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KonstantinC
Beginner

A couple of questions about RSPAN

Hi!

Suppose we want to redirect traffic from server on Gi0/1 port on switch SW1 to some destination on SW2 through remote-span vlan 10

http://s42.radikal.ru/i098/1211/47/8a8476ad4888.png

Switch SW1 configuration:

monitor session 1 type rspan-source

source interface Gi0/1

destination remote vlan 10

Suppose that server generates 500MBit\s of traffic.

Question is at what moment the traffic physically will go through trunk to SW2?

There are two trunk ports on SW1 where vlan 10 is allowed.

How SW1 knows where to direct traffic?

1 ACCEPTED SOLUTION

Accepted Solutions
bissaha
Cisco Employee

HI,

Plesae check the RSPAN config guideliens

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swspan.html

Note

As RSPAN VLANs have special properties, you should reserve a few VLANs across your network for use as RSPAN VLANs; do not assign access ports to these VLANs.

--To avoid unwanted traffic in RSPAN VLANs, make sure that the VLAN remote-span feature is supported in all the participating switches.

So to ans your queries see inline

--Question is at what moment the traffic physically will go through trunk to SW2?

Ans:----As soon as we define RSPAN vlan & considering its allowed in the trunk with below configs defined, we should get the traffic onto SW2

SW1

conf t

vlan 10

remote-span

monitor session 1 source interface gi0/1

monitor session 1 destination remote vlan 10

SW2

conf t

monitor session 1 source remote vlan 10

monitor session 1 destination interface X/Y

Q:--How SW1 knows where to direct traffic?

Ans:--If you allow that vlan over to both the SW3 and SW2, it will forward the traffic to both however if you dont have configs for RSPAN (monitor session 1 source remote vlan 10) on the respective switches traffic will be dropped.

Hope this helps.

Regards

Biswa.

View solution in original post

2 REPLIES 2
bissaha
Cisco Employee

HI,

Plesae check the RSPAN config guideliens

http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swspan.html

Note

As RSPAN VLANs have special properties, you should reserve a few VLANs across your network for use as RSPAN VLANs; do not assign access ports to these VLANs.

--To avoid unwanted traffic in RSPAN VLANs, make sure that the VLAN remote-span feature is supported in all the participating switches.

So to ans your queries see inline

--Question is at what moment the traffic physically will go through trunk to SW2?

Ans:----As soon as we define RSPAN vlan & considering its allowed in the trunk with below configs defined, we should get the traffic onto SW2

SW1

conf t

vlan 10

remote-span

monitor session 1 source interface gi0/1

monitor session 1 destination remote vlan 10

SW2

conf t

monitor session 1 source remote vlan 10

monitor session 1 destination interface X/Y

Q:--How SW1 knows where to direct traffic?

Ans:--If you allow that vlan over to both the SW3 and SW2, it will forward the traffic to both however if you dont have configs for RSPAN (monitor session 1 source remote vlan 10) on the respective switches traffic will be dropped.

Hope this helps.

Regards

Biswa.

View solution in original post

Thanks, bissaha

So RSPAN is a dangerous technology

In my case I have 6500 with many trunks, there is also server connected that generates 3Gbit\s of traffic.

If I'll configure

monitor session 1 source interface gi0/1

monitor session 1 destination remote vlan xx

many trunk links where vlan xx is not excluded will be overloaded...