More that 8 routed SVI:s

Unanswered Question
Dec 11th, 2008

We have a few catalyst 3550/3560/3750 and as far as I know they only support 8 routed SVI:s each.

Although it is possible to create more than 8 SVI:s, it is not supported by Cisco. I would like to reduce these switches to two or three, thus increasing the number of SVI:s om each switch. What other Catalyst switch supports more than 8 routed SVI:s? I know that 4500 series and 6500 series catalysts will do the job, but do Cisco have other L3 switches?

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mattias04 Fri, 12/12/2008 - 11:35

Well, the size of the TCAM is finite, and to many SVI:s will indeed affect perfomance.

So, to summarize:

We need to use Cat 4500 or 6500 to use more than 8 routed SVI:s and still have a supported configuration.

Is this correct?

Regards

Edison Ortiz Fri, 12/12/2008 - 12:10

Mattias,

Can you provide a link where it states the limit is 8?

Based on the 3560 documentation:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_46_se/configuration/guide/swiprout.html

A Layer 3 switch can have an IP address assigned to each routed port and SVI. The number of routed ports and SVIs that you can configure is not limited by software. However, the interrelationship between this number and the number and volume of features being implemented might have an impact on CPU utilization because of hardware limitations. To optimize system memory for routing, use the sdm prefer routing global configuration command.

HTH,

__

Edison.

mattias04 Sat, 12/13/2008 - 06:20

Hi ediortiz,

thanks for your reply!

This is what the sdm template says for Catalyst 3550/3560/3750 and I think this can be found elsewhere in the Cisco documentation.

Here is one link:

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a00801e7bb9.shtml

And here is the output from one c3550:

ro01-ipa#sh sdm prefer

The current template is the default template.

The selected template optimizes the resources in

the switch to support this level of features for

8 routed interfaces and 1K VLANs.

number of unicast mac addresses: 5K

number of igmp groups: 1K

number of qos aces: 1K

number of security aces: 1K

number of unicast routes: 8K

number of multicast routes: 1K

ro01-ipa#

I've read somewhere on the net (can't remember the forum) that using more than 8 SVI:s (or routed ports) is not support on these Catalysts.

I might be wrong, but I need to know what configuration is supported by Cisco.

Edison Ortiz Sat, 12/13/2008 - 12:18

Mattias,

That's a very good observation. I've searched internally and I can't find a conclusive answer to this limitation.

What I've found is a suggestion to verify your CPU performance as soon as you go over the 8 routed interfaces limit. If the CPU maintains low %, then you should be fine.

With that said, you can create more than 8 routed ports in the router w/o receiving an error in the CLI. I was able to create 15 routed ports in the lab w/o seeing any performing issue nor receiving an error in the CLI.

HTH,

__

Edison.

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