Im having some problems with a DMVPN connection on a Cisco 876.
It is connected to an ADSL line with PPPoE dialer.
The pppoe is 8 byte overhead and the DMVPN is 24 byte, which should be 1468 MTU.
However, i also have configured ipsec tunnel mode (default ios) on this and because of ipsec im having troubles doing the mtu math for max MTU on packets leaving/received on the tunnel interface. Configuration is as follow:
interface Tunnel xx
ip address x.x.x.x x.x.x.x
ip nhrp authentication xxxx
ip nhrp map multicast x.x.x.x
ip nhrp map x.x.x.x x.x.x.x
ip nhrp network-id 10
ip nhrp holdtime 300
ip nhrp nhs x.x.x.x
tunnel source DialerX
tunnel mode gre multipoint
tunnel key xxxxx
tunnel protection ipsec profile vpnprof
crypto isakmp policy 1
crypto isakmp key xxxxxxx address x.x.x.x x.x.x.x
crypto ipsec transform-set dmvpn-trans esp-3des esp-sha-hmac
crypto ipsec profile vpnprof
set transform-set dmvpn-trans
- How much MTU is max size i can get through here?
- And what would the optimal mtu be here?
- Should the Dialer interface be configured with any ip mtu at all? Its configured with "ip mtu 1492" in my configuration.
- Also, any good optimal tcp adjust-mss size?
Any help would be appreciated!