This article provides information about the unicast-in-lpm knob and its support on QFX5K platforms running Junos.

The host table is skipped for unicast routes when the unicast-in-lpm knob is configured. All IPv4 unicast routes (Host and LPM) are directly installed in the LPM table. This feature is supported starting from release 21.2R1 on the QFX5K platforms running Junos. 

root@qfx5200> show configuration chassis
forwarding-options {
    lpm-profile {
        unicast-in-lpm;
    }
}

Before the 21.2R1 release, the unicast-in-lpm knob could be configured but had no effect. Adding or removing the knob would not restart the PFE, and host routes would still populate the host table first.

Starting from the 21.2R1 release, the unicast-in-lpm knob will take effect, causing the host table to be bypassed for all unicast routes. Adding or removing the knob will trigger a PFE restart to reallocate the forwarding table resources.

The "show chassis forwarding-options" command can be used to verify the active profile and the options enabled/disabled. 

Junos 21.1R1: 

root@qfx5200> > show chassis forwarding-options
localre:
--------------------------------------------------------------------------
UFT Configuration:
lpm-profile.
prefix-65-127 = enable
--------------Bank details for various types of entries------------------
Entry type                         Dedicated Bank Size(K)     Shared Bank Size(K)
L2(mac)                            8                          32 * num shared banks
L3(unicast & multicast)            8                          32 * num shared banks
Exact Match                        0                          16 * num shared banks
Longest Prefix Match(lpm)          16                         32 * num shared banks

root@qfx5200> show pfe route summary hw
Slot 0
Unit: 0
Profile active: lpm-profile
Type            Max       Used      Free      % free
----------------------------------------------------
IPv4 Host       8192      8184      0         0.00        <<<<<< host table fills up first
IPv4 LPM        131072    23        131049    99.98                     
IPv4 Mcast      4096      0         0         0.00
 
IPv6 Host       4096      4         0         0.00
IPv6 LPM(< 64)  16384     2         16382     99.99
IPv6 LPM(> 64)  16384     0         16382     99.99
IPv6 Mcast      2048      0         0         0.00


Junos 21.2R1:

root@qfx5200> show chassis forwarding-options
localre:
--------------------------------------------------------------------------
UFT Configuration:
lpm-profile.
prefix-65-127 = enable
unicast-in-lpm = enable
--------------Bank details for various types of entries------------------
Entry type                         Dedicated Bank Size(K)     Shared Bank Size(K)
L2(mac)                            8                          32 * num shared banks
L3(unicast & multicast)            8                          32 * num shared banks
Exact Match                        0                          16 * num shared banks
Longest Prefix Match(lpm)          16                         32 * num shared banks


root@qfx5200> show pfe route summary hw
Slot 0
Unit: 0
Profile active: lpm-profile
Type            Max       Used      Free      % free
----------------------------------------------------
IPv4 Host       8192      0         8192      100.00  <<<<< host table is skipped for unicast routes
IPv4 LPM        131072    45971     85101     64.93
IPv4 Mcast      4096      0         4096      100.00

IPv6 Host       4096      0         4096      100.00
IPv6 LPM(< 64)  16384     4         16380     99.98
IPv6 LPM(> 64)  16384     4         16380     99.98
IPv6 Mcast      2048      0         2048      100.00