High Output Drops on 6500

[smitesh kharecha]

Hi

Have got 2 6500 in VSS. I'm seeing unsual high output drops.

IOS Version: advipservicesk9-mz.151-1.SY.bin

Seeing too much output drops on interface ( in millions). When checked buffers ( output pasted below), it also shows enourmous drops.

Not too sure, but is this normal or is there something fishy; which needs to be investigated.

Any help will be highly appriciated.

Counters cleared 1 week 4 days ago:

This router has dropped 100875 packet(s) (0.01557%) due to a shortage

of 'Small buffers'.

WARNING: This router has dropped 22852 packet(s) (0.16384%) due to a shortage of

'Medium buffers'.

WARNING: This router has dropped 5737 packet(s) (0.0635%) due to a shortage of 'Middle

Buffer elements:

    499 in free list (500 max allowed)

    928676239 hits, 0 misses, 0 created

Public buffer pools:

Small buffers, 104 bytes (total 1024, permanent 1024, peak 20636 @ 1w1d):

    1004 in free list (128 min, 2048 max allowed)

    647686487 hits, 202592

misses, 54099 trims, 54099 created

    100875 failures (0 no memory)

Medium buffers, 256 bytes (total 3000, permanent 3000, peak 6061 @ 1w1d):

    2994 in free list (64 min, 3000 max allowed)

    13908659 hits, 32324 misses, 3300 trims, 3300 created

22852 failures (0 no memory)

Middle buffers, 600 bytes (total 512, permanent 512, peak 3199 @ 1w1d):

    507 in free list (64 min, 1024 max allowed)

    9020841 hits, 8259 misses, 2752 trims, 2752 created

    5737 failures (0 no memory)

Big buffers, 1536 bytes (total 1000, permanent 1000, peak 3129 @ 1w1d):

    1000 in free list (64 min, 1000 max allowed)

    20657323 hits, 2983 misses, 2134 trims, 2134 created

    885 failures (0 no memory)

VeryBig buffers, 4520 bytes (total 10, permanent 10, peak 102 @ 1w1d):

    9 in free list (0 min, 100 max allowed)

    1581823 hits, 724 misses, 104 trims, 104 created

    688 failures (0 no memory)

Regards,

Smitesh Kharecha

[Reza Sharifi]

Hi,

Do you have any mismatch speed between the interfaces that comes into the switch and goes out (Gig vs 10Gig)?

Sometimes, this happens when you go from one speed to another

Any interface MTU mismatch configured?

[smitesh kharecha]

Hi,

Nope no speed or mtu mismatches.

Regards,

Smitesh

[Rahul Kukreja]

Failures in small/medium buffer are not indicative of packet drops
Only the failure counter in Huge Buffers is indicative of packet drops.

You may refer the following URL -
http://www.cisco.com/en/US/products/hw/modules/ps2643/products_tech_note09186a0080093fc5.shtml#topic1

Also looking at the sh buffer o/p here are few observations -

- number of hits in small buffer, looks like the number of packets with size < 104 bytes are much higher than other - which will vary based on the traffic on the device.

- The difference between total and free list is very less - so there is no buffer leak

- There was some activity 1 week 1 day ago and during that time all the buffers reached at their peak (i.e. the traffic at that time was high), you get more information by using the command show buffers usage at that time.

- HTH

Rahul