How to configure Inter‐VLAN routing (Router‐on‐a‐stick) Router‐on‐a‐stick or Inter‐VLAN routing is a term frequently used to describe a setup up that consists of a router and switch connected using one Ethernet link configured as an 802.1q trunk link. In this setup, the switch is configured with multiple VLANs and the router performs all routing between the different networks/VLANs. While some believe the term 'router‐on‐a‐stick' sounds a bit silly, it's a very popular term and commonly used in networks where no layer‐3 switch exists. LAB Diagram: Networking devices and notes for this LAB 1‐ Cisco Switch WS‐C2960+24TC‐L: 2 Units 2‐ Mikrotik RouterBoard (hAP lite): 1 Unit 3‐ PCs 4‐ UTP Cat6 cables 5‐ Console cable Task to be completed 1‐
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Configure VLAN Configure VTP Assign ports to VLANs for switches Configure Etherchannel on switches Configure Bonding interface on Mikrotik RB Enable RSTP for both switches and assign root bridge Configure Trunk ports Create sub‐interfaces for VLANs on Mikrotik RB Configure DHCP on Mikrotik RB for all VLANs Challenging Problem (How to offer IP addresses to all VLANs by using DHCP server which is not running on Mikrotik RB) Task 1 ‐ Configure VLAN First step is to create the required fives VLANs on our switch 1 named S1 as below VLAN info: ‐
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VLAN2 (Building‐A): 192.168.2.0/24 VLAN3 (Building‐B): 192.168.3.0/24 VLAN98 (Native): 192.168.250.0/24 VLAN99 (Management): 192.168.1.0/24 VLAN255 (Server): 192.168.254.0/24 On Switch 1 (S1): S1# configure terminal S1(config)# vlan 2 S1(config‐vlan)# name Building‐A S1(config)# vlan 3 S1(config‐vlan)# name Building‐B S1(config)# vlan 98 S1(config‐vlan)# name Native S1(config)# vlan 99 S1(config‐vlan)# name Management S1(config)# vlan 255 S1(config‐vlan)# name Server S1(config‐vlan)# exit S1(config)# int vlan 99 S1(config‐if)# ip add 192.168.1.1 255.255.255.0 S1(config‐if)# no shut S1(config‐if)# end Task 2 ‐ Configure VTP On Switch 1 (S1): Configure S1 as VTP server S1# configure terminal S1(config)# vtp domain sopheary.com S1(config)# vtp mode server S1(config)# vtp version 3 S1(config)# vtp password MyvtpSopheary S1(config)# exit S1# vtp primary S1# show vtp status On Switch 2 (S2): Configure S2 as VTP client S2# configure terminal S2(config)# vtp domain sopheary.com S2(config)# vtp mode client S2(config)# vtp version 3 S2(config)# vtp password MyvtpSopheary S2(config)# exit S2# show vtp status S2# configure terminal S1(config)# int vlan 99 S1(config‐if)# ip add 192.168.1.2 255.255.255.0 S1(config‐if)# no shut S2(config)# exit Task 3 – Assign ports to VLANs for switches On Switch 1 (S1): Assign the following ports to each VLAN: ‐
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Port F0/13, F0/14: VLAN2 (Building‐A) Port F0/15, F0/16: VLAN3 (Building‐B) Port F0/17, F0/18: VLAN255 (Server) Port F0/21, F0/22: VLAN99 (Management) S1# configure terminal S1(config)# int range f0/13‐14 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# switchport access vlan 2 S1(config‐if‐range)# spanning‐tree portfast S1(config‐if‐range)# no shutdown S1(config‐if‐range)# int range f0/15‐16 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# switchport access vlan 3 S1(config‐if‐range)# spanning‐tree portfast S1(config‐if‐range)# no shutdown S1(config‐if‐range)# int range f0/17‐18 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# switchport access vlan 255 S1(config‐if‐range)# spanning‐tree portfast S1(config‐if‐range)# no shutdown S1(config‐if‐range)# int range f0/21‐22 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# switchport access vlan 99 S1(config‐if‐range)# spanning‐tree portfast S1(config‐if‐range)# no shutdown S1(config‐if‐range)# end S1# show vlan brief On Switch 2 (S2): Assign the following ports to each VLAN: ‐
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Port F0/13, F0/14: VLAN2 (Building‐A) Port F0/15, F0/16: VLAN3 (Building‐B) Port F0/17, F0/18: VLAN255 (Server) Port F0/21, F0/22: VLAN99 (Management) S2# configure terminal S2(config)# int range f0/13‐14 S2(config‐if‐range)# switchport mode access S2(config‐if‐range)# switchport access vlan 2 S1(config‐if‐range)# spanning‐tree portfast S2(config‐if‐range)# no shutdown S2(config‐if‐range)# int range f0/15‐16 S2(config‐if‐range)# switchport mode access S2(config‐if‐range)# switchport access vlan 3 S1(config‐if‐range)# spanning‐tree portfast S2(config‐if‐range)# no shutdown S2(config‐if‐range)# int range f0/17‐18 S2(config‐if‐range)# switchport mode access S2(config‐if‐range)# switchport access vlan 255 S1(config‐if‐range)# spanning‐tree portfast S2(config‐if‐range)# no shutdown S2(config‐if‐range)# int range f0/21‐22 S2(config‐if‐range)# switchport mode access S2(config‐if‐range)# switchport access vlan 99 S1(config‐if‐range)# spanning‐tree portfast S2(config‐if‐range)# no shutdown S2(config‐if‐range)# end S2# show vlan brief Task 4 – Configure Etherchannel on switches On Switch 1 (S1): The following info will be configured for Etherchannel on S1: ‐
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Portchannel1 (Po1) o F0/1, F0/2, F0/3, F0/4 Portchannel2 (Po2) o F0/23, F0/24 S1# configure terminal S1(config)# int range f0/1‐4 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# channel‐group 1 mode active S1(config‐if‐range)# int range f0/23‐24 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# channel‐group 1 mode active S1(config‐if‐range)# end S1# show etherchannel summary On Switch 2 (S2): The following info will be configured for Etherchannel on S2: ‐
Portchannel1 (Po1) o F0/1, F0/2, F0/3, F0/4 S1# configure terminal S1(config)# int range f0/1‐4 S1(config‐if‐range)# switchport mode access S1(config‐if‐range)# channel‐group 1 mode active S1(config‐if‐range)# end S1# show etherchannel summary Task 5 ‐ Configure Bonding interface on Mikrotik RB On Mikrotik RB: Create new bonding interface for ether3 and ether4 as below: Task 6 ‐ Enable RSTP for both switches and assign root bridge On Switch 1 (S1): Enable RSTP spanning‐tree and set this switch to be root primary. S1# configure terminal S1(config)# spanning‐tree mode rapid‐pvst S1(config)# spanning‐tree vlan 2‐3,98‐99,255 root primary S1(config)# exit S1# show spanning‐tree vlan 2 On Switch 2 (S2): Enable RSTP spanning‐tree S2# configure terminal S2(config)# spanning‐tree mode rapid‐pvst S2(config)# exit S2# show spanning‐tree vlan 3 Task 7 – Configure Trunk ports On Switch 1 (S1): Configure trunk port for Po1 and Po2. S1# configure terminal S1(config)# int port‐channel 1 S1(config‐if)# switchport mode trunk S1(config‐if)# switchport trunk native vlan 98 S1(config‐if)# no shutdown S1(config‐if)# int port‐channel 2 S1(config‐if)# switchport mode trunk S1(config‐if)# switchport trunk native vlan 98 S1(config‐if)# no shutdown S1(config‐if)# end S1# show int trunk On Switch 2 (S2): Configure trunk port for Po1. S2# configure terminal S2(config)# int port‐channel 1 S2(config‐if)# switchport mode trunk S2(config‐if)# switchport trunk native vlan 98 S2(config‐if)# no shutdown S2(config‐if)# end S2# show int trunk Task 8 – Create sub‐interfaces for VLANs on Mikrotik RB On Task 5, we have already created a bonding interface on Mikrotik RB which combined two slave interfaces, ehter3 and ether4 and named that bounding interface as bonding‐vlan‐route. Just to recall that VLANs have been created but they are still unable to communicate each other. Therefore, to allow those VLANs communicate with each other, we will need to do Inter‐VLAN routing on Mikrotik RB as the following: ‐
Create VLAN 2, 3, 98, 99, 255 on Mikrotik RB on interface bonding‐vlan‐route. Assign IP addresses to VLAN interfaces on Mikrotik RB: Let see routing table on Mikrotik RB: Now you can try to make ping between VLANs Task 9 – Configure DHCP on Mikrotik RB for all VLANs Create IP pool for VLAN 2, 3, and 99 as below: Enable DHCP server as below: After finishing the Task 9, all PCs for each VLAN will be able to get IP address from the DHCP server which is running on Mikrotik RB. Task 10 ‐ Challenging Problem (How to offer IP addresses to all VLANs by using DHCP server which is not running on Mikrotik RB) The below diagram has designed to run DHCP server on Windows Server and DHCP running to Mikrotik RB was disable. ‐
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Disable DHCP server on Mikrotik RB and Enable DHCP Relay as below On DHCP Server which is running on windows server, we created three scope in order to offer the IP addresses to the following VLANs: 2, 3, and 99. o 192.168.2.10 – 192.168.2.200 for VLAN 2 o 192.168.3.10 – 192.168.3.200 for VLAN 3 o 192.168.1.10 – 192.168.1.200 for VLAN 99 Unfortunately, it does not work. All VLANs could not receive IP address from DHCP server. Please help!!!