# 4506 backplane bandwidth

May 9th, 2008

in case of 48port modules, there are groups of 8 ports that share common bw toward backplane of switch. In case of 4506 it is 1G limit. Does this limit apply in case of traffic between ports in same group?

Correct Answer by Sushil Kumar Katre about 8 years 5 months ago

Hi,

Let's take an example to understand this -

Assuming that you have "WS-X4448-GB-RJ45" 48 port line card.

Bandwidth is allocated across six 8-port groups, providing 1 Gbps per port group.

This means there is an ASIC per 8 GE interfaces connecting to the switch fabric over 1Gbps connectivity.

Now in order to understand how thi sis going to effect, let's consider following scenarios -

1) trafic flow betweeen port1 and port2 of same group - The traffic does not need to go through the 1Gbps pipe. NO RESTRICTION.

2) traffic flow between port1 and port2 of different group - this traffic would flow through the 1 Gbps pipe.

3) traffic flow between port1 and port2 of two different line cards on the same switch - same as scenario 2.

4) traffic flow between port1 and another switch - same as scenario 2.

-> Sushil

Overall Rating: 5 (1 ratings)

## Replies

Sushil Kumar Katre Sat, 05/10/2008 - 01:22

Hi,

Let's take an example to understand this -

Assuming that you have "WS-X4448-GB-RJ45" 48 port line card.

Bandwidth is allocated across six 8-port groups, providing 1 Gbps per port group.

This means there is an ASIC per 8 GE interfaces connecting to the switch fabric over 1Gbps connectivity.

Now in order to understand how thi sis going to effect, let's consider following scenarios -

1) trafic flow betweeen port1 and port2 of same group - The traffic does not need to go through the 1Gbps pipe. NO RESTRICTION.

2) traffic flow between port1 and port2 of different group - this traffic would flow through the 1 Gbps pipe.

3) traffic flow between port1 and port2 of two different line cards on the same switch - same as scenario 2.

4) traffic flow between port1 and another switch - same as scenario 2.

-> Sushil

dragec Sat, 05/10/2008 - 02:11

ok, thanks, scenario 1 was what I was interested about.

joseph.derrick Sun, 05/11/2008 - 00:02

Hi Sushil,

Is there a way to check what ports belong to a certain group ? Is there also a way to check on the bandwidth utilization utilized by a certain group in the backplane ?

Thanks,

Joseph Derrick

Sushil Kumar Katre Sun, 05/11/2008 - 02:52

Hi Joseph,

There must be some commands available. But I am not really aware of those commands.

May be someone else can provide some information on this.

-> Sushil

draganskundric Fri, 11/06/2009 - 00:39

long time no see, but I you sure on your answer. I have info for Cisco representative that even if traffic goes between tw ports in sam group, 1G backplane limit applies.

br

Giuseppe Larosa Fri, 11/06/2009 - 06:00

Hello Dragan,

I can confirm this we have seen the limit during performance tests on a server.

in other words no additional local switching capabilities are available.

Hope to help

Giuseppe

iyde Fri, 11/06/2009 - 13:09

Right, there's no such thing as local switching in Cat4500, opposite of Cat6500. All switching is done by the supervisor which also includes traffic between two ports on same line card and on same ASIC on that line card.

HTH, Ingolf