! Enable L2TP
! - Connect VPN clients to VRF private
! Must use "password" ("secret" won't work)
username roadwarrior password 0 <removed>
aaa authentication ppp l2tp-auth local-case
ip local pool l2tp-pool 10.1.11.100 10.1.11.199
vpdn enable
interface Virtual-Template1
ip unnumbered Loopback0
peer default ip address pool l2tp-pool
ppp mtu adaptive
ppp authentication ms-chap-v2 l2tp-auth
!
vpdn-group l2tp-group
! Default L2TP VPDN group
description L2TP clients
accept-dialin
protocol l2tp
virtual-template 1
!
no l2tp tunnel authentication
!
! ISAKMP policy:
! - OS X offers aes 256 and 128 (but not 192)
! - SHA1 is the default hash on Cisco IOS (does not show up in config)
! - OS X doesn't offer any of the PFS groups
crypto isakmp policy 50
encr aes 256
authentication pre-share
group 2
lifetime 14400
!
! Internet is connected to VRF cable
crypto keyring l2tp-ring vrf cable
pre-shared-key address 0.0.0.0 0.0.0.0 key <removed>
!
! IPsec policy
! - Match OS X proposal
crypto ipsec transform-set l2tp-transform esp-aes 256 esp-sha-hmac
mode transport
!
! Require IPsec for all L2TP traffic
!
ip access-list extended l2tp-access
permit udp any eq 1701 any
!
crypto dynamic-map l2tp-map 10
set nat demux
set transform-set l2tp-transform
match address l2tp-access
!
crypto map l2tp 10 ipsec-isakmp dynamic l2tp-map
interface Vlan6
crypto map l2tp
!
sip trunk to asterisk
If the call is terminating on the 2800 ( ie ip to tdm) there is no need to transcode….
It would just be a standard sip offer/answer dialog.
As long as one codec matches it would be fine.
If you have 2 ip legs you should look into cisco border element configs as an SBC.
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube/configuration/cube-book.html
You can then decide how to work the codec selection and how the cisco interacts( interferes may be a better term) with the media session between the 2 legs Transcoding would only be necessary if you have two IP legs and each leg needs to use a different codec.
Leg 1 g711a and leg2 g729 for example.
The 2800 can do this