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i have a n3k-3064pq-10gx and i want to have 1x pbr to change some 400x SVI next-hop , when i tried to apply the pbr to a l3 interface or SVI it says "% Could not apply PBR route-map - Specified TCAM region size is zero' so from https://community.cisco.com/t5/switching/nexus-3k-tcam-carving-region-cannot-be-configured/td-p/3405266 i found that i should reduce racl and increase pbr in tcam so my questions are :

  1. i have reduce racl from 512 to 256 and increase pbr from 0 to 256 , so what does these values mean? this mean i can create 256x PBR  ? or this mean i can assign 1x PBR to 256x SVI or layer 3?

  2. when i reduce racl from 512 to 256 it does not cause any problem for my router and can you explain a bit on this?

thanks,

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    – Ron Maupin ♦
    Commented Dec 16, 2020 at 23:32

2 Answers 2

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By default entire TCAM is occupied and you need to release some resources (not necessarily the racl) in order to increase others.

In general, different resources might occupy different TCAM space per single entity. And some resources cannot be released. Allocations can be done in strictly specified chunks. You can see currently allocated regions by:

show hardware profile tcam region

and verify actual usage by:

show hardware access-list resource utilization

(or show hardware capacity forwarding). For example, this is my config for ARP ALCs:

hardware profile tcam region racl 256 
hardware profile tcam region e-racl 256 
hardware profile tcam region arpacl 256
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You're on the right track -- you're creating PBR entries in the TCAM and using those entries (maybe just one) for many interfaces. In most cases, ACL-like structures are able to be re-used by any number of interfaces. That's why it's okay that the switch only has room for a few hundred entries system-wide.

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  • So as i understand that mean i can create 256x pbr, but i can create 1x PBR and assign to many SVIs or routed interface, for example i can create 1x pbr and set nexthop to 1.2.3.4 and assign it to 400x SVIs but it will calculate it as 1x PBR in tcam and it does not count SVIs in tcam ? and it does not cause any problem for the switch , am i right?
    – Blackmetal
    Commented Oct 4, 2020 at 5:52

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