What happen when TCAM max limit exceed ?

[ZAHIDHASEEB]

1- What happen if TCAM reaches to max limit ?

2- What is the meaning of unicast directly-connected routes ?

#show platform tcam utilization

CAM Utilization for ASIC# 0 Max Used
Masks/Values Masks/values

Unicast mac addresses: 6364/6364 575/575
IPv4 IGMP groups + multicast routes: 1120/1120 1/1
IPv4 unicast directly-connected routes: 6144/6144 6144/6144
IPv4 unicast indirectly-connected routes: 2048/2048 149/149
IPv4 policy based routing aces: 442/442 12/12
IPv4 qos aces: 512/512 21/21
IPv4 security aces: 954/954 35/35

Note: Allocation of TCAM entries per feature uses
a complex algorithm. The above information is meant
to provide an abstract view of the current TCAM utilization

[Giuseppe Larosa · Accepted solution]

Hello @ZAHIDHASEEB ,

in older platforms like a Catalyst 6500 when TCAM is full some entries are process switched as they cannot be stored in the CEF tables.

This could cause very high CPU usage.

Some modern platforms like Nexus 9500 simply drop traffic of entries that cannot be stored in TCAM tables in this way there is traffic loss but main cpu is protected from process switching user traffic flows.

About the second question unicast directly connected routes the name would lead to think of connected routes. Eventually hosts can count as one entry as there is the need to store their specific MAC address.

Hope to help

Giuseppe