I have configured a Lan-to-lan VPN between one Cisco 2811 with ADSL interface at the branch office and one PIX 515 connected to a 1721 with a ADSL interface at the HQ office.
The VPN is being used for voice communication between two CME 3.2 systems.
I have some problems with this setup because some calls are dropping after some minutes of conversation.
I have been monitoring the traffic produced by a conversation and I have seen that only one G.729 call is consuming over 40-50 kbps with VAD enabled.
Why it's consuming so much bandwidth ? I know that ipsec adds some headers but so much ?
Could it be related to packet fragmentation, MTU, or somethig like this ?
This is the interface configuration :
interface ATM0/1/0.1 point-to-point
ip address 81.44.x.x 255.255.255.128
crypto map vpn
vbr-nrt 640 640 1
protocol ip inarp
service-policy output output
ATM0/1/0.1 is up, line protocol is up
Hardware is DSLSAR (with Alcatel ADSL Module)
Internet address is 81.44.x.x/25
MTU 4470 bytes, BW 640 Kbit, DLY 800 usec,
reliability 255/255, txload 14/255, rxload 29/255
577351 packets input, 149329694 bytes
562564 packets output, 82825948 bytes
I am attaching a SNMP graphic of the bandwidth used for one g.729 voice call.
Any ideas ??