Bandwidth of SVI

Unanswered Question
Apr 7th, 2008

It appears to be a simple question, but I cannot get a clear answer:

What is the bandwidth of an SVI interface on a cat6500?



I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 2.3 (5 ratings)
Istvan_Rabai Mon, 04/07/2008 - 04:22

Hi Marcel

You can check it by using the "show interface vlan x" command.

For me it showed 1000000kbits per second (1 Gbps) on a 6509 and a 4948.



mvandorp Mon, 04/07/2008 - 04:29

This is the administrative bandwidth, used by eg OSPF and EIGRP to make routing decisions.

I mean the real bandwidth, or speed (as used with real ethernet), or clock rate (used with serial lines).

That administrative BW can be changed with the interface command: bandwidth [1..10000000]


Istvan_Rabai Mon, 04/07/2008 - 04:38

Hi Marcel,

This is true, it is the administrative bandwidth.

Physically you can be connected to a Fastethernet, Gigabitethernet or a Tengigabitethernet interface. The physical connection will give you the real bandwith you can have.



Richard Burts Mon, 04/07/2008 - 04:51


I believe that there is a logical fallacy in your question. You ask:

"I mean the real bandwidth, or speed (as used with real ethernet), or clock rate (used with serial lines)."

but real bandwidth (or real speed) exists only on physical interfaces. A SVI is a virtual interface and as such does not have a real bandwidth. If anything the bandwidth of a SVI is the bandwidth of the backplane of the switch.



mvandorp Mon, 04/07/2008 - 07:35

True, but I did not want to influence your answers.

What I've learned from several documents on CCO, that an SVI is using the backplane. On a cat6500 this is a 6 Gbps EtherChannel.

Is the folllowing correct:

All SVIs share the available bandwidth of 6 Gbps of the backplane.

The thing I try to get clear is related to the following configuration:

I have an FWSM in the cat6500, with multiple virtual firewalls. At this moment each outside interface of the firewall has it's own SVI on the router.

If I combine all outside interfaces on one SVI (all outsides are in the same L3 subnet), does this impact the available bandwidth?

How about SVI-SVI traffic, and FW-FW traffic?

As you can see, there is no physical port involved. The physical ports are all behind the firewalls.

I know I can configure QoS on the different FW-contexts, but this question is about the bandwidth on the router (or MSFC).

Looking forward to your insights!



This Discussion