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New Member

router 1760 config with GRE and IPsec, outgoing encrypted traffic problems


I have a 1760 router connected to the internet via ADSL. The other route end connects to a pc that runs a server sending packets through the router to the internet. The PC private local ip is the router is and the static public ip address from the ISP is x.x.x.x

I have setup a GRE tunnel to connect to another company, with IPsec as show in the configuration below

The problem i have has to do with the traffic directed through the tunnel to the internet. I want to send all packets with destination 10.20.44.* through the tunnel When i send packets from the server running in the PC behind the router, i can see packets from to The problem comes after i sent 2 such packets, i can no longer receive a correct answer from the sestination ( i sent them.

So every time i can send just 2 packets out to the net correctly, through the tunnel with destination 10.x.x.1 and source 172.x.x.1. I have found that when i delete the ip route command that directs traffic in the tunnel0 and REAPPLY the same ip route immediatly after deleting it, i can again send just 2 more packets and receive answer, then again stops.

Also if i wait long enough (about 10minutes) after the 2 packets have been sent, i can send one more packet then stops again.

I also receive packets from them correctly, so i suspect it has to do with ipsec, since it is the only thing that gets in the way, and the tunnel works fine for the first 2 packets.

My config.

version 12.3

no aaa new-model

no ip subnet-zero

ip dhcp excluded-address 172.x.x.1

ip dhcp pool 0

network 172.x.x.x x.255.0.0


dns-server 195.x.x.x.170.2.1

ip cef

ip audit notify log

ip audit po max-events 100

ip ssh break-string

no ftp-server write-enable

no scripting tcl init

no scripting tcl encdir

crypto isakmp policy 1

hash md5

authentication pre-share

group 2

crypto isakmp key * address 195.x.x.104

crypto ipsec transform-set cm-transformset-1 esp-des esp-md5-hmac

crypto map cm-cryptomap 1 ipsec-isakmp

set peer

set transform-set cm-transformset-1

match address cosmote

interface Tunnel0

description tunnel to cosmote

ip unnumbered FastEthernet0/0

tunnel source

tunnel destination 10.x.x.11

interface ATM0/0

no ip address

no ip mroute-cache

no atm ilmi-keepalive

pvc 8/35

encapsulation aal5mux ppp dialer

dialer pool-member 1

dsl operating-mode auto

crypto map cm-cryptomap

interface FastEthernet0/0

ip address 172.16.x.x x.255.0.0

ip nat inside

speed auto

interface Dialer1

ip address negotiated

ip nat outside

encapsulation ppp

dialer pool 1

no cdp enable

ppp authentication pap callin

ppp pap sent-username ** password 0 **

ppp multilink

crypto map cm-cryptomap


ip nat pool ourpool netmask

ip nat inside source route-map nonat pool ourpool overload

ip nat inside source static tcp 7393 7393 extendable

ip classless

ip route Dialer1

ip route Tunnel0

ip access-list extended cosmote

permit ip host host

access-list 175 deny ip

access-list 175 permit ip any

access-list 175 deny ip


route-map nonat permit 10

match ip address 175


Thanks a lot

New Member

Re: router 1760 config with GRE and IPsec, outgoing encrypted tr

Everything looks fine for me. any update on this ?

New Member

Re: router 1760 config with GRE and IPsec, outgoing encrypted tr

Well the problem is still unresolved.

I have found some more things though. When i shut the tunnel and turn it on i can send 2 packets, and get answer. Then the rest are problematic.

When i CAN send and receive, the debug at the other end i try to communicate sees the IPsec first, then the GRE and then the inside packet from to When i CAN'T send anymore, the debugger on the other end sees packets with IPsec, then GRE and after opening GRE sees AGAIN IPsec packet with source and destination instead of the inside network packets from to

What i want is NOT to encrypt the inside packet of the GRE, but the gre itself only. This is the problem mainly.

I have tryed to put gre instead of ip in the ipsec access-list "extended cosmote" but the connection fails completly either side. I have tryed to DENY the source and destination and does not work.

How can i prevent the packets from FastEthernet0/0 beeing encrypted ??? I suspect the ip route command directing the data through the tunnel tells the router to encrypt that data automatically. But why the access-list does not work?

Thanks again