8 Replies Latest reply: Nov 19, 2010 8:59 AM by gary rivers RSS

    enabling IP Routing on a 3560 SW

    gary rivers

      I installed a 3560 SW with the thoughts that eventually it would be a L3 SW but for right now it would be just an L2  SW.  So I did not enable IP Routing.

      That was a big mistake!  i should have enabled ip routing anyway but hind-sight.

      so here i am, i have several devices connected to this SW and they are all on VLAN 1 and i want to connect a different network to the switch.  Therefore i need to enable ip routing and eigrp.

      So my question is, WHEN i do that, will the connected devices lose connectivity while the SW learns new routes, etc?  or will the devices keep connectivity and never know the difference?


      Thanks, Gary

        • 1. Re: enabling IP Routing on a 3560 SW
          Aaron Cary

          Thats not quite what a layer 3 switch does. It truly provides you the availability to do inter-vlan routing without the use of an actual router, and also allows you to do default routes for additional connectivity. Take a look at the configuration provided by Cisco. I can guarantee that they dont support routing protocols like eigrp.



          • 2. Re: enabling IP Routing on a 3560 SW

            Aaron, before I try to refute one of your statements, did I read correctly that you say that 3560s do not support EIGRP?


            I would then recommend you take a look at this: http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5528/product_data_sheet09186a00801f3d7d.html


            Then do a search for "High-Performance IP Routing".  I'll provide a snippet for review:


            • Cisco Express Forwarding hardware routing architecture delivers extremely high-performance IP routing.

            • Basic IP unicast routing protocols (static, RIPv1, RIPv2 and RIPng) are supported for small-network routing applications.

            •  Advanced IP unicast routing protocols (OSPF, Interior Gateway Routing  Protocol [IGRP], EIGRP, Border Gateway Protocol Version 4 [BGPv4] and  IS-ISv4) are supported for load balancing and constructing scalable  LANs. The IP Services license is required.

            • IPv6 routing capability (OSPFv3, EIGRPv6) is support. IP Services license is required.

            • Policy-Based Routing (PBR) allows superior control by enabling flow redirection regardless of the routing protocol configured.

            • Inter-VLAN IP routing provides for full Layer 3 routing between two or more VLANs.

            •  Protocol Independent Multicast (PIM) for IP Multicast routing is  supported, including PIM sparse mode (PIM-SM), PIM dense mode (PIM-DM),  and PIM sparse-dense mode. The IP Services license is required.

            • Fallback bridging forwards non-IP traffic between two or more VLANs.



            I've used 3560s as the sole device at sites when necessary, supporting a broad range of technologies. They are also a mainstay in the CCIE R&S lab because of their incredible flexibility and extended capabilities.




            Gary - as for turning up ip routing on the 3560, and adding new networks, I strongly recommend doing so during an approved maintenance window.  You do indeed run the risk of losing connectivity momentarily as the switch implements new protocols/related tables, and rebuilds it's view of the network.   I would not expect a major outage but doing it in a maintenance window is a prudent measure in my opinion.


            The bigger question - do you need IP Routing enabled, or do you just need to add a VLAN and a trunk?  Do you have router on a stick or is this the only device with that kind of functionality in this topology?

            • 3. Re: enabling IP Routing on a 3560 SW
              gary rivers

              well, I'm just assuming that I need it enabled.

              Network Overview8.png

              in the diagram, i want to move the two networks off of the KWCHRTR to the 3560 SW (sw27).

              Eventually, i want to remove the RTR all together.

              • 4. Re: enabling IP Routing on a 3560 SW
                Aaron Cary

                Thanks Travis. I stand very corrected. I did not think they could go that far up the chain. Guess I will be looking at some CCNP courses in the future after my Voice studies.

                • 5. Re: enabling IP Routing on a 3560 SW

                  What kind of demarc do you have from your ISP?  RJ45 ethernet?  Are you doing default route out?  Are you terminating any voice services on the router, or VPNs?

                  • 6. Re: enabling IP Routing on a 3560 SW

                    No worries Aaron!  Just want to make sure the right information makes its way out there to everyone :-)

                    • 7. Re: enabling IP Routing on a 3560 SW
                      Aaron Cary


                      • 8. Re: enabling IP Routing on a 3560 SW
                        gary rivers

                        the ISP comes in on a cable modem so it's just an RJ45. No voice terminations.

                        default route: Right now the RTR is the default gateway so what i thought i'd do is move the two networks over to the SW, make sure they can talk, etc and then move the ASA connection.  And then shutdown the RTR and re-IP the SW the RTR's IP.