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Interface explanation in Nexus

Hi All,

Can somemone help me understand the speed coloun of the below output, It denotes "S" & "D" beside auto. I woud like to understand what it actually refers to.

switch# show interface brief

--------------------------------------------------------------------------------

Ethernet      VLAN   Type Mode   Status  Reason                   Speed     Port

Interface                                                                                            Ch #

--------------------------------------------------------------------------------

Eth2/1        --     eth  routed down    Administratively down      auto(D)      --

Eth2/2        --     eth  routed down    Administratively down      auto(D)      --

Eth2/3        --     eth  routed down    Administratively down      auto(S)      --

Eth2/4        1      eth  pvlan  down    Administratively down      auto(D)      --

Eth2/5        --     eth  routed down    Administratively down      auto(S)      --

Eth2/6        1      eth  access down    Link not connected        auto(D)     --

Eth2/7        1      eth  access up      none                              1000(S)     --

Eth2/8        --     eth  routed down    Administratively down      auto(D)      --

Eth2/9        1      eth  access up      none                              1000(D)     --

Thanks to all in advance!

Sagar

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Sh Interface brief explanation in Nexus

Hi Sagar,

Some I/O modules on the Nexus have over-subscribed capacity between the ports and the switch fabric e.g., the N7K-M132XP-12 has 320Gbps (32*10GE) worth of port capacity but only 80Gbps of switch fabric capacity, so an over-subscription of 4:1.

On these modules the way the capacity is shared is with the ports being split into a number of port-groups. On the aforementioned N7K-M132XP-12 module we have port groups with interfaces {1,3,5,7}, {2,4,6,8}, {9,11,13,15}, {10,12,14,16} etc., sharing the available fabric bandwidth. You're able to determine which ports are part of the same port-group with the show interface capabilities command and look for the line "Port Group Members" in the output.

For the M1 32 module the default operation is that the fabric bandwidth is shared between all members of the port-group, but the switch can be configured such that a single port of the group has full fabric capacity available to it i.e., the capacity is dedicated to that one port. This is configured using the rate-mode dedicated command within interface context. Note though that when this command is configured there's only one port of the group active so if you configure port 1 as dedicated then ports 3, 5 and 7 can no longer be used.

So what I think you're seeing in the show interfaces brief output is an indication of whether the interface is operating in Dedicated (D) and Shared (S) mode. Can you paste the output of the show interface capabilities | include "^Ethernet|Model|Port Group" and then we can see what I/O modules you have and so understand whether this is the case.

Regards

2 REPLIES

Sh Interface brief explanation in Nexus

Hi Sagar,

Some I/O modules on the Nexus have over-subscribed capacity between the ports and the switch fabric e.g., the N7K-M132XP-12 has 320Gbps (32*10GE) worth of port capacity but only 80Gbps of switch fabric capacity, so an over-subscription of 4:1.

On these modules the way the capacity is shared is with the ports being split into a number of port-groups. On the aforementioned N7K-M132XP-12 module we have port groups with interfaces {1,3,5,7}, {2,4,6,8}, {9,11,13,15}, {10,12,14,16} etc., sharing the available fabric bandwidth. You're able to determine which ports are part of the same port-group with the show interface capabilities command and look for the line "Port Group Members" in the output.

For the M1 32 module the default operation is that the fabric bandwidth is shared between all members of the port-group, but the switch can be configured such that a single port of the group has full fabric capacity available to it i.e., the capacity is dedicated to that one port. This is configured using the rate-mode dedicated command within interface context. Note though that when this command is configured there's only one port of the group active so if you configure port 1 as dedicated then ports 3, 5 and 7 can no longer be used.

So what I think you're seeing in the show interfaces brief output is an indication of whether the interface is operating in Dedicated (D) and Shared (S) mode. Can you paste the output of the show interface capabilities | include "^Ethernet|Model|Port Group" and then we can see what I/O modules you have and so understand whether this is the case.

Regards

New Member

Interface explanation in Nexus

Ethernet3/1

Model: N7K-M132XP-12L

Type (SFP capable): 10Gbase-(unknown)

Speed: 10000

Duplex: full

Trunk encap. type: 802.1Q

Channel: yes

Broadcast suppression: percentage(0-100)

Flowcontrol: rx-(off/on),tx-(off/on)

Rate mode: dedicated/shared

QOS scheduling: rx-(8q2t),tx-(1p7q4t)

CoS rewrite: yes

ToS rewrite: yes

SPAN: yes

UDLD: yes

Link Debounce: yes

Link Debounce Time: yes

MDIX: no

Pvlan Trunk capable: yes

Port Group Members: 1,3,5,7

TDR capable: no

FabricPath capable: no

Port mode: Routed,Switched

FEX Fabric: yes

dot1Q-tunnel mode: yes

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