A Trunk link is a point-to-point link between two network devices. Trunk link carry more than oneVLAN. With VLAN trunking, we can extend our configured VLAN across the entire network. Remember, sending information from an access link on one VLAN to another VLAN is not possible without the additional device a router or a external layer 2 bridge connected between the VLAN.
A Trunk link can transport multiple VLANs traffic through a single switch port. A trunk link is not assigned to a specific VLAN.
Types of links/ports.
Connecting to end devices (hosts or router)
Part of one VLAN
Do not belong to any VLAN
Its Carry multiple VLANs traffic
It’s a physical Link between two switches
In order to make sure that same VLAN users on different switch communicate with each other there is a method of tagging happens on trunk links. Tag is added before a frame is send and removed once it is received on trunk link. Frame tagging happen only on the trunk links.
VLAN Frame Identification
A Trunk link can transport multiple VLANs traffic; a switch must identify frames with their respective VLANs as they are sent and received over a trunk link.
VLAN identification can be performed usingtwo methods, each usinga different frame identification mechanism:
Inter-switch link (ISL) protocol
IEEE 802.1Q (Dot1Q) protocol
Inter-switch link(ISL) is a Cisco-proprietary method for preserving the source VLAN identification of frame passing over trunk link. ISL work with Ethernet, Token ring, FDDI. ISL adds a 26-bytes header and a byte trailer to the frame you can say its adds 30 bytes of tag. The ISL method of VLAN identification or trunking encapsulation no longer is supported across all Cisco catalyst switch platform.
The IEEE 802.1Qprotocol is also used to carry VLAN traffic, dot1q is a open standard trunking protocol, its work only on Ethernet, dot1q introduce us the concept of Native VLAN on a trunk. The frame belong to native VLAN is not encapsulation and with any tag. Dot1q is only adding 4 bytes tag will be added to original frame just after the source address field.
Hi Guys, Would like to ask for experts advise what are the Disadvantage of implementing Multiple iBGP neighborship in same subnet like flat network? Let's say 4 iBGP routers that are all connected in a switch and routers iBGP neighborship interfaces ...
I will have redundant Internet connections from 2 different carriers. For example one could be China Telecom and the other China Mobile. From the first carrier I will get some address space ( a prefix ) to be used at my site . The question I h...
Hi Guys,Would greatly appreciate your help on this, so I have configured a new sub interface ob Vlan 20and only need DHCP for these clients. problem is that no DHCP is reaching any clients.if i configure a static IP on one of the clients I can ping the ga...
I have a c220 m5 with a VIC 1457. This server is using port-0 and port-1 with 10GB twinax cables split between 2 Nexus 9k's. I am trying to put these to physical connections into a VPC using LACP on each of the switch ports. The only thing I could fi...
dears expertsi am looking for 4 x 10G interfaces and 4 lan ports copper , does ASR-920-12SZ-IM will make my job or i have to choose ASR-920-24TZ-M, also i need the security services so i m confused by the below lines form the datasheet that only...