Cisco ONS 15454 - Change VLAN Port Tagged and Untag Settings

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Cisco ONS 15454 Troubleshooting Guide, R8.5
November 2009
Chapter 1 General Troubleshooting
1.10.17 VLAN Cannot Connect to Network Device from Untag Port
normal runt packets count at the network device attached to the Untag port. This symptom/limitation also
exists when ports within the same card or ports within the same chassis are put on the same VLAN, with
a mix of tagged and untagged.
Possible Cause The Tagged ONS 15454 adds the IEEE 802.1Q tag and the Untag ONS 15454
removes the Q-tag without replacing the bytes. The NIC of the network device categorizes the packet
as a runt and drops the packet.
Possible Cause Dropped packets can also occur when ARP attempts to match the IP address of the
network device attached to the Untag port with the physical MAC address required by the network
access layer.
Recommended Action The solution is to set both ports in the VLAN to Tagged to stop the stripping
of the 4 bytes from the data packet and prevent the NIC card in the network access device from
recognizing the packet as a runt and dropping it. Network devices with IEEE 802.1Q-compliant NIC
cards accept the tagged packets. Network devices with non IEEE 802.1Q compliant NIC cards still
drop these tagged packets. The solution might require upgrading network devices with
non-IEEE 802.1Q compliant NIC cards to IEEE 802.1Q compliant NIC cards. You can also set both
ports in the VLAN to Untag, but you will lose IEEE 802.1Q compliance.
Figure 1-50 VLAN with Ethernet Ports at Tagged and Untag
Change VLAN Port Tagged and Untag Settings
Step 1 Open the CTC card view for the Ethernet card involved in the problem VLAN.
Step 2 Click the Provisioning > Ether VLAN tabs (Figure 1-51).
55243
Workstation #1 ONS Node
with Ethernet card
VLAN port set to Tagged
ONS Node
with Ethernet card
VLAN port set to Untag
SONET/SDH
Ethernet
Workstation #2