https://www.cybrary.it/video/layer3-ip-routing-lab/

Doing some inter-VLAN routing between SW8 and R2.

PC Network Netmask VLAN
PC1 10.10.10.1 255.255.255.0 VLAN 10
PC2 10.10.10.2 255.255.255.0 VLAN 10
PC3 20.20.20.3 255.255.255.0 VLAN 20
PC4 20.20.20.4 255.255.255.0 VLAN 20

Configure SW8

Create VLANs:

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# VLAN 10
sw8 (config)# vlan 10
sw8 (config-vlan)# vlan acct.

# VLAN 20
sw8 (config)# vlan 20
sw8 (config-vlan)# vlan sales
sw (config-vlan)# exit

# Check
sw8 (config)# do show vlan brief

Put PCs into VLANs:

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# Configure port 1 and 2
sw8 (config)# interface range fastEthernet 0/1-2
sw8 (config-if-range)# switchport mode access
sw8 (config-if-range)# switchport access vlan 10

# Configure port 3 and 4
sw8 (config)# interface range fastEthernet 0/3-4
sw8 (config-if-range)# switchport mode access
sw8 (config-if-range)# switchport access vlan 20
sw8 (config-if-range)# exit
sw8 (config)# do show vlan brief

Make ports go up

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sw8 (config)# interface fastEthernet 0/1-4

# Ports go directly to forwarding
sw8 (config-if-range)# spanning-tree portfast

# Save work
sw8 (config-if-range)# exit
sw8 (config)# wr

At this moment PC1 is not able to ping PC3 (due to different broadcast domains). The link between the switch (SW1) and the router (R2) will be a trunk link, since it allows to carry more than one VLAN.

Configure trunk port on the switch:

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sw8 (config)# interface fastEthernet 0/24
sw8 (config-if)# switchport trunk encapsulation dot1q
sw8 (config-if)# switchport mode trunk

# Turn off DTP (no negotiate), Routers don't understand DTP anyway
sw8 (config-if)# no negotiate
sw8 (config-if)# do show interface fastEthernet switchport

Now the switch side is alsmost done. We’ll have to specify which VLANs should be allowed on a port:

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sw8 (config)# interface fastEthernet 0/24

# Allow only VLAN 10 and VLAN 20
sw8 (config-if)# switchport trunk allowed vlan 10,20

# Check that
sw8 (config-if)# do show interface f0/24 switchport

Configure R2

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r2# conf t
r2 (config)# interface fastEthernet 0/1
r2 (config-if)# no shutdown
r2 (config-if)# no ip address
r2 (config-if)# description TRUNK_TO_SW8
r2 (config-if)# exit

No IP address since we are going to create sub-interfaces.

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### Sub-interface to carry VLAN 10
r2 (config)# interface fastEthernet 0/1.10
r2 (config)# do show ip interface brief

# Assign last IP address (will generate error)
r2 (config)# ip address 10.10.10.254 255.255.255.0
% Configuring IP routing on a LAN subinterface is only allowed if that  subinterface is already configured as part of an IEEE 802.10, IEEE 802.1q or  ISL VLAN.

# Set encapsulation to dot1q and assign again the IP address
r2 (config)# encapsulation dot1q 10
r2 (config)# ip address 10.10.10.254 255.255.255.0


### Sub-interface to carry VLAN 20
r2 (config)# interface fastEthernet 0/1.20
r2 (config-subif)# encapsulation dot1q 20
r2 (config-subif)# ip address 20.20.20.254 255.255.255.0

Check settings:

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r2 (config)# show ip interface brief

Set default gateway

We’ll still have to setup the default gateway (GW) for the PCs.

PC Default gateway
PC1 10.10.10.254
PC2 10.10.10.254
PC3 20.20.20.254
PC4 20.20.20.254

Now PC1 should be able to ping PC3. First check if R2 has both networks in its IP routing table:

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r2# show ip route

Show of sub-interface:

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r2# show interfaces f0/1.1