the spare NIC to connect to the SPAN port. You don't need to configure an IP address on it if you don't want to. Make sure that there is no forwarding between the NICs on the server and for safety make sure the port that is the SPAN port is in a different vlan than the other NIC on the server. It can be in any vlan so if you want to you can simply create a vlan for the SPAN port.


Jon


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Correct Answer
Jon Marshall Fri, 04/02/2010 - 03:58
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suthomas1 wrote:


Hi,


Looking for some advice on creating a SPAN port. The situation is something like this: there is an existing replication server (say ABC) and there is another server (say XYZ) which is sort of acting as log collector server. SPAN needs to be created for XYZ server to collect/listen to data from ABC server.

Both these servers are on different vlans.All these reside on same switch.

1. Can i use another spare port on the same switch to actually become SPAN port for this purpose. It appears that XYZ server has multiple NIC's and would be connected to this proposed SPAN port, so that management & data collection is done seperately.


Is this feasible? If so, do i need to put this spare port on some specific vlan or leave it on default vlan(which to me means there wont be any ip configured on the XYZ server NIC connecting to this interface) and just configure monitor sessions on this port.


Appreciate all your help in advance.


Thanks!


Yes it's feasible. Use the spare NIC to connect to the SPAN port. You don't need to configure an IP address on it if you don't want to. Make sure that there is no forwarding between the NICs on the server and for safety make sure the port that is the SPAN port is in a different vlan than the other NIC on the server. It can be in any vlan so if you want to you can simply create a vlan for the SPAN port.


Jon


Cisco are currently donating money to the Haiti earthquake appeal for every rating so please consider rating all helpful posts.

suthomas1 Fri, 04/02/2010 - 04:03
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Thanks for that very useful reply.

A small query though, when other nic of server is connected to this spare port (without any ip) , will it be able to communicate for this purpose.( i believe the port needs to be up for this).

Will it be so when the nic is connected to this port.


Thank You!

Jon Marshall Fri, 04/02/2010 - 04:05
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  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

suthomas1 wrote:


Thanks for that very useful reply.

A small query though, when other nic of server is connected to this spare port (without any ip) , will it be able to communicate for this purpose.( i believe the port needs to be up for this).

Will it be so when the nic is connected to this port.


Thank You!


Port needs to be up but it only needs to receive the traffic ie. it won't send anything on this NIC. And the switch will simply send all traffic seen on your source port(s) to the destination port.


Jon

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