- Silver, 250 points or more
I need some advice and best practice guidance, plus some reference material for the following case (novell alert).
Currently we are running a CallManager cluster 4.0(1)SR2a with the publisher and a subscriber in our datacenter. A second subscriber is located at another location (connection between datacenter and co-location is a 10Mbps MAN). This co-location also holds an IPCC 3.5.1 server. Three other co-locations use the cluster resources. All locations use a local gateway to the PSTN. The WAN in between all other co-locations and the datacenter is a MPLS VPN service with different classes of services for call-signaling and RTP streams. Everything is operational and working fine for a couple of years now.
Currently, the IP WAN in not used for intersite RTP streams, but we are in the works of implementing a new MPLS based WAN (new provider) which delivers QoS for less costs which will make intersite dialing over the IP WAN interesting for us. Also, we will have redundancy for the WAN by implementing a second router on a DSL which builds a GRE/IPSec encrypted tunnel to the second router in the datacenter. As a result it is very unlikely that the WAN will fail and that phones will loose connectivity to the CCM cluster. However, for some important sites we will still implement SRST in case the IP WAN fails (very unlikely, but still).
To save costs we want to split the number of e-phones over the two routers (otherwise the required platforms are to excessive) and as far as we understood so far this should be possible. However, documentation and best practice information is quite hard to find (and believe me, I've tried).
So far I figured that to achieve this I will need to configure two SRST references in CallManager and split the phones into two device pools. Then associate the two different SRTS references which the two devicepools to achieve the SRST split. This is the easy part, but now the hard part. Only one router holds the BRI or PRI interfaces to the PSTN so I need to setup dialpeers on the routers in order to get everything to route correctly while in SRST. So, the main question is, what would be the best practice and needed dialpeer configuration to achieve this?
Another thing I am strugling with is the phone load that I will need. We will be running IOS 12.4(6)T on the routers, so this is SRST 4 (if I am not mistaken). This together with CCM 4.0(1)SR2a, what would be the best phoneload for the 7940, 7960, 7920 and 7936 phones?
Any other information for guidance in this setup will be highly appreciated.