Then, for each VLAN that you want the Multilayer switch to route for, you have the option of configuring an IP address within what is known as an SVI, or a Switched Virtual Interface.Īn SVI serves as the 元 termination point for each VLAN – aka, the way in or out of each VLAN. MultilayerSwitch(config-if-range)# switchport access vlan 30 MultilayerSwitch(config)# interface range eth3/0 - 2 MultilayerSwitch(config-if-range)# switchport access vlan 20 MultilayerSwitch(config-if-range)# switchport mode access MultilayerSwitch(config)# interface range eth2/0 - 2 The Switch’s port facing the router is configured as a standard Trunk: This is in reference to the single router terminating the traffic from each VLAN. The Sub-interface feature is sometimes referred to as Router on a Stick or One-armed Router. Keep in mind, however, that the drawback with all VLANs terminating on a single Router interface is an increased risk of congestion on the link. The only difference is with Sub-interfaces, only one Router interface is required to terminate all VLANs. The logical operation of the Sub-interface topology works exactly as the separate physical interface topology in the section before it. Hence, each router Sub-interface must also add a VLAN tag to all traffic leaving said interface. Sub-interfaces to a Router are similar to what Trunk ports are to a Switch – one link carrying traffic for multiple VLANs. That method is to create a Sub-Interface.Ī Sub-Interface allows a single Physical interface to be split up into multiple virtual sub-interfaces, each of which terminate their own VLAN. Instead, there exists a way for multiple VLANs to terminate on a single router interface. If there were five VLANs on the switch, then we would need five switchports and five router ports to enable routing between all five VLANs The previously described method is functional, but scales poorly.
#Router on a stick vlan mac#
The only difference is since there is only one physical switch, there will only be one MAC address table – each entry includes the mapping of switchport to MAC address, as well as the VLAN ID number that port belongs to.Įach switch port in this diagram is configured as an Access port, we can use the range command to configure multiple ports as once:Ĭapability Codes: R - Router, S - Switch, I - IGMP, B - Source Route Bridgeĭevice ID Local Intrfce Holdtme Capability Platform Port ID In fact, the process of a packet moving from Host A to Host D in this topology will work exactly as it does in this video. The Router operates like normal when routing packets between two networks. The Router doesn’t know that it has two connections to the same switch - nor does it need to. The simplest way to enable routing between the two VLANs to simply connect an additional port from each VLAN into a Router. The remainder of this article will explore these three options and their configuration.