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Having trouble getting a very simple site-to-site VPN going

The headend is an ASA5510 running 7.2(2).

I will post the config if requested, but here is the gist of it:

I have a nat exempt ACL and a corresponding nat 0 statement

I have an identical acl for the crypto map

I have sysopt connection permit-vpn

I have an appropriate transform set

I have a crypto map defined and applied. (includes a dynmap for remote users, dynmap is seq 99, site-to-site is seq 10)

I have isakmp enable outside

I have appropriate isakmp policies defined.

I have a tunnel group with the IP address of the peer defined and the shared key defined.

I have done numerous clear xlates and clear ipsec/isakmp sa.

When interesting traffic arrives at the interface, a debug crypto isakmp or ipsec shows no activity.

A packet trace runs and succeeds until:

Phase: 8

Type: VPN

Subtype: encrypt

Result: DROP


Additional Information:

Forward Flow based lookup yields rule:

out id=0x45c8ec0, priority=70, domain=encrypt, deny=false

hits=1, user_data=0x0, cs_id=0x3c4c550, reverse, flags=0x0, protocol=0

src ip=, mask=, port=0

dst ip=, mask=, port=0


input-interface: alarms-dmz

input-status: up

input-line-status: up

output-interface: outside

output-status: up

output-line-status: up

Action: drop

Drop-reason: (acl-drop) Flow is denied by configured rule

I am stumped, I've done this 100 times and this one is killing me. Random thoughts:

I've cleared the service policies I had applied

I've cleared the default group policy.

The "interesting" traffic in this case originates on a "DMZ" interface. I've tried security 100 and 80. The interface has no ACLs applied to it in either direction.

Any ideas??


Re: Having trouble getting a very simple site-to-site VPN going

Probably want to post the clean configs. One quick thought is that your nat exemption might look like nat (inside) 0 instead of nat (dmz) 0, just a guess of course.

Community Member

Re: Having trouble getting a very simple site-to-site VPN going

Thanks for the reply! The NAT statement references the correct interface, but a good guess. Here is what I think is the salient part of the configuration:

access-list alarms-no-nat extend permit ip host

access-list telsa extend permit ip host

nat (alarms-dmz) 0 access-list alarms-no-nat

sysopt connection permit-vpn

crypto ipsec transform-set site-to-site esp-aes-256 esp-sha-hmac

crypto map melford 10 match address telsa

crypto map melford 10 set peer

crypto map melford 10 set transform-set site-to-site

crypto map melford 99 ipsec-isakmp dynamic dynmap

crypto map melford interface outside

isakmp enable outside

isakmp policy 10 authentication pre-share

isakmp policy 10 encryption aes-256

isakmp policy 10 hash sha

isakmp policy 10 group 5

isakmp policy 10 lifetime 86400

isakmp policy 65535 authentication pre-share

isakmp policy 65535 encryption 3des

isakmp policy 65535 hash sha

isakmp policy 65535 group 2

isakmp policy 65535 lifetime 86400

tunnel-group type ipsec-l2l

tunnel-group ipsec-attributes

pre-shared-key [redacted]


clear xlate

**clear ipsec sa

**clear isakmp sa

I stumbled across a page that states the packet tracer won't work if the SA is not already established, so I guess that is not a valid test.

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