07-26-2008 08:55 PM - edited 03-06-2019 12:28 AM
Hi,
This is my topology:
R2811----Cat3750----CE500----(IP Phone+PC).
Call between IP Phone and IP Phone is very well but from IP Phone and PSTN through R2811 is intermittent.
When i ping from router 2811 to ip phones, i get 5 success and 1 fail.
All port on CE500 are configured as IP Phone+Deskop 100/full. giga ports connected to Cat3750 are switch ports 1000/full with native vlan data vlan.
I don't what is the reason of this issue.
07-27-2008 05:05 PM
i have actually seen the same issues and was wondering the reason. This is a design issue and not a configuration issue.
This is because the IP phones have been designed to only reply to an echo every 10ms, in order to withstand Denial of Service (DoS) attacks. A Cisco IOS gateway sends echos more frequently so one out of two will timeout. This is not the case for a PC since the time between two echos is greater than 10ms.
From this link:
http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a008010edb8.shtml
07-28-2008 12:59 PM
well, but this is not happening exactly, when Pin from the R2811 to IP Phone the result as below:
Promo7_CoreRouter#ping 172.29.0.87 source 172.29.0.1 repeat 100
Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 172.29.0.87, timeout is 2 seconds:
Packet sent with a source address of 172.29.0.1
!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!!!!!!!!.!!!!!.!!!!!.!
!!!!.!!!!!.!!!!!.!!!!!.!!!!!.!
Success rate is 84 percent (84/100), round-trip min/avg/max = 1/1/4 ms
Promo7_CoreRouter#
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