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Cisco ONS 15327 Troubleshooting Guide, R3.4
April 2003
Chapter 1 General Troubleshooting
CTC Operation Troubleshooting
Procedure: Change VLAN Port Tag and Untagged Settings
Step 1 Display the CTC card view for the Ethernet card involved in the problem VLAN.
Step 2 Click the Provisioning > VLAN tabs (Figure 1-25).
Figure 1-25 Configuring VLAN Membership for Individual Ethernet Ports
Step 3 If the port is set to Tagged, continue to look at other cards and their ports in the VLAN until you find the
port that is set to Untag.
Table 1-24 VLAN Cannot Connection to Network Device from Untag Port
Possible Problem Solution
The Tagged ONS 15327 adds the
IEEE 802.1Q tag and the Untag
ONS 15327 removes the Q-tag
without replacing the bytes. The NIC
of the network device categorizes the
packet as a runt and drops the packet.
See the “Change VLAN Port Tag and Untagged Settings”
procedure on page 1-65.
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 prevents
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 can 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 lose
IEEE 802.1Q compliance.
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.