ccna vs network+

ccna vs network+.ISL is Cisco-specific and is being phased out in Cisco products, replaced by the IEEE Intermediate Standard 802.1Q, introduced in 1998.One of the advantages of this IEEE standard is that it supports trunking between devices from different vendors, whereas ISL is only supported by some Cisco devices. Therefore, it should be possible to implement a multi-vendor trunking solution without having to worry about whether a particular type of trunking connection is supported. 2960 switches and Cisco high-end switches (such as the 6500 series switches) both support 802.1Q, in fact, the 2960 series switches only support 802.1Q, not ISL. Only Fast Ethernet and Gigabit Ethernet ports on the switch support 802.1QoFigure 12.5 Example of broadcast traffic802.1Q trunk connections support two types of frames: tagged and untagged. Untagged frames do not contain VLAN identification information; they are effectively unmodified Ethernet frames. The VLAN to which an untagged frame belongs depends on the configuration of the switch port: if the port belongs to VLAN 1, the untagged frame also belongs to VLAN lo this VLAN is often referred to as the native VLAN. tagged frames contain VLAN information, and only devices that support 802.1Q can process them.802.1Q is unique in that both tagged and untagged frames can be transmitted over a trunk connection, as shown in Figure 12.6. In this example, frames transmitted by the white VLANs (PC.A, PC.B, PC-E, and PC.F) over a trunk connection between Switch A and Switch B are tagged. The devices on this trunk connection must have 802.1Q enabled so that they can see the tags in the frames and thus determine which VLAN the frames come from. o In this network, there is a third device on this trunk connection: the PC-Go Here it is assumed that the two switches and the PC-G are connected together through a hub.The PC-G is using a regular Ethernet NIC,which obviously cannot understand the tagging and therefore discards these frames. However, here comes the problem T:PC.G belongs to theBlack VLAN, which also contains members PC-C and PC.D. Therefore, to forward frames between these three members, the trunk connection must also support untagged frames so that PC.G can process them. To do this, the connection between the two switches needs to be configured as an 802.1Q trunk connection with the native VLAN specified as a black VLAN, so that frames from the black VLAN will not be tagged when they flow through the trunk connection, allowing PC-G to process them.One restriction on the 802.1Q trunk connection configuration is that the native VLANs must be the same at both ends. In other words, if the native VLAN is a black VLAN on the switch at one end, the native VLAN must also be set to a black VLAN on the switch at the other end; similarly, frames tagged with a white VLAN on one switch must also be tagged with a white VLAN on the other switch using 802.1Q information.PC-A PC-B PC-EFigure 12.6 802.1Q Trunked Connections and Native VLANs Using the Tagging Method When 802.1Q is used, the original Ethernet frame is modified. In the header of the original Ethernet frame, a 4-byte field one tag field is inserted and the first 2 bytes of the frame's FCS (checksum) tag field are recalculated as the protocol identifier, e.g., Ethernet frame