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L2 Switch mode

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judyjoseph edited this page May 26, 2021 · 22 revisions

SONiC switches are normally operated in Layer 3 Switch mode, however, they could also be operated as L2 Switch. This document will describe the basic features supported in L2 Switch mode. (Note: This page needs to be updated for multi-asic devices like Nexus 3164 )

L2 Switch Configuration Workflow

1. Config the management port and hostname

Below is a sample command line. Please replace the eth0 and gwaddr values with correct management IP address and default gateway address.

cat <<EOF | sudo config reload /dev/stdin -y
{
    "MGMT_INTERFACE": {
        "eth0|10.3.147.46/23": {
            "gwaddr": "10.3.146.1"
        }
    },
    "DEVICE_METADATA": {
        "localhost": {
            "hostname": "sonic"
        }
    }
}
EOF

If dual ToR configuration is required, use the following example:

cat <<EOF | sudo config reload /dev/stdin -y
{
    "MGMT_INTERFACE": {
        "eth0|10.3.147.46/23": {
            "gwaddr": "10.3.146.1"
        }
    },
    "DEVICE_METADATA": {
        "localhost": {
            "hostname": "sonic",
            "subtype": "DualToR"
        }
    }
}
EOF

2. Config the switch MAC address with management port MAC address

sudo sonic-cfggen -H --write-to-db

3. View the configuration for L2 switch mode on stdout (optional)

Below is a sample command line. User should provide a SKU parameter. The output file is on stdout for validation purpose.

sudo sonic-cfggen --preset l2 -p -H -k Mellanox-SN2700-D48C8

If dual ToR configuration is required, add the argument -a '{"is_dualtor": true, "uplinks": [<uplink interfaces as list>], "downlinks": [<downlink interfaces as list>]}' as follows (any interfaces not specified as an uplink or downlink will be set to admin down):

sudo sonic-cfggen --preset l2 -p -H -k Mellanox-SN2700-D48C8 -a '{"is_dualtor": true, "uplinks": ["Ethernet24", "Ethernet28"], "downlinks": ["Ethernet0", "Ethernet4"]}'

Deprecated command for image 201811 (dual ToR configuration is not supported):

sonic-cfggen -t /usr/local/lib/python2.7/dist-packages/usr/share/sonic/templates/l2switch.j2 -p -k Mellanox-SN2700-D48C8

4. Load the configuration into ConfigDB

Below is a sample command line. User should provide a SKU parameter. Existing ConfigDB content not relating ports and VLAN will be kept.

sudo sonic-cfggen --preset l2 -p -H -k Mellanox-SN2700-D48C8 | sudo config load /dev/stdin -y

If dual ToR configuration is required, add the argument -a '{"is_dualtor": true, "uplinks": [<uplink interfaces as list>], "downlinks": [<downlink interfaces as list>]}' (any interfaces not specified as an uplink or downlink will be set to admin down):

sudo sonic-cfggen --preset l2 -p -H -k Mellanox-SN2700-D48C8 -a '{"is_dualtor": true, "uplinks": ["Ethernet24", "Ethernet28"], "downlinks": ["Ethernet0", "Ethernet4"]}' | sudo config load /dev/stdin -y

Deprecated command for image 201811 (dual ToR not supported):

sonic-cfggen -t /usr/local/lib/python2.7/dist-packages/usr/share/sonic/templates/l2switch.j2 -p -k Mellanox-SN2700-D48C8 | sudo config load /dev/stdin -y

5. Save ConfigDB for persistence

If dual ToR configuration has been applied, wait until show feature config mux show the State as enabled (this may take up to ~2 minutes):

admin@sonic:~$ show feature config mux
Feature    State    AutoRestart    Owner
---------  -------  -------------  -------
mux        enabled  enabled        local

Then save ConfigDB

sudo config save -y

6. Startup the system

If dual ToR configuration is required:

sudo config reload -y

Otherwise:

sudo systemctl restart swss

Port Speed Configuration CLI (optional)

Port speed is initially specified in the minigraph or generated in L2 switch mode and load into ConfigDB. During runtime, we could config port speed by CLI. Below is a sample.

sudo config interface speed Ethernet0 40000

We could verify the port speed by CLI.

show interface status

Sample command line output:

admin@sonic:~$ show interface status
  Interface            Lanes    Speed    MTU    Alias    Oper    Admin
-----------  ---------------  -------  -----  -------  ------  -------
  Ethernet0          0,1,2,3      40G   9100     etp1      up       up
  Ethernet4          4,5,6,7      40G   9100     etp2      up       up
  Ethernet8        8,9,10,11      40G   9100     etp3      up       up
 Ethernet12      12,13,14,15      40G   9100     etp4      up       up
 Ethernet16      16,17,18,19      40G   9100     etp5      up       up
 Ethernet20      20,21,22,23      40G   9100     etp6      up       up
 Ethernet24      24,25,26,27      40G   9100     etp7      up       up
 Ethernet28      28,29,30,31      40G   9100     etp8      up       up
 Ethernet32      32,33,34,35      40G   9100     etp9      up       up
 Ethernet36      36,37,38,39      40G   9100    etp10      up       up
 Ethernet40      40,41,42,43      40G   9100    etp11      up       up
 Ethernet44      44,45,46,47      40G   9100    etp12      up       up
 Ethernet48      48,49,50,51      40G   9100    etp13      up       up
 Ethernet52      52,53,54,55      40G   9100    etp14      up       up
 Ethernet56      56,57,58,59      40G   9100    etp15      up       up
 Ethernet60      60,61,62,63      40G   9100    etp16      up       up
 Ethernet64      64,65,66,67      40G   9100    etp17      up       up
 Ethernet68      68,69,70,71      40G   9100    etp18      up       up
 Ethernet72      72,73,74,75      40G   9100    etp19      up       up
 Ethernet76      76,77,78,79      40G   9100    etp20      up       up
 Ethernet80      80,81,82,83      40G   9100    etp21      up       up
 Ethernet84      84,85,86,87      40G   9100    etp22      up       up
 Ethernet88      88,89,90,91      40G   9100    etp23      up       up
 Ethernet92      92,93,94,95      40G   9100    etp24      up       up
 Ethernet96      96,97,98,99      40G   9100    etp25      up       up
Ethernet100  100,101,102,103      40G   9100    etp26      up       up
Ethernet104  104,105,106,107      40G   9100    etp27      up       up
Ethernet108  108,109,110,111      40G   9100    etp28      up       up
Ethernet112  112,113,114,115      40G   9100    etp29      up       up
Ethernet116  116,117,118,119      40G   9100    etp30      up       up
Ethernet120  120,121,122,123      40G   9100    etp31      up       up
Ethernet124  124,125,126,127      40G   9100    etp32      up       up

If you want to know the port number of one interface, normally you can find it in the 'Alias' column. For example the interface Ethernet0 has port number 1.

Dual ToR Mux Cable Configuration (optional)

By default, the active and standby ToRs for each port will be automatically determined at startup. To manually force a certain ToR to be active or standby for a specific port, use the command:

sudo config mux hwmode state <state> <port_name>

where

  • <state> can be either active or standby
  • <port_name> can be either all or any one interface name on the device connected to a mux cable.

References

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