06-30-2008 04:28 AM - edited 03-05-2019 11:54 PM
Hi
I've many switch Cisco which have a problem with mac-address. For example, on one switch cisco 2950, when I connect a pc on interface fa0/8, I don't have address mac when I launch the command "show mac-address-table interface fastEthernet 0/8".
The configuration of interface fa0/8 is :
switchport access vlan 10
switchport mode access
Why ?
Thanks
06-30-2008 05:09 AM
Hello Jean,
a transparent bridge like an ethernet LAN switch can learn a MAC address only when the PC NIC speaks on the wire.
If you are using DHCP you can trigger the PC NIC to speak by performing ipconfig / renew in the shell.
After this the switch port should learn the PC's NIC MAC address.
Prerequisite is that the port is up/up so the two ports agree on speed and duplex or after a successful negotation or because they are statically configured in the same way.
Hope to help
Giuseppe
06-30-2008 05:13 AM
Hello Jean,
another thought is the following: when the switch port comes up it has to go through the STP states of blocked, listening, learning and forwarding
so when you connect a PC to fas0/8 be prepared to wait at least 50 seconds before the port can learn the MAC address and be full operational.
On an access port you can reduce this time by issuing the spanning-tree portfast command
Hope to help
Giuseppe
06-30-2008 05:11 AM
Is there anything plugged into the ports? Are there nodes plugged in but may not be switched on? Maybe the MAC's have timed out - try pinging from a node on one of switch ports to the DG and then check MAC table again.
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