Unknown Protocol Drops incremented frequently on router's FastEthernet Interfaces

[vc.gundapaneni]

Hi,

Very recently, we had up graded our Leased Line's B/W from Serial 2Mbps to FastEthernet 4Mbps. Router A is Cisco 3845 and Router B is Cisco 1841.

We had changed the HWIC's cards also to HWIC-2FE on both ends as per our requirement.IOS also upgraded.

Here, we observed frequently incremented unknown protocol drops on Router B's FastEthernet Interfaces (Both on  WAN & LAN ports).

And RTO's also generated.With this we are unable access our LAN's vice versa. What is the best resolution for this? Please find out the below ping statistics and do the needful.

Pinging 10.1.1.20 with 32 bytes of data:

Reply from 10.1.1.20: bytes=32 time=268ms TTL=124

Reply from 10.1.1.20: bytes=32 time=232ms TTL=124

Request timed out.

Reply from 10.1.1.20: bytes=32 time=231ms TTL=124

Reply from 10.1.1.20: bytes=32 time=91ms TTL=124

Reply from 10.1.1.20: bytes=32 time=226ms TTL=124

Reply from 10.1.1.20: bytes=32 time=230ms TTL=124

Reply from 10.1.1.20: bytes=32 time=232ms TTL=124

Request timed out.

Reply from 10.1.1.20: bytes=32 time=209ms TTL=124

Reply from 10.1.1.20: bytes=32 time=219ms TTL=124

Reply from 10.1.1.20: bytes=32 time=251ms TTL=124

Reply from 10.1.1.20: bytes=32 time=174ms TTL=124

Reply from 10.1.1.20: bytes=32 time=223ms TTL=124

Reply from 10.1.1.20: bytes=32 time=218ms TTL=124

Reply from 10.1.1.20: bytes=32 time=221ms TTL=124

Reply from 10.1.1.20: bytes=32 time=179ms TTL=124

Reply from 10.1.1.20: bytes=32 time=240ms TTL=124

Reply from 10.1.1.20: bytes=32 time=193ms TTL=124

Reply from 10.1.1.20: bytes=32 time=240ms TTL=124

Reply from 10.1.1.20: bytes=32 time=191ms TTL=124

Reply from 10.1.1.20: bytes=32 time=191ms TTL=124

Reply from 10.1.1.20: bytes=32 time=203ms TTL=124

Reply from 10.1.1.20: bytes=32 time=209ms TTL=124

Reply from 10.1.1.20: bytes=32 time=236ms TTL=124

Reply from 10.1.1.20: bytes=32 time=128ms TTL=124

Reply from 10.1.1.20: bytes=32 time=234ms TTL=124

Reply from 10.1.1.20: bytes=32 time=268ms TTL=124

Reply from 10.1.1.20: bytes=32 time=212ms TTL=124

Reply from 10.1.1.20: bytes=32 time=144ms TTL=124

Request timed out.

Request timed out.

Reply from 10.1.1.20: bytes=32 time=198ms TTL=124

Reply from 10.1.1.20: bytes=32 time=302ms TTL=124

Reply from 10.1.1.20: bytes=32 time=245ms TTL=124

Reply from 10.1.1.20: bytes=32 time=306ms TTL=124

Reply from 10.1.1.20: bytes=32 time=249ms TTL=124

Reply from 10.1.1.20: bytes=32 time=185ms TTL=124

Reply from 10.1.1.20: bytes=32 time=168ms TTL=124

Reply from 10.1.1.20: bytes=32 time=220ms TTL=124

Reply from 10.1.1.20: bytes=32 time=181ms TTL=124

Reply from 10.1.1.20: bytes=32 time=311ms TTL=124

Reply from 10.1.1.20: bytes=32 time=267ms TTL=124

Reply from 10.1.1.20: bytes=32 time=234ms TTL=124

Reply from 10.1.1.20: bytes=32 time=208ms TTL=124

Reply from 10.1.1.20: bytes=32 time=258ms TTL=124

Reply from 10.1.1.20: bytes=32 time=262ms TTL=124

Reply from 10.1.1.20: bytes=32 time=172ms TTL=124

Reply from 10.1.1.20: bytes=32 time=253ms TTL=124

Reply from 10.1.1.20: bytes=32 time=227ms TTL=124

Reply from 10.1.1.20: bytes=32 time=199ms TTL=124

Reply from 10.1.1.20: bytes=32 time=336ms TTL=124

Reply from 10.1.1.20: bytes=32 time=205ms TTL=124

Reply from 10.1.1.20: bytes=32 time=250ms TTL=124

Reply from 10.1.1.20: bytes=32 time=345ms TTL=124

Reply from 10.1.1.20: bytes=32 time=199ms TTL=124

Reply from 10.1.1.20: bytes=32 time=197ms TTL=124

Reply from 10.1.1.20: bytes=32 time=205ms TTL=124

Reply from 10.1.1.20: bytes=32 time=194ms TTL=124

Reply from 10.1.1.20: bytes=32 time=190ms TTL=124

Reply from 10.1.1.20: bytes=32 time=230ms TTL=124

Reply from 10.1.1.20: bytes=32 time=195ms TTL=124

Reply from 10.1.1.20: bytes=32 time=223ms TTL=124

Reply from 10.1.1.20: bytes=32 time=258ms TTL=124

Reply from 10.1.1.20: bytes=32 time=204ms TTL=124

Reply from 10.1.1.20: bytes=32 time=268ms TTL=124

Reply from 10.1.1.20: bytes=32 time=271ms TTL=124

Reply from 10.1.1.20: bytes=32 time=215ms TTL=124

Reply from 10.1.1.20: bytes=32 time=178ms TTL=124

Reply from 10.1.1.20: bytes=32 time=244ms TTL=124

Reply from 10.1.1.20: bytes=32 time=229ms TTL=124

Reply from 10.1.1.20: bytes=32 time=242ms TTL=124

Reply from 10.1.1.20: bytes=32 time=278ms TTL=124

Reply from 10.1.1.20: bytes=32 time=294ms TTL=124

Reply from 10.1.1.20: bytes=32 time=214ms TTL=124

Reply from 10.1.1.20: bytes=32 time=217ms TTL=124

Reply from 10.1.1.20: bytes=32 time=363ms TTL=124

Reply from 10.1.1.20: bytes=32 time=252ms TTL=124

Reply from 10.1.1.20: bytes=32 time=254ms TTL=124

Reply from 10.1.1.20: bytes=32 time=256ms TTL=124

Reply from 10.1.1.20: bytes=32 time=268ms TTL=124

Reply from 10.1.1.20: bytes=32 time=229ms TTL=124

Reply from 10.1.1.20: bytes=32 time=161ms TTL=124

Reply from 10.1.1.20: bytes=32 time=166ms TTL=124

Reply from 10.1.1.20: bytes=32 time=234ms TTL=124

Request timed out.

Request timed out.

Reply from 10.1.1.20: bytes=32 time=218ms TTL=124

Reply from 10.1.1.20: bytes=32 time=200ms TTL=124

Reply from 10.1.1.20: bytes=32 time=210ms TTL=124

Reply from 10.1.1.20: bytes=32 time=217ms TTL=124

Reply from 10.1.1.20: bytes=32 time=245ms TTL=124

Reply from 10.1.1.20: bytes=32 time=206ms TTL=124

Reply from 10.1.1.20: bytes=32 time=209ms TTL=124

Reply from 10.1.1.20: bytes=32 time=317ms TTL=124

Reply from 10.1.1.20: bytes=32 time=164ms TTL=124

Reply from 10.1.1.20: bytes=32 time=213ms TTL=124

Reply from 10.1.1.20: bytes=32 time=289ms TTL=124

Reply from 10.1.1.20: bytes=32 time=181ms TTL=124

Reply from 10.1.1.20: bytes=32 time=231ms TTL=124

Reply from 10.1.1.20: bytes=32 time=183ms TTL=124

Reply from 10.1.1.20: bytes=32 time=363ms TTL=124

Reply from 10.1.1.20: bytes=32 time=284ms TTL=124

Reply from 10.1.1.20: bytes=32 time=279ms TTL=124

Reply from 10.1.1.20: bytes=32 time=285ms TTL=124

Request timed out.

Reply from 10.1.1.20: bytes=32 time=167ms TTL=124

Reply from 10.1.1.20: bytes=32 time=182ms TTL=124

Reply from 10.1.1.20: bytes=32 time=190ms TTL=124

Reply from 10.1.1.20: bytes=32 time=316ms TTL=124

Reply from 10.1.1.20: bytes=32 time=196ms TTL=124

Reply from 10.1.1.20: bytes=32 time=130ms TTL=124

Reply from 10.1.1.20: bytes=32 time=212ms TTL=124

Reply from 10.1.1.20: bytes=32 time=152ms TTL=124

Reply from 10.1.1.20: bytes=32 time=208ms TTL=124

Reply from 10.1.1.20: bytes=32 time=92ms TTL=124

Reply from 10.1.1.20: bytes=32 time=177ms TTL=124

Reply from 10.1.1.20: bytes=32 time=211ms TTL=124

Reply from 10.1.1.20: bytes=32 time=196ms TTL=124

Reply from 10.1.1.20: bytes=32 time=281ms TTL=124

Reply from 10.1.1.20: bytes=32 time=347ms TTL=124

Reply from 10.1.1.20: bytes=32 time=248ms TTL=124

Reply from 10.1.1.20: bytes=32 time=193ms TTL=124

Reply from 10.1.1.20: bytes=32 time=182ms TTL=124

Reply from 10.1.1.20: bytes=32 time=219ms TTL=124

Reply from 10.1.1.20: bytes=32 time=253ms TTL=124

Reply from 10.1.1.20: bytes=32 time=210ms TTL=124

Reply from 10.1.1.20: bytes=32 time=138ms TTL=124

Reply from 10.1.1.20: bytes=32 time=232ms TTL=124

Reply from 10.1.1.20: bytes=32 time=177ms TTL=124

Reply from 10.1.1.20: bytes=32 time=325ms TTL=124

Reply from 10.1.1.20: bytes=32 time=242ms TTL=124

Reply from 10.1.1.20: bytes=32 time=170ms TTL=124

Reply from 10.1.1.20: bytes=32 time=184ms TTL=124

Reply from 10.1.1.20: bytes=32 time=164ms TTL=124

Reply from 10.1.1.20: bytes=32 time=196ms TTL=124

Request timed out.

Reply from 10.1.1.20: bytes=32 time=292ms TTL=124

Reply from 10.1.1.20: bytes=32 time=207ms TTL=124

Reply from 10.1.1.20: bytes=32 time=266ms TTL=124

Reply from 10.1.1.20: bytes=32 time=253ms TTL=124

Reply from 10.1.1.20: bytes=32 time=243ms TTL=124

Reply from 10.1.1.20: bytes=32 time=218ms TTL=124

Reply from 10.1.1.20: bytes=32 time=221ms TTL=124

Reply from 10.1.1.20: bytes=32 time=296ms TTL=124

Reply from 10.1.1.20: bytes=32 time=278ms TTL=124

Reply from 10.1.1.20: bytes=32 time=230ms TTL=124

Reply from 10.1.1.20: bytes=32 time=294ms TTL=124

Reply from 10.1.1.20: bytes=32 time=235ms TTL=124

Reply from 10.1.1.20: bytes=32 time=233ms TTL=124

Reply from 10.1.1.20: bytes=32 time=210ms TTL=124

Reply from 10.1.1.20: bytes=32 time=222ms TTL=124

Reply from 10.1.1.20: bytes=32 time=293ms TTL=124

Reply from 10.1.1.20: bytes=32 time=228ms TTL=124

Reply from 10.1.1.20: bytes=32 time=206ms TTL=124

Reply from 10.1.1.20: bytes=32 time=205ms TTL=124

Reply from 10.1.1.20: bytes=32 time=229ms TTL=124

Reply from 10.1.1.20: bytes=32 time=135ms TTL=124

Reply from 10.1.1.20: bytes=32 time=229ms TTL=124

Reply from 10.1.1.20: bytes=32 time=213ms TTL=124

Reply from 10.1.1.20: bytes=32 time=188ms TTL=124

Reply from 10.1.1.20: bytes=32 time=294ms TTL=124

Reply from 10.1.1.20: bytes=32 time=245ms TTL=124

Ping statistics for 10.1.1.20:

    Packets: Sent = 163, Received = 155, Lost = 8 (4% loss),

Approximate round trip times in milli-seconds:

    Minimum = 91ms, Maximum = 363ms, Average = 226ms

Thanks

VC Gundapaneni

[Joseph W. Doherty]

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Posting

Did you reduce the shaper's CIR rate?  If so, did the ping tests stop dropping packets and average ping time improve?

If you're  now seeing drops on the interfaces, that's to be expected. Some or all  flows are attempting to use more bandwidth than what's available.  All  TCP stacks (within other limits) will "probe" available bandwidth by  trying to use more and more bandwidth until they see an adverse impact  to their flow (such as a packet drop or drops).

So, drops are often normal part of flow bandwidth.  The only other methods to reduce them would be to, for TCP, shape returning ACKs and/or adjust receiver's RWIN.  (Something that's often done by special bandwidth management appliances.)   Otherwise, you need to increase bandwidth.  However, as long as  transactional traffic is getting the service levels required and bulk  traffic is transferring data within required time windows, you only need  to accept the fact that some packet drops are normal.

PS:

Forgot to add, the FQ portion of the provided policy should, more or less, only drop packets from the flows trying to use too much bandwidth.