2

I am trying to simulate a network, I am having problem directing traffic to exit the L3 Switch and to go to router for routing to outside network. (I don't want to use routing capability of switch, other than just setting a default route or something...)

Long Description:

enter image description here

Now,I understand there is a way to do this by making the L3 Switch do the routing, but I don't want that to happen. I want the L3 switch to route only the VLAN traffic among the VLANs it holds. All the other foreign traffic by default should be handed over to the router for routing. Is there a way this can be done withouthaving to input all routes of the foreign network in the routing table of L3 Switch.

4
  • You could use a default route. Why do you think this isn't using the routing capability of the switch? It is routing if it routes between the VLANs, but according to the diagram, it shouldn't be routing since the routing is happening on the router, and you are trunking to the switch. You should edit the question to include the router and switch configurations.
    – Ron Maupin
    May 29, 2016 at 17:36
  • It's not clear to me what you're trying to do. If you don't want the switch to route, then you need to trunk all the VLANs to the router. If you want the switch to route between VLANs, then you need a default route on the switch that points to the router.
    – Ron Trunk
    May 30, 2016 at 0:03
  • @Ron Maupin, I understand that my question was very poorly described. And I will include the configurations from my next question. I will try to rephrase it again. I wanted the L3 switch to only route among the vlans and send any packet meant for any other network directly(by default) to the switch. I wanted to know in how many methods can we do this. If you could please elaborate more on this, tell me the pros and cons of using a particular method. I would be grateful.
    – cRAYonhere
    May 30, 2016 at 6:35
  • @Ron Trunk I understand that my question was very poorly described. I will try to rephrase it again. I wanted the L3 switch to only route among the vlans and send any packet meant for any other network directly(by default) to the switch. I wanted to know in how many methods can we do this. If you could please elaborate more on this, tell me the pros and cons of using a particular method. I would be grateful.
    – cRAYonhere
    May 30, 2016 at 6:36

2 Answers 2

1

I wanted to know in how many methods can we do this. If you could please elaborate more on this, tell me the pros and cons of using a particular method.

There are essentially two methods:

  • You configure static routes on the switch for all subnets not connected to the switch.
  • You configure a routing protocol so that the switch and router can exchange routing information.

For each method, you have a choice of using a default route or configuring/advertising all the known routes.

A default route makes the most sense, since a full Internet routing table is over 500,000 routes. More importantly, your switch needs to only make a simple routing decision: is the destination locally connected or not? There is no need for additional routing information.

Whether you configure a static default route or have the router advertise the default route via a routing protocol is up to you.

0
2

You'll need four SVIs (VLAN interfaces) on the switch to achieve what you're after. The SVIs are as follows:

  • VLAN 2
  • VLAN 3
  • VLAN 4
  • VLAN 100 (or any other number of your choosing)

The first three VLANs allow the switch to perform routing for these three VLANs. The fourth VLAN is used for routing between the switch and the router. Through this VLAN you will need to configure a default route on the switch witch points to the router's IP address as the next hop address.

Note that instead of using VLAN 100 you could issue the "no switchport" command on the switch's gi0/1 interface and use it as a layer 3 interface instead.

3
  • Thank you @OzNetNerd , even though my description was kinda hazy. You caught my point. I used the second method of "no switchport" and it works perfectly. Can you please elaborate how willl the default route thing work, if it's not a problem. Thanks again.
    – cRAYonhere
    May 30, 2016 at 6:28
  • No worries at all @cRAYonhere. Can you please provide more information on what it is you don't understand about default routes? Also, can you please let me know what addresses you've used for the link between the switch and the router?
    – OzNetNerd
    May 31, 2016 at 23:11
  • I have shared the link to the packet tracer file for all the configurations, incase you want to see only the ips' assigned, I have attached a .png file link also. Attachments .pkt .png
    – cRAYonhere
    Jun 2, 2016 at 13:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.