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New Member

Losing every 6th pings to 7941G

Have a 7941G configured as auto/auto to a 3560 10/100 switch also on auto/auto.

The port is running a 100 full. There are no errors, collisions or queue drops. There is very little traffic on the port, and no PC connectd to the phone.

When i ping the phone from the switch or router i loose every 6th ping. Even if i set a timeout to 20seconds, the pings just never come back - yet there are no errors on the switch port or on phone NIC to suggest a problem.

Tried different 7941 phones and differnet cables and still get same problem - yet the performance and voice quality of the phone is fine.

I think the phone is programmed to drop pings periodically - is this right?

When pinging with a Windows PC (which leave a bigger gap between pings) i don't get the drops.

The phone is on CME and running the latest phone code that was bundled with 12.4(4)XC2

This behaviour does not happen with older phones like 7902 that only work at 10/half.

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: Losing every 6th pings to 7941G

Cisco UC servers rate limit icmp packets

admin:utils firewall ipv4 list

.

.

DROP       all  --  0.0.0.0/0            0.0.0.0/0           state INVALID
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8 limit: avg 10/sec burst 5
LOG        icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8 limit: avg 1/min burst 5 LOG flags 0 level 4 prefix `ping flood '
DROP       icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8

.

.

This behavior can be duplicated with a ping flood (ping -f) from a linux box

I assume this is a normal and expected response for the VoIP devices

5 REPLIES
New Member

Re: Losing every 6th pings to 7941G

New Member

Re: Losing every 6th pings to 7941G

I see similar issues where pings issued from IOS to a device on voice vlan (in this case Avaya VOIP sets) lose every 3rd packet consistently (33% packet loss). This is only for IOS pings (extended or not). IOS pings to a data device extended from the Avaya set...on a non-voice vlan...lose no packets. Ports are also running 100 full.

There is apparently no voice loss and no pings are lost when launched from LAN attached PCs.

Can someone help me understand what is happening in the IOS to explain the behavior?

New Member

Re: Losing every 6th pings to 7941G

I see this too. In addition, I have seen this behavior also when pinging CUCM servers (6.1.3), Unity Connection servers. However, when pinging Unity 5 servers (Windows-based), I do not see this behavior.

New Member

Re: Losing every 6th pings to 7941G

Cisco UC servers rate limit icmp packets

admin:utils firewall ipv4 list

.

.

DROP       all  --  0.0.0.0/0            0.0.0.0/0           state INVALID
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           state RELATED,ESTABLISHED
ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8 limit: avg 10/sec burst 5
LOG        icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8 limit: avg 1/min burst 5 LOG flags 0 level 4 prefix `ping flood '
DROP       icmp --  0.0.0.0/0            0.0.0.0/0           icmp type 8

.

.

This behavior can be duplicated with a ping flood (ping -f) from a linux box

I assume this is a normal and expected response for the VoIP devices

Re: Losing every 6th pings to 7941G

Yes, this is expected behavior for most Linux-based UC appliances and phones (not sure what firmware this was first included with).  It's essentially a way to prevent a DoS attack on a UC server or phone.

Hailey

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