01-05-2018 07:56 AM - edited 03-08-2019 01:18 PM
Dear All,
I would like to allocate some TCAM for arp-supression via this command:
hardware access-list tcam region arp-ether 256
I have read the TCAM Carving Guide, but it doesn't explain what impact turning off another TCAM region may have.
In my case, "ing-l2-span-filter" sounds like a reasonable feature to turn off but could anyone clarify what "ing-l2-span-filter" does?
switch# sho run all | in tcam hardware access-list tcam region ing-racl 1792 hardware access-list tcam region ing-l2-qos 256 hardware access-list tcam region ing-l3-vlan-qos 512 hardware access-list tcam region ing-sup 512 hardware access-list tcam region ing-l2-span-filter 256 hardware access-list tcam region ing-l3-span-filter 256 hardware access-list tcam region span 512 hardware access-list tcam region egr-racl 1792 hardware access-list tcam region egr-sup 256 [Everything else is 0]
The feature does not appear to be used:
switch# show hardware access-list resource utilization slot 1 ======= INSTANCE 0x0 ------------- ACL Hardware Resource Utilization (Mod 1) ---------------------------------------------------------- Used Free Percent Utilization ------------------------------------------------------------------- Ingress L2 SPAN ACL 0 256 0.00 Ingress L2 SPAN ACL IPv4 0 0.00 Ingress L2 SPAN ACL IPv6 0 0.00 Ingress L2 SPAN ACL MAC 0 0.00 Ingress L2 SPAN ACL ALL 0 0.00 Ingress L2 SPAN ACL OTHER 0 0.00 [...] Ingress L3/VLAN SPAN ACL 0 256 0.00 Ingress L3/VLAN SPAN ACL IPv4 0 0.00 Ingress L3/VLAN SPAN ACL IPv6 0 0.00 Ingress L3/VLAN SPAN ACL MAC 0 0.00 Ingress L3/VLAN SPAN ACL ALL 0 0.00 Ingress L3/VLAN SPAN ACL OTHER 0 0.00 [...] SPAN 0 512 0.00 SPAN IPv4 0 0.00 SPAN IPv6 0 0.00 SPAN MAC 0 0.00 SPAN ALL 0 0.00 SPAN OTHER 0 0.00 [...] INSTANCE 0x1 ------------- ACL Hardware Resource Utilization (Mod 1) ---------------------------------------------------------- Used Free Percent Utilization ------------------------------------------------------------------- Ingress L2 SPAN ACL 0 256 0.00 Ingress L2 SPAN ACL IPv4 0 0.00 Ingress L2 SPAN ACL IPv6 0 0.00 Ingress L2 SPAN ACL MAC 0 0.00 Ingress L2 SPAN ACL ALL 0 0.00 Ingress L2 SPAN ACL OTHER 0 0.00 [...] Ingress L3/VLAN SPAN ACL 0 256 0.00 Ingress L3/VLAN SPAN ACL IPv4 0 0.00 Ingress L3/VLAN SPAN ACL IPv6 0 0.00 Ingress L3/VLAN SPAN ACL MAC 0 0.00 Ingress L3/VLAN SPAN ACL ALL 0 0.00 Ingress L3/VLAN SPAN ACL OTHER 0 0.00 [...] SPAN 0 512 0.00 SPAN IPv4 0 0.00 SPAN IPv6 0 0.00 SPAN MAC 0 0.00 SPAN ALL 0 0.00 SPAN OTHER 0 0.00
I would rather know what I'm losing before I turn off a feature. Thanks for any guidance.
Solved! Go to Solution.
01-05-2018 08:36 AM
Good day,
The switch TCAM is, in simple words, a memory where a few set of instructions can be allocated. As an example, if I create an Acess List, the switch will use its TCAM to allocate this order, and when a packet comes in, the switch will look up in such memory to see if there is a special instruction for such packet.
Then, the TCAM memory is divided in parts, in order for features to install their respective set of instructions. When we ask the switch to carve the TCAM, it simply means that we want to distribute the memory space allocated to features differently.
In the following guide, one can see that removing space from "ing-l2-span-filter" may cause the switch to lose its ability to use filters when one configures a SPAN session, or when one uses the Packet Tracer feature.
ing-l2-span-filter: For filtering ingress
Layer 2 SPAN traffic (Cisco Nexus 9200
and 9300-EX Series switches only)
This may cause an issue if you would like to troubleshoot some other unrelated failure in the future, and a SPAN session is required. It would be advisable to browse the document above, and check which feature is used the least to make sure there are no undesired side effects.
Hope this helps.
Eduardo.
01-05-2018 08:36 AM
Good day,
The switch TCAM is, in simple words, a memory where a few set of instructions can be allocated. As an example, if I create an Acess List, the switch will use its TCAM to allocate this order, and when a packet comes in, the switch will look up in such memory to see if there is a special instruction for such packet.
Then, the TCAM memory is divided in parts, in order for features to install their respective set of instructions. When we ask the switch to carve the TCAM, it simply means that we want to distribute the memory space allocated to features differently.
In the following guide, one can see that removing space from "ing-l2-span-filter" may cause the switch to lose its ability to use filters when one configures a SPAN session, or when one uses the Packet Tracer feature.
ing-l2-span-filter: For filtering ingress
Layer 2 SPAN traffic (Cisco Nexus 9200
and 9300-EX Series switches only)
This may cause an issue if you would like to troubleshoot some other unrelated failure in the future, and a SPAN session is required. It would be advisable to browse the document above, and check which feature is used the least to make sure there are no undesired side effects.
Hope this helps.
Eduardo.
01-05-2018 10:14 AM
Thank you very much Eduardo, the guide provides a lot of answers.
This switch is a C93108TC-EX, and what I've noticed is that on trying to assign some TCAM to arp-ether (for EVPN ARP-suppression), I get:
switch(config)# hardware access-list tcam region arp-ether 256 ^ % Invalid command at '^' marker. switch(config)# sho run all | in "arp-ether" hardware access-list tcam region arp-ether 0
This is a bit weird, because I understood some of the earlier N9k switches needed this allocation.
01-05-2018 11:25 AM
Understood James,
I believe in newer platforms, if you are to configure BGP EVPN (or VXLAN) in the long run, it would be necessary to enable “system routing template-vxlan-scale” which in turn allocates the required TCAM space. Some documentation about it can be found here.
My two theories right now would be either the main feature allocates the TCAM space automatically, or we may need to remove first some TCAM feature and try to reserve space for arp-ether again.
Also, could you check if "show logging last 10" threw any error message?
Hope this helps.
Eduardo.
01-08-2018 09:41 AM
Hi Eduardo,
I've applied the "system routing template-vxlan-scale" and reloaded. Apparently this command is automated after 7.0(3)I5(1).
The ARP-Supression feature seems to enable with no errors:
interface nve1 description VXLAN VTEP source-interface loopback2 overlay-encapsulation vxlan host-reachability protocol bgp member vni 10328 suppress-arp ingress-replication protocol bgp [...] member vni 103967 associate-vrf exit
Still the arp-ether allocation shows up as zero:
switch# sho run all | in arp-ether hardware access-list tcam region arp-ether 0
This looks unusual, but I guess it's best if I test it so see whether the feature works.
01-08-2018 09:43 AM
Hi James,
That looks good, so far. Are you able to go under configuration mode and try to carve the TCAM for "arp-ether" now?
Otherwise, is there any way to test the feature to see if it allocates such space automatically?
Kind regards,
Eduardo.
01-08-2018 09:47 AM
Still the same result unfortunately:
switch(config)# hardware access-list tcam region arp-ether ^C chges-d-falsa-01(config)# hardware access-list tcam region arp-ether 256 ^ % Invalid command at '^' marker. switch(config)# hardware access-list tcam region ? egr-racl Egress RACL egr-sup Egress SUP ing-fstat Ingress FSTAT ing-ifacl Ingress PACL ing-l2-qos Ingress L2 QOS ing-l2-span-filter Ingress L2 SPAN filter ing-l3-span-filter Ingress L3 SPAN filter ing-l3-vlan-qos Ingress L3/VLAN QOS ing-racl Ingress RACL ing-rbacl Ingress RBACL ing-redirect Ingress Redirect ing-sup Ingress SUP nat Ingress NAT span SPAN vacl VACL
I'll be upgrading and testing these switches over the next few weeks, so will reply if the feature doesn't work.
01-22-2018 01:10 AM
Just to close down this thread, it appears that carving space for arp-ether is not required on the 9300-EX and FX series. You still have to do it on say the 9332PQ though:
conf ter
! Reduce RACL allocation: hardware access-list tcam region racl 512 copy run start
! Provide ARP-Ether: hardware access-list tcam region arp-ether 256 double-wide copy run start end
There is some documentation on this in the EVPN Config Example. by Lukas Krattiger.
07-20-2020 02:15 AM
it works with me :)
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: