When you enable span on a switch as we've got over here the switch no longer learns MAC addresses on
the span destination port.
It also doesn't allow traffic to be received from that port.
So if a one pings write a t it works.
And the MAC addresses are shown in the MAC address table but rather one is not able to ping the capturing
device so filtering for ICMP the pings are being received from right of one to the P.C. but no replies
are being accepted by the switch.
So in other words the ping from the one to the capturing device is received in this port and because
of the port mirroring or span the traffic is being sent out of this port and is received by the capturing
device.
But when the capturing device replies that traffic is not accepted on the destination spend port.
So the pings are failing
so once again notice there were no successes on the ping from Route 1 to the capturing device and just
to confirm that is the IP address of the capturing device.
If we want to allow that device to send traffic we have to configure the monitoring session to receive
that traffic so destination interface is fast Ethernet.
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and we have to add this option ingress to enable ingress traffic forwarding
and to specify that is un tagged traffic in VLAN 1.
So I'll start to the capture again
and let's see if Radha one is able to ping that capturing station notice the pings succeed here's the
ping from Route 1 to the capturing device here's the reply and the pings succeeded.
So just to prove that again I'll do a repeat of just one
play the one shall capture one ping there's the ping sent from Route 1 Here's the reply we've seen duplicates
because we are looking at traffic sent and received on this port so we are receiving duplicates because
we are sending traffic to the monitoring station that's received or transmitted on this port so we get
some duplicates but they point to remember is that if we don't use the ingress command the monitoring
station is not able to participate in the network.
Essentially the MAC address is removed from the MAC address table so the MAC address is not learnt as
you can see over here traffic is not allowed to be received on this interface but with the ingress option
it can be received and the device is allowed to participate in the network.