hello,
as per this link :
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/8_0_2/ccmsys/a05mtp.html#wp1041278
This type supports Cisco 2600XM, Cisco 2691, Cisco 3725, Cisco 3745, and Cisco 3660 Access Routers and the following MTP cases:
•For software-only implementation that does not use DSP but has the same packetization time for devices that support G.711 to G.711 or G.729 to G.729 codecs, this implementation can support up to 500 sessions per gateway.
•For a hardware-only implementation with DSP for devices that use G.711, G.729a, and G.729b codecs, 200 sessions can occur per NM-HDV2, and 48 sessions can occur per NM-HD.
so the above GWs can handle upto 500 Sessions if they were software only.
thanks
Khaled