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Native Backbone Traffic

Will data transfers stay local to a non-core switch when running  native IOS?

  • SW1 - SUP32-10G acting as core with SVI's and OSPF
  • SW2 and SW3 - SUP32-10G's essentially acting as L2 distribution  devices
  • Uplinks via 10G multi-mode fiber

If host A needs to download 15gigs of data from host B  and they are both on SW2, will all the traffic pass through the core  switch, or just the initial lookup until cached on SW2? With CATOS and  MLS the traffic would stay local to SW2. Similary if host A was on S2  and host b on SW3.

4 REPLIES
Hall of Fame Super Blue

Re: Native Backbone Traffic

Mikamus07 wrote:

Will data transfers stay local to a non-core switch when running  native IOS?

  • SW1 - SUP32-10G acting as core with SVI's and OSPF
  • SW2 and SW3 - SUP32-10G's essentially acting as L2 distribution  devices
  • Uplinks via 10G multi-mode fiber

If host A needs to download 15gigs of data from host B  and they are both on SW2, will all the traffic pass through the core  switch, or just the initial lookup until cached on SW2? With CATOS and  MLS the traffic would stay local to SW2. Similary if host A was on S2  and host b on SW3.

Are host A and B in the same vlan ?

If they are then traffic should stay local to SW2. If they aren't then traffic will have to go via the L3 vlan interface on SW1.

As for A on SW2 and B on SW3. If the disrtibution switches are interconnected to each other with a L2 trunk and A & B are in same vlan then traffic will not have to go via core switch. If they are in different vlan then traffic will have to go via core switch.

It all depends on whether the traffic an be switched ie. they are in the same vlan or routed ie. they are in different vlans.

Jon

Re: Native Backbone Traffic

I believe If both hosts are on the same switch, in the same broadcast domain (vlan) then the MSFC will take of that locally since the switch got the MAC addresses in it  CAM table,, no need to get the  Core switch involved..

Hall of Fame Super Blue

Re: Native Backbone Traffic

francisco_1 wrote:

I believe If both hosts are on the same switch, in the same broadcast domain (vlan) then the MSFC will take of that locally since the switch got the MAC addresses in it  CAM table,, no need to get the  Core switch involved..

Francisco

If the 2 devices are in the same subnet then the MSFC shouldn't come into it at all because the MSFC is concerned with L3 lookups not L2.

Jon

Re: Native Backbone Traffic

Jon,

Actually there is something else i need to ask you regarding this subject offline.

Can you please send me your email address.

My email is franco.isaac@btinternet.com.

Thanks

Francisco

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