So, everything in the following topology is what I’ve currently built.

On my desk, I have an Integrated services Cisco 870 router, a Cisco 3750 Catalyst switch, and an Internet connection coming in from a WAN on a Class B subnet, a regular ADSL broadband connection with a Class C subnet (192.168.) and eventually (not in this post) a Cisco phone.

The requirement then is to have everything connected with the two internet connections coming in on the 870 router, separated by VLAN, which then feed the switch (allowing ports to be tagged to either vlan) and then ultimately to my laptop so I can access everything (including both internet connections).

The topology looks like this;

So the steps needed to make this work are;

1) Configure the Cisco 800 router to deliver a DHCP class-C scope (for my benefit only) on vlan1

2) Configure the Cisco 800 router to have two other vlans (remember the 870 has in effect, one port, the four can not be physically configured, you need to use vlans) to have each connection terminated on them.

3) Configure the switch so port 1 is a management port, and 2-3 are for each different connection.

4) terminate the internet connection coming in on the Thompson router on one vlan

5) terminate the second internet connection via a WAN coming in on the other vlan

Assuming the kit is blank, and we are starting from scratch;

ROUTER
router# configure terminal
router(config)# ip dhcp pool marios-dhcppool
router# network 192.168.100.0 255.255.255.0
router(config)# default-router 192.168.100.5
router# dns-server 192.168.100.5 8.8.8.8
router(config)# lease 9
router(config)# ip dhcp excluded-address 192.168.100.10 192.168.100.5
router# (config)# 

router# configure terminal
router(config)# int vlan1
router# (config) ip address 192.168.100.5 255.255.255.0
router(config)# no shut
router(config)# vlan 2
router(config-vlan)# name office
router(config)# int vlan2
router(config)# ip address dhcp
router(config)# vlan 3
router(config-vlan)# name secondarynetconnection
router# (config)#int vlan3
router(config)# ip address dhcp

Switch
switch# configure terminal
switch(config)# int vlan1
switch(config)# ip address 192.168.100.10 255.255.255.0
switch(config)# default-gateway 192.168.100.5
switch(config)# int FastEthernet1/0/1
switch(config-int)# switchport mode access
switch(config)# int FastEthernet1/0/2
switch(config-int)# switchport mode access
switch(config)# int FastEthernet1/0/3
switch(config-int)# switchport mode access
switch(config-int)# switchport mode vlan50
switch(config)# int FastEthernet1/0/4
switch(config-int)# switchport mode access
switch(config-int)# switchport mode vlan50