Cisco ME 3400 User Manual

13-5
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 13 Configuring IEEE 802.1Q Tunneling and Layer 2 Protocol Tunneling
Configuring 802.1Q Tunneling
• Ensure that the native VLAN ID on the edge-switch trunk port is not within the customer VLAN
range. For example, if the trunk port carries traffic of VLANs 100 to 200, assign the native VLAN
a number outside that range.
Figure 13-3 Potential Problem with 802.1Q Tunneling and Native VLANs
System MTU
The default system MTU for traffic on the switch is 1500 bytes. You can configure Fast Ethernet ports
to support frames larger than 1500 bytes by using the system mtu global configuration command. You
can configure Gigabit Ethernet ports to support frames larger than 1500 bytes by using the system mtu
jumbo global configuration command. Because the 802.1Q tunneling feature increases the frame size
by 4 bytes when the metro tag is added, you must configure all switches in the service-provider network
to be able to process maximum frames by increasing the switch system MTU size to at least 1504 bytes.
The maximum allowable system MTU for Gigabit Ethernet interfaces is 9000 bytes; the maximum
system MTU for Fast Ethernet interfaces is 1998 bytes.
802.1Q Tunneling and Other Features
Although 802.1Q tunneling works well for Layer 2 packet switching, there are incompatibilities between
some Layer 2 features and Layer 3 switching.
Note Layer 3 switching is supported only when the metro IP access image is running on the switch.
802.1Q
trunk port
VLANs 30-40
Native VLAN 40
Tunnel port
Access VLAN 30
Tunnel port
Service
provider
Tag not added
for VLAN 40
Ta g
removed
VLANs 5-50
Switch D
Customer X
VLANs 30-40
Native VLAN 40
Switch B Switch C
QQ
Switch E
Customer Y
Switch A
Customer X
Native
VLAN 40
101820
Trunk
Asymmetric link
Correct path for traffic
Incorrect path for traffic due to
misconfiguration of native VLAN
by sending port on Switch B
Q = 802.1Q trunk ports
Tunnel port
Access VLAN 40
Packet tagged
for VLAN 30
VLAN 40

Cisco ME 3400 Specifications

General

Category	Switch
Rack Mountable	Yes
Jumbo Frame Support	Yes
Authentication Method	RADIUS, TACACS+
RAM	128 MB
Flash Memory	32 MB
Power Device	Internal power supply
Model	ME 3400
Layer	Layer 2
MAC Address Table Size	8000 entries
Remote Management Protocol	SNMP, Telnet, SSH, HTTP, HTTPS
Features	VLAN support, IGMP snooping, Quality of Service (QoS)
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.1D, IEEE 802.1Q, IEEE 802.3ab, IEEE 802.3x
Memory	128 MB
Power Supply	AC 120/230 V (50/60 Hz)
Dimensions (H x W x D)	4.4 cm x 44.5 cm x 24.2 cm
Routing Protocol	Static routing