Okay this one has had me stumped for days on end, I've looked around the internet, I can hardly find coherent information pertaining to my problem and/or links to irrelevant information.

I have a very small network for demonstrative purposes - `2 routers - 2 switches (2 VLANS on each connected to a PC each).

I can get one VLAN connected to the second router on the alternate network but the other has problems even pinging to its default gateway.

On the switch I have:

VLAN20: IP Address - VLAN30: IP Address -

Each VLAN is connected to a PC.

I shall assume you can assume the PC IP scheme as it is very basic knowledge.

The commands entered on the switch are:

the link going to the router is using a trunk port allowing vlans of 1-100 FastEthernet 0/2 is using switchport access VLAN 20 FastEthernet 0/3 is using switchport access VLAN 30

The 0/2 connects to the main router as well as connects to the second router using OSPF but the 0/3 does not connect even though the IP scheme is correct, default gateway is correct.

I have searched through many commands on the switch but none seem to work.

**The switch CAN ping to the PC but the PC cannot ping out not even to the switch**

EDIT: I am using a layer 2 switch so ip routing will not work.

  • my suggestion is to start with posting run configs for all devices and a picture if available. as well sh int for each uplink and sh ip route. May 25, 2015 at 2:55
  • if you can post a picture of your layout so we fully understand the question
    – Manny265
    May 25, 2015 at 7:02

1 Answer 1


You need to make use of sub-interfaces on the router commonly known as router on a stick. This means that one connection to the router will have multiple IP addresses representing the IP addresses in these subnets. The switch will not be doing any routing,it will instead send the packets to the router which will then find the route and send data back to the switch in an encapsulated manner that will then send to the other VLAN. This is also called InterVLAN routing.

Very good tutorials by danscourses found them useful through out my CCNA training.

Also take note the link between router and switch is a trunk,take a look at this manual from CISCO.
Let me know if this was useful

  • Thank you, you've saved me a lot of hassle and stress, the problem I was having is I was interVLAN(ing) on the switch as well as on the router, giving the same ip address on the switch and router meaning that when I was trying to ping the router wasn't sure where to send the traffic to so it was failing every time. May 25, 2015 at 16:24

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