[c-nsp] Line-rate on catalyst swiches
Shanawaz Batcha
ismath.shaan at gmail.com
Tue Jul 23 22:49:32 EDT 2013
I am trying to understand how line-rate works on catalyst switches.
Lets assume I have a WS-2960G-48 model switch. The advertised backplane
capacity for this platform is 32G. That is 32Gbps for 48 ports, so I assume
straightaway that its a blocking (as in not-non-blocking) switch
sw1#sh platform pm if-numbers
interface gid gpn lpn port slot unit slun port-type lpn-idb gpn-idb
----------------------------------------------------------------------
Gi0/1 1 1 1 5/3 1 1 1 local Yes Yes
Gi0/2 2 2 2 5/0 1 2 2 local Yes Yes
Gi0/3 3 3 3 5/1 1 3 3 local Yes Yes
Gi0/4 4 4 4 5/2 1 4 4 local Yes Yes
Gi0/5 5 5 5 4/2 1 5 5 local Yes Yes
Gi0/6 6 6 6 4/3 1 6 6 local Yes Yes
Gi0/7 7 7 7 4/0 1 7 7 local Yes Yes
Gi0/8 8 8 8 4/1 1 8 8 local Yes Yes
Gi0/9 9 9 9 7/3 1 9 9 local Yes Yes
Gi0/10 10 10 10 7/0 1 10 10 local Yes Yes
Gi0/11 11 11 11 7/1 1 11 11 local Yes Yes
Gi0/12 12 12 12 7/2 1 12 12 local Yes Yes
Gi0/13 13 13 13 6/2 1 13 13 local Yes Yes
Gi0/14 14 14 14 6/3 1 14 14 local Yes Yes
Gi0/15 15 15 15 6/0 1 15 15 local Yes Yes
Gi0/16 16 16 16 6/1 1 16 16 local Yes Yes
Gi0/17 17 17 17 3/3 1 17 17 local Yes Yes
Gi0/18 18 18 18 3/0 1 18 18 local Yes Yes
Gi0/19 19 19 19 3/1 1 19 19 local Yes Yes
Gi0/20 20 20 20 3/2 1 20 20 local Yes Yes
Gi0/21 21 21 21 2/2 1 21 21 local Yes Yes
Gi0/22 22 22 22 2/3 1 22 22 local Yes Yes
Gi0/23 23 23 23 2/0 1 23 23 local Yes Yes
Gi0/24 24 24 24 2/1 1 24 24 local Yes Yes
Gi0/25 25 25 25 9/3 1 25 25 local Yes Yes
Gi0/26 26 26 26 9/0 1 26 26 local Yes Yes
Gi0/27 27 27 27 9/1 1 27 27 local Yes Yes
Gi0/28 28 28 28 9/2 1 28 28 local Yes Yes
Gi0/29 29 29 29 8/2 1 29 29 local Yes Yes
Gi0/30 30 30 30 8/3 1 30 30 local Yes Yes
Gi0/31 31 31 31 8/0 1 31 31 local Yes Yes
Gi0/32 32 32 32 8/1 1 32 32 local Yes Yes
Gi0/33 33 33 33 1/3 1 33 33 local Yes Yes
Gi0/34 34 34 34 1/0 1 34 34 local Yes Yes
Gi0/35 35 35 35 1/1 1 35 35 local Yes Yes
Gi0/36 36 36 36 1/2 1 36 36 local Yes Yes
Gi0/37 37 37 37 0/2 1 37 37 local Yes Yes
Gi0/38 38 38 38 0/3 1 38 38 local Yes Yes
Gi0/39 39 39 39 0/0 1 39 39 local Yes Yes
Gi0/40 40 40 40 0/1 1 40 40 local Yes Yes
Gi0/41 41 41 41 11/3 1 41 41 local Yes Yes
Gi0/42 42 42 42 11/0 1 42 42 local Yes Yes
Gi0/43 43 43 43 11/1 1 43 43 local Yes Yes
Gi0/44 44 44 44 11/2 1 44 44 local Yes Yes
Gi0/45 45 45 45 10/3 1 45 45 local Yes Yes
Gi0/46 46 46 46 10/2 1 46 46 local Yes Yes
Gi0/47 47 47 47 10/1 1 47 47 local Yes Yes
Gi0/48 48 48 48 10/0 1 48 48 local Yes Yes
I presume from the above outputs that are 12 asics of 4 ports each.
1) Does traffic within the ASIC hit the backplane and count towards the
backplane 32 gbps capacity? Does say traffic from port Gi0/29 to Gi0/30
(both in Asic 8) reach the backplane or simply switched locally at ASIC
level?
2) If the answer to the above is yes, and assuming all ports are
transmitting at the same time at 1 Gbps, then presumably we can call this
a line-rate switch provided the right connections are in the right places?
if the answer is no, and assuming all ports are transmitting at the same
time at 1 Gbps, then there will be about ~16 gbps worth of drops?
Thanks,
Shan
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