What is Q and Q in networking?
802.1Q tunneling (aka Q-in-Q) is a technique often used by Metro Ethernet providers as a layer 2 VPN for customers. By using a different VLAN tag for each customer we can separate the traffic from different customers and also transparently transfer it throughout the service provider network.
What is selective Q-in-Q?
Selective Q-in-Q is the way to achieve Q-in-Q per CVLAN basis, where you have the flexibility to selectively choose and add service VLAN tag based on the customer VLAN.
What is Svlan and Cvlan?
CVLAN tag—Identifies the VLAN to which the frame belongs when it is transmitted in the customer network. SVLAN tag—Identifies the VLAN to which the QinQ frame belongs when it is transmitted in the service provider network. The service provider allocates the SVLAN tag to the customer.
What is 802.1Q trunking?
VLAN Trunking (802.1Q) allows physical network interfaces in a computing environment to be shared, or multi-homed. Network devices on the network then only interact with packets that have the correct tags. This allows multiple different logical networks to run on the same cable and switch infrastructure.
What is outer VLAN and inner VLAN?
Within an Ethernet Frame, these two tags are often known as “Inner tag” and “Outer tag”. “Inner tags” contain VLAN information that belong to the traffic of the NSP’s customers. The “Outer tags” contains information relating to the NSP’s VLAN networks.
What is 802.1Q double tagging?
In a double tagging attack, an attacker connected to an 802.1Q-enabled port prepends two VLAN tags to a frame that it transmits. The second tag is then visible to the second switch that the frame encounters. This second VLAN tag indicates that the frame is destined for a target host on a second switch.
When an 802.1Q tag is added to an Ethernet frame where is it placed?
When an 802.1Q tag is added to an Ethernet frame, where is it placed? It is inserted between the source address and the Ethernet type field.
What is the difference between dot1q and QinQ?
Switchport mode dot1q-tunnel interface level command is used to configure interface carrying Q-in-Q frames. While configuring the Q-in-Q the MTU needs to be carefully addressed, as the frame coming from customer may already contain 1500 bytes and by implementing Q-in-Q adds additional 4 byte in the frame.
What is CV LAN?
CVLAN is the Customer VLAN, SVLAN is the Service VLAN. CVLAN is the VLAN tag the customer is using on their own devices, SVLAN is the VLAN the service provider shoves all the customer traffic in.
What is the difference between QinQ and Dot1q?
Dot1q termination: terminates packets that carry one VLAN tag. QinQ termination: terminates packets that carry two VLAN tags.
What is the MTU size of an Ethernet frame?
Ethernet Version 2 networks have a standard frame size of 1518 bytes (including the 14-byte Ethernet II header and 4-byte Frame Check Sequence (FCS)). It should also be mentioned that other communications media types have different MTU sizes.
Why is the MTU set to 1500 byte?
12-17-2008 03:19 AM the ip MTU is set to 1500 byte this implies an ethernet frame of size 1500+18 can go through. The router will receive it correctly and will extract the ip packet inside the frame and will forward it besides this, ethernet frames cannot be fragmented.
What is the maximum MTU required for Q-in-Q tunneling?
Sometimes a slightly higher MTU is preferable to accommodate Q-in-Q tunneling or other encapsulation. The MTU can be raised on Cisco IOS with the system mtu command under global configuration: The maximum MTU is dependent on the hardware platform, but the IEEE 802.3 standards require a minimum MTU of 1500 bytes.
What is the default Ethernet MTU on Cisco IOS?
The default Ethernet MTU is 1500 bytes, not including the header or trailer. Sometimes a slightly higher MTU is preferable to accommodate Q-in-Q tunneling or other encapsulation. The MTU can be raised on Cisco IOS with the system mtu command under global configuration: