topic using SVI with Layer3 Port in Switching

using SVI with Layer3 Port

pattymick54 — Fri, 08 Mar 2019 13:12:07 GMT

I have an older switch which does not support Layer3 Ports (routed port). can I connect this switch using an SVI with another switch where the interface is configured as a routed port ?

I guess the best bet is to

Carlos Villagran — Sun, 03 Apr 2016 18:50:07 GMT

I guess the best bet is to configure that routed port as a trunk in order to connect both switches since it will not even work if the switch does not have L3 capabilities since it would not be able to route packets through that interface.

Hope it helps, best regards!

Thanks Carlos,

pattymick54 — Sun, 03 Apr 2016 19:02:47 GMT

Thanks Carlos,

Both switches have layer3 capabilities, It's just that one can only be configured with SVI does not have support for the Layer3 port "routed port" . So, on the core switch (the switch that supports "routed port") I wondering if I could configure the interface as Layer3 and on the access switch configure an SVI, configure the interface to the Core as an access port in that vlan.

Basically, as I would if configuring a Layer3 switch connection with a router.

Sure, you can. You configure

Reza Sharifi — Sun, 03 Apr 2016 21:17:42 GMT

Sure, you can. You configure one switch as routed port and the other switch with an SVI and the physical port configured as access port.

So, the IP on the routed port is configured on the physical interface and the IP for the other switch is configured on the SVI.

HTH

Hi!

Carlos Villagran — Sun, 03 Apr 2016 23:03:40 GMT

Hi!

No, you will definetely need to make that routed port a trunk port in order to hosts in both switches to communicate. Since the routed interface is creating a line in the routing table, every host in the same vlan as the switch with the routed interface will never take the path to the routed interface.

In order to reach other hosts via the routed interface a static route would need to be created taking the routed interface as next hop, however when the frame reaches the next hop switch (because it will reach it actually) the other switch will never know how to answer since you cannot create a static route for L2 interfaces (nor Routing protocols will form adjacencies).

Hope it helps, best regards!

Hi Reza, Do you know of a

pattymick54 — Mon, 04 Apr 2016 13:33:04 GMT

Hi Reza, Do you know of a cisco document or book that describes this design?

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Joseph W. Doherty — Mon, 04 Apr 2016 14:56:37 GMT

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I agree with Reza. In fact, for quick manual fail over on some stacked or chassis L3 switches, rather than using a "routed" port, I define two ports in a VLAN and use a SVI. That way, if the switch's member or line card hosting the active port being routed fails, you can quickly just move the cable to the other VLAN member port.

BTW, on many Cisco switches, "routed" ports are still VLAN ports with SVIs, it's all just hidden from you (and some VLAN "stuff" is also automatically disabled on "routed" ports).

Thanks for the input Joseph.

pattymick54 — Mon, 04 Apr 2016 16:11:09 GMT

Thanks for the input Joseph. Part of he reason for using the routed port was because STP is disabled. But, the manual fail over is something to think about.

Thanks again,

Patty