CUCM Packet Loss from Switch

[Vaijanath Sonvane]

Dear Support,

I just noticed one thing about CUCM that when I ping(extended) CUCM 6.x or 7.x form PC there is no packet loss but when I ping the same CUCM from cisco switch on which these servers are connected there is a specific packet drop pattern:

CUCM 6.x

CiscoSwitch02#ping
Protocol [ip]: 10.132.5.25
Target IP address: 10.132.5.25
Repeat count [5]: 50
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 50, 100-byte ICMP Echos to 10.132.5.25, timeout is 2 seconds:
!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!
Success rate is 84 percent (42/50), round-trip min/avg/max = 1/1/1 ms
CiscoSwitch02#

CUCM 7.x

CiscoSwitch02#ping
Protocol [ip]:
Target IP address: 10.128.136.21
Repeat count [5]: 50
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 50, 100-byte ICMP Echos to 10.128.136.21, timeout is 2 seconds:
!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!
Success rate is 84 percent (42/50), round-trip min/avg/max = 1/1/4 ms
CiscoSwitch02#

But when I ping the CCM 4.x there is no packet loss.

CCM 4.x

CiscoSwitch02#ping
Protocol [ip]:
Target IP address: 10.172.7.141
Repeat count [5]: 50
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 50, 100-byte ICMP Echos to 10.172.7.141, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (50/50), round-trip min/avg/max = 1/1/9 ms
CiscoSwitch02#

What is the reason for this. I have tried this at multiple locations and found the same result.

Thanks,

Vaijanath

[William Bell]

This is operating as designed.  It is a rudementary DoS prevention method.  ICMP packets from a Cisco IOS switch or router

actually are sent at a faster rate than a MS Windows workstation.  Therefore, the DoS prevention "feature" is triggered and the CUCM drops the packet.  We have seen even more than one ICMP echo dropped in a series.  So, this is expected behavior.

HTH.

Regards,
Bill

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