01-13-2015 11:00 PM - edited 03-07-2019 10:12 PM
Hello everyone!
I have noticed on my 3750 stack these things:
sh platform tcam utilization
CAM Utilization for ASIC# 0 Max Used
Masks/Values Masks/values
Unicast mac addresses: 528/4224 508/3998
IPv4 IGMP groups + multicast routes: 144/1152 11/47
IPv4 unicast directly-connected routes: 528/4224 508/3998
IPv4 unicast indirectly-connected routes: 272/2176 64/451
IPv4 policy based routing aces: 512/512 2/2
IPv4 qos aces: 528/528 82/82
IPv4 security aces: 1024/2048 27/27
# of HL3U fibs 2229
# of HL3U adjs 1831
# of HL3U mpaths 2
# of HL3U covering-fibs 1
# of HL3U fibs with adj failures 4
Fibs of Prefix length 0, with TCAM fails: 0
Fibs of Prefix length 1, with TCAM fails: 0
Fibs of Prefix length 2, with TCAM fails: 0
Fibs of Prefix length 3, with TCAM fails: 0
Fibs of Prefix length 4, with TCAM fails: 0
Fibs of Prefix length 5, with TCAM fails: 0
Fibs of Prefix length 6, with TCAM fails: 0
Fibs of Prefix length 7, with TCAM fails: 0
Fibs of Prefix length 8, with TCAM fails: 0
Fibs of Prefix length 9, with TCAM fails: 0
Fibs of Prefix length 10, with TCAM fails: 0
Fibs of Prefix length 11, with TCAM fails: 0
Fibs of Prefix length 12, with TCAM fails: 0
Fibs of Prefix length 13, with TCAM fails: 0
Fibs of Prefix length 14, with TCAM fails: 0
Fibs of Prefix length 15, with TCAM fails: 0
Fibs of Prefix length 16, with TCAM fails: 0
Fibs of Prefix length 17, with TCAM fails: 0
Fibs of Prefix length 18, with TCAM fails: 0
Fibs of Prefix length 19, with TCAM fails: 0
Fibs of Prefix length 20, with TCAM fails: 0
Fibs of Prefix length 21, with TCAM fails: 0
Fibs of Prefix length 22, with TCAM fails: 0
Fibs of Prefix length 23, with TCAM fails: 0
Fibs of Prefix length 24, with TCAM fails: 0
Fibs of Prefix length 25, with TCAM fails: 0
Fibs of Prefix length 26, with TCAM fails: 0
Fibs of Prefix length 27, with TCAM fails: 0
Fibs of Prefix length 28, with TCAM fails: 0
Fibs of Prefix length 29, with TCAM fails: 0
Fibs of Prefix length 30, with TCAM fails: 0
Fibs of Prefix length 31, with TCAM fails: 0
Fibs of Prefix length 32, with TCAM fails: 107973
Fibs of Prefix length 33, with TCAM fails: 0
As far as I understand, MAC address table is full, but what does this mean?
Pv4 unicast directly-connected routes: 528/4224 508/3998
Do I have a lot of connected routes? I dont have more than 20 connected routes
sh ip arp summary gives this:
1925 IP ARP entries, with 50 of them incomplete
What should I do to optimize it?
Thank you!
Solved! Go to Solution.
01-15-2015 02:53 AM
Yes, for efficient routing the directly connected hosts must have a FIB entry.
cheers,
Seb.
01-15-2015 01:35 AM
Hi there,
What SDM template are you running?
sh sdm prefer
Do you handle any IPv6 traffic on this switch?
Do you run VTP on this switch? If not, are there VLANs trunked to it that carry a lot of L2 traffic but are not used on any switchports other than the uplink? If so, your mac address table will get filled with entries created by broadcasts.
What is this switches function, edge, distribution, core? If it is used as a core switch can you push some of the SVIs out towards edge and have purely L3 links between edge and core?
cheers,
Seb.
01-15-2015 01:40 AM
Hello Seb, thank you for your answer
SDM is
sh sdm prefer
The current template is "desktop access IPv4" template.
The selected template optimizes the resources in
the switch to support this level of features for
8 routed interfaces and 1024 VLANs.
number of unicast mac addresses: 4K
number of IPv4 IGMP groups + multicast routes: 1K
number of IPv4 unicast routes: 6K
number of directly-connected IPv4 hosts: 4K
number of indirect IPv4 routes: 2K
number of IPv4 policy based routing aces: 0.5K
number of IPv4/MAC qos aces: 0.5K
number of IPv4/MAC security aces: 2K
No, IPv6 traffic, no VTP. And yes, there are VLANs trunked but not used on edge ports since this is our Bridge in MST
The switch is edge/distribution.
Is it an SVI problem? Do I have to minimize them?
01-15-2015 02:00 AM
According to:
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swsdm.html
...you will gain another 2k mac addresses by running:
!
sdm prefer default
!
This would require a reload of the switch.
The SVIs are only a problem if they are seeing a lot of MAC addresses, moving the routing of these towards your edge may free up some space.
For each routed VLAN, what is the output of:
sh mac address-table dynamic vlan <xx>
cheers,
Seb
01-15-2015 02:06 AM
Thank you,
I know I can switch to Default but it requires restart of the switch stack which is the last option
I was wondering what can cause this
iPv4 unicast directly-connected routes: 528/4224 508/3998
and this:
Fibs of Prefix length 32, with TCAM fails: 107973
Is it MAC addresses or something else?
01-15-2015 02:24 AM
Each host (/32) will occupy a FIB entry, these are the 'directly-connected routes'.
The TCAM fails for /32 indicate that the switch is unable to create a new FIB entry when it sees a new L3 address so packets must be punted to the CPU in order to route them (this will cause increase CPU ultilization).
Clearly for the subnets you are routing on the 3750 you are exceeding the maximum number hosts it can store in its FIB and efficiently route. You need to move (some of) your SVIs.
01-15-2015 02:36 AM
Thank you Seb,
So just to make it clear each host address must be included in FIB right?
So directly connected routes are not only those I create with SVI, but also all the hosts IP addresses for these SVIs, right?
01-15-2015 02:53 AM
Yes, for efficient routing the directly connected hosts must have a FIB entry.
cheers,
Seb.
01-15-2015 10:42 PM
Dear Seb,
I have removed around 300 IP hosts from the switch. I used to have around 2100 ARP entries, no I have 1800
But it still shows
Fibs of Prefix length 32, with TCAM fails: 108689
And this number did not change
IPv4 unicast directly-connected routes: 528/4224 508/3996
Am I doing something wrong?
01-16-2015 01:50 AM
Morning,
From the DHCP leases you offer on the remaing connected VLANs which you are still routing on the switch do you know if the maximum concurrent leases exceeds 528?
The TCAM fails will still increment. I don't think you can clear the counter without a switch reload. With the changes you have made so far I am sure the number will be climbing slower.
cheers,
Seb.
01-16-2015 02:26 AM
Hello Seb,
Yes, it is more than 528
The TCAM fails number fluctuates, from more to less, but it is always around 108765
Do I still have to minimize my connected routes? When removed around 300 IP hosts from the switch, TCAM fails number did not change dramatically, sometime it is even more
01-16-2015 03:32 AM
How many DHCP leases are in use on these VLANs?
I struggle to belive the TCAM fails is not a counter, I would expect it to always climb.
You really need to consider chaging the SDM template. Can you schedule an outage for the weekend?
01-16-2015 03:38 AM
DHCP leases is around 1300.
It is too late for a schedule on this weekend, I will have to postpone it till next week
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