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[SRX] Understanding 'swfabx' interface on High-End SRX devices

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Article ID: KB35953 KB Last Updated: 19 Jun 2020Version: 1.0
Summary:

Ethernet ports support various Layer 2 features such as spanning-tree protocols (STPs), IEEE 802.1x, Link Layer Discovery Protocol (LLDP), and Multiple VLAN Registration Protocol (MVRP). With the extension of Layer 2 switching capability to devices in a chassis cluster, you can use Ethernet switching features on both nodes of a chassis cluster.

To ensure that Layer 2 switching works seamlessly across chassis cluster nodes, a dedicated physical link connecting the nodes is required. This type of link is called a switching fabric interface( swfab). Its purpose is to carry Layer 2 traffic between nodes.

This article explains the occurrence of CLI error 'error: device swfabx not found' in SRX High-End series devices and unsupported L2-learning in High-End SRX series devices.
Symptoms:

Warning Message:

user@host> show configuration protocols
l2-learning {
##
## Warning: statement ignored: unsupported platform (srx4600) <--
Warning Message on SRX4600 device.
##
global-mode switching;

Solution:

Interfaces 'swfab0' and 'swfab1' are used to enable switching in the SRX chassis cluster. These interfaces 'swfab0' and 'swfab1' fail to function properly in High-End SRX devices because Layer 2 switching capability feature is not supported on SRX High-End Series.

This can be verified by the warning that gets displayed when checking the configuration of protocols under L2-learning (there may be a significant delay noticed in the output display):

....
user@host> show configuration protocols
l2-learning {
##
## Warning: statement ignored: unsupported platform (srx4600)
##
global-mode switching;

Initially, when no configuration is present on swfab interface, the output seems normal. Check below:

user@host> show interfaces swfab0    
Aug 09 13:45:32
Physical interface: swfab0, Enabled, Physical link is Down
  Interface index: 129, SNMP ifIndex: 533
  Link-level type: Ethernet, MTU: 9014, Speed: Unspecified, BPDU Error: None,
  Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
  Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1,
  Minimum bandwidth needed: 0
  Device flags   : Present Running
  Interface flags: Hardware-Down SNMP-Traps Internal: 0x4000
  Current address: 58:00:bb:89:af:2c, Hardware address: 58:00:bb:89:af:2c
  Last flapped   : 2018-08-07 15:02:40 UTC (1d 22:43 ago)
    Input packets : 0
    Output packets: 0

user@host> show interfaces swfab1   
Aug 09 13:45:32
Physical interface: swfab1, Enabled, Physical link is Down
  Interface index: 129, SNMP ifIndex: 533
  Link-level type: Ethernet, MTU: 9014, Speed: Unspecified, BPDU Error: None,
  Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
  Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1,
  Minimum bandwidth needed: 0
  Device flags   : Present Running
  Interface flags: Hardware-Down SNMP-Traps Internal: 0x4000
  Current address: 58:00:bb:89:af:2c, Hardware address: 58:00:bb:89:af:2c
  Last flapped   : 2018-08-07 15:02:40 UTC (1d 22:43 ago)
    Input packets : 0
    Output packets: 0

When we try to enable a basic configuration and check the same interface output, we can see an error:

Example:

user@host# show | compare
[edit interfaces]
+   swfab0 {
+       fabric-options {
+           member-interfaces {   <-- Added simple configuration
+               xe-1/1/6;  
+               xe-1/1/7;
+           }
+       }
+   }
+   swfab1 {
+       fabric-options {
+           member-interfaces {   <-- Added simple configuration
+               xe-8/1/6;
+               xe-8/1/7;
+           }
+       }
+   }

{primary:node1}
user@host> show interfaces swfab0
Physical interface: swfab0, Enabled, Physical link is Up
Interface index: 131, SNMP ifIndex: 539
Link-level type: Ethernet, MTU: 9014, Speed: 20Gbps, BPDU Error: None,
Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1,
Minimum bandwidth needed: 0
Device flags   : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Current address: 58:00:bb:89:af:2c, Hardware address: 58:00:bb:89:af:2c
Last flapped   : 2018-07-09 07:52:56 UTC (00:03:16 ago)
Input rate     : 0 bps (0 pps)
Output rate    : 0 bps (0 pps)
error: remote statistics get for interface swfab1.0 failed: Resource temporarily unavailable (35)

{primary:node1}
user@host> show interfaces swfab1
Physical interface: swfab1, Enabled, Physical link is Up
Interface index: 131, SNMP ifIndex: 539
Link-level type: Ethernet, MTU: 9014, Speed: 20Gbps, BPDU Error: None,
Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1,
Minimum bandwidth needed: 0
Device flags   : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Current address: 58:00:bb:89:af:2c, Hardware address: 58:00:bb:89:af:2c
Last flapped   : 2018-07-09 07:52:56 UTC (00:03:16 ago)
Input rate     : 0 bps (0 pps)
Output rate    : 0 bps (0 pps)
error: remote statistics get for interface swfab1.0 failed: Resource temporarily unavailable (35)

The interface terse option shows that the interfaces are up and running:

user@host> show interfaces terse | match swfab*
xe-1/1/6.0              up    up   aenet    --> swfab0.0
xe-1/1/7.0              up    up   aenet    --> swfab0.0
xe-8/1/6.0              up    up   aenet    --> swfab1.0
xe-8/1/7.0              up    up   aenet    --> swfab1.0
swfab0                  up    up
swfab0.0                up    up
swfab1                  up    up
swfab1.0                up    up

The Ethernet switching interfaces output seems to be fine:

user@host> show ethernet-switching interfaces
swfab0:

Name               Status
xe-1/1/6           up
xe-1/1/7           up
swfab1:

Name               Status
xe-8/1/6           up
xe-8/1/7           up

The interface output for individual swfab returns an error:

{primary:node0}[edit]
root@node0_anderson1# run show interfaces swfab0
error: device swfab0 not found

{primary:node0}[edit]
root@node0_anderson1# run show interfaces swfab1   
error: device swfab1 not found


This is an expected behavior since L2 Ethernet switching is not supported by SRX HE Series devices.

Note: It is also expected when the outputs for the above-listed commands take more than 10-20 seconds to display. Since these are unsupported features, such anomalies can be normal.

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