How do I Configuring multiple VLANS on a Catalyst 5000 to use seperate uplinks to a 2600 router

Posted on 2005-05-09
Last Modified: 2008-03-17
I have a Catalyst 5000 with 1 supervisor module, and 4 12 port ethernet modules.

I have created 4 separate vlans using ports 1/1-12, 2/1-12, 3/1-12, and 4/1-12

How would I go about setting port 1/1, 2/1,3/1, and 4/1 as seperate uplinks for all hosts within those vlans. My goal is to have the Catalyst 5000 act as 4 seperate switches which all link to my 2600 router for access-lists and routing between the 4 VLANS.

Also, would it be possible to have all the VLANS use a single port for the uplink to the router and how would that be configured.

For my router, I have 4 ethernet interfaces that connect to ports 1/1, 2/1, 3/1, and 4/1 with the following ip's:

Each host within the corresponding VLAN has an ip in the same network. I.e if the host was in VLAN 1 it would have an ip in the range.

Question by:jcc05
    LVL 27

    Expert Comment

    Yes, you could use a single uplink - turning your router into a "one armed router" so that all four vlans would pass through 1 link.  I think it would depend on your code - but you would use 802.3q VLAN trunking and make both ports tagged so that that traffic from VLAN1 would be tagged and so on.  On the router, you'd have that port tagged as well and the interface would have 4 subinterfaces on it with different IP's.
    LVL 28

    Accepted Solution

    Unless your switch and router code is very current, you'll need to use ISL trunking. On the switch you simply turn trunking on on the desired port. Only 100Mb ports do ISL trunking though so hopefully your router qualifies.
    set trunk 1/1 on isl

    The switch will automatically trunk all configured vlans unless you prune them. On the router you would do the following, assuming that the vlans are 2,3,4 & 5 (bad idea to use 1 for traffic):

    interface fasthernet 0/0
     no shut
    interface fastethernet 0/0.2
     encapsulation isl 2
     ip address
    interface fastethernet 0/0.3
     encapsulation isl 3
     ip address
    interface fastethernet 0/0.4
     encapsulation isl 4
     ip address
    interface fastethernet 0/0.5
     encapsulation isl 5
     ip address

    The subinterface number is arbitrary, but the encapulation number is the VLAN number.
    LVL 11

    Expert Comment

    Some newer Cisco 5000 10/100 blades support 802.1q trunking as an alternative to ISL.  Some recent Cisco routers support only 802.1q and not ISL.  (We learned this the hard way; you could get lucky.)

    Note that you could probably buy four 2912XLs for less than the 5000 cost.  Using VLANs *just* to make a big switch act as several small switches is not a cost-effective approach.  It's when you add trunking that you start to see some payoff from VLANs.

    LVL 28

    Expert Comment

    As I said, the ROUTER may not support 802.1q. But if it's a 2600, it definitely supports ISL on a 100mb interface. And the switch you have definitely will too. It was Cisco's pre-802.1q trunking protocol, and all the 5000s will do it.

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    Highfive Gives IT Their Time Back

    Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

    It happens many times that access list (ACL) have to be applied to outgoing router interface in order to limit some traffic.This article is about how to test ACL from the router which is not very intuitive for everyone. Below scenario shows simple s…
    Problem Description:   Couple of months ago we upgraded the ADSL line at our branch office from Home to Business line. The purpose of transforming the service to have static public IP’s. We were in need for public IP’s to publish our web resour…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

    794 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    18 Experts available now in Live!

    Get 1:1 Help Now