Catalyst 9000 TCAM

[dervain.legbou-prestataire]

Hello dear Genius community members,

C9300 can function like a L3 device (as flat ip router or mpls PE). Per the datasheet it can handle at least 32.000 routes (24.000 direct routes + 8.000 indirect routes). Unfortunately when reaching around 7.000 routes (direct+indirect) we experience some forwarding issues related with logging messages like lake of resources. We did suspect TCAM overflow that has been confirmed by Cisco TAC. The only workaround is to make routes summarization in order to lower routing table. My thoughts is that indication from datasheet is a bit diffrent than the reality. Did someone face an issue like this?

[MHM Cisco World]

1-TCAM is HW and have specific size, BUT there is something called SDM template, 
where some costumer use template for MAC or unicast or net flow, 

2- One route not meaning it allocate one TCAM spaces, the algorithm is complex as cisco mention in below statement.

Switch# show platform tcam utilization

CAM Utilization for ASIC# 0 Max Used

Masks/Values Masks/values

Unicast mac addresses: 6364/6364 31/31

IPv4 IGMP groups + multicast routes: 1120/1120 1/1

IPv4 unicast directly-connected routes: 6144/6144 4/4

IPv4 unicast indirectly-connected routes: 2048/2048 2047/2047

IPv4 policy based routing aces: 452/452 12/12

IPv4 qos aces: 512/512 21/21

IPv4 security aces: 964/964 30/30

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

In the example, the IP indirectly-connected routes resource is full even though the output shows only 2047 of 2048 maximum as in use.

[dervain.legbou-prestataire]

Thanks for your quick feedback.

We already tried SDM option but Only 2 template are available: Access and NAT.

The walue are almost the same apart QOS and PBR row. 

If we could get the cli to decrease MAC's room and increase Unicast'one.

As i understood it is a hardware limitations. No way to give more room even if we purchase a license.

[MHM Cisco World]

Yes it hardware limitations and license do not give more room.

[marce1000]

 - You may look at this command (if available)  hardware access-list tcam region ?   , look at the available options.

 M.

[dervain.legbou-prestataire]

Hello marce1000,  But it seems that the command is related to Nexus hardware. My limitation is on catalyst 9300.

By the way thanks for all.

[marce1000]

                              - FYI : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvg60292

 You may also find this document useful : https://www.cisco.com/c/en/us/support/docs/switches/catalyst-9500-series-switches/217703-understand-hardware-resources-on-catalys.html

 M.

[MHM Cisco World]

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/troubleshooting/cpu_util.html

check this doc. at it end some detail bout TCAM utilize.

[dervain.legbou-prestataire · Accepted solution]

Hello,

Thanks to all of you for the links provided. I have already seen all of them when i was troubleshooting my issues and how to overcome it. As i said before, things are like all information going to hardware limitations like Cisco told us. The oak of solution is to lower down vpnv4 prefixes by aggregate them. I have already tested on one PE and the TCAM went lower than before.