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ASA 8.4(2) - Weirdest NAT issue on IPSec Tunnel

Helloo All,

This has to be the most weirdest issue I have seen since the past year on my ASA.

I have an ASA 5540 running the 8.4(2) code without any issues until I stumbled upon this problem last week and I have spent sleepless nights with no resolution! So, take a deep breath and here is a brief description of my setup and the problem:

A Simple IPSEC tunnel between my ASA 5540 8.4(2) and a Juniper SSG 140 screen OS 6.3.0r9.0(route based VPN)

The tunnel comes up without any issues but the ASA refuses to encrypt the traffic but decrypts it with GLORY!

below are some debug outputs, show outputs and a packet tracer output which also has an explanation of my WEIRD NAT issue:

my setup - ( I wont get into the tunnel encryption details as my tunnel negotiations are piss perfect and comes up right off the bat when the ASA is configured as answer only)

CISCO ASA - IPSec networking details

LOCAL NETWORK - 10.2.4.0/28

REMOTE NETWORK - 192.168.171.8/32

JUNIPER SSG 140 - IPSec networking details

PROXY ID:

LOCAL NETWORK - 192.168.171.8/32

REMOTE NETWORK - 10.2.4.0/28

HOSTNAME# sh cry ipsec sa peer <JUNIPER SSG PEER>

peer address: <JUNIPER SSG PEER>

    Crypto map tag: outside_map, seq num: 5, local addr: <local peer>

      access-list outside_cryptomap_4 extended permit ip 10.2.4.0 255.255.255.240 host 192.168.171.8

      local ident (addr/mask/prot/port): (10.2.4.0/255.255.255.240/0/0)

      remote ident (addr/mask/prot/port): (192.168.171.8/255.255.255.255/0/0)

      current_peer: <JUNIPER SSG PEER>

      #pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0

      #pkts decaps: 72, #pkts decrypt: 72, #pkts verify: 72

      #pkts compressed: 0, #pkts decompressed: 0

      #pkts not compressed: 0, #pkts comp failed: 0, #pkts decomp failed: 0

      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0

      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0

      #send errors: 0, #recv errors: 0

      local crypto endpt.: <local peer>/0, remote crypto endpt.: <juniper remote peer>/0

      path mtu 1500, ipsec overhead 58, media mtu 1500

      current outbound spi: 5041C19F

      current inbound spi : 0EC13558

    inbound esp sas:

      spi: 0x0EC13558 (247543128)

         transform: esp-3des esp-sha-hmac no compression

         in use settings ={L2L, Tunnel, }

         slot: 0, conn_id: 22040576, crypto-map: outside_map

         sa timing: remaining key lifetime (sec): 3232

         IV size: 8 bytes

         replay detection support: Y

         Anti replay bitmap:

          0xFFFFFFFF 0xFFFFFFFF

    outbound esp sas:

      spi: 0x5041C19F (1346486687)

         transform: esp-3des esp-sha-hmac no compression

         in use settings ={L2L, Tunnel, }

         slot: 0, conn_id: 22040576, crypto-map: outside_map

         sa timing: remaining key lifetime (sec): 3232

         IV size: 8 bytes

         replay detection support: Y

         Anti replay bitmap:

          0x00000000 0x00000001

VPN CONTEXTS for this IPSEC tunnel:

HOSTNAME# sh asp table vpn-context det

VPN CTX  = 0x0742E6BC

Peer IP  = 192.168.171.8

Pointer  = 0x78C94BF8

State    = UP

Flags    = ENCR+ESP

SA       = 0x9C28B633

SPI      = 0x5041C19D

Group    = 0

Pkts     = 0

Bad Pkts = 0

Bad SPI  = 0

Spoof    = 0

Bad Crypto = 0

Rekey Pkt  = 0

Rekey Call = 0

VPN Filter = <none>

VPN CTX  = 0x07430D3C

Peer IP  = 192.168.1.8

Pointer  = 0x78F62018

State    = UP

Flags    = DECR+ESP

SA       = 0x9C286E3D

SPI      = 0x9B6910C5

Group    = 1

Pkts     = 297

Bad Pkts = 0

Bad SPI  = 0

Spoof    = 0

Bad Crypto = 0

Rekey Pkt  = 0

Rekey Call = 0

VPN Filter = <none>


access-list outside_cryptomap_4 extended permit ip 10.2.4.0 255.255.255.240 host 192.168.171.8

nat (inside,outside) source static Ren-vers Ren-vers destination static Peer-Host Peer-Host no-proxy-arp route-lookup

object network Ren-vers

subnet 10.2.4.0 255.255.255.240

object network Peer-Host

host 192.168.171.8

sh cry ipsec sa

   IKE Peer: <remote peer>

    Type    : L2L             Role    : responder

    Rekey   : no              State   : MM_ACTIVE

packet tracer output extract for a packet being sent from the 10.2.4.0/28 network to 192.168.171.8 host

Phase: 7

Type: VPN

Subtype: encrypt

Result: ALLOW

Config:

Additional Information:

Forward Flow based lookup yields rule:

out id=0x7789d788, priority=70, domain=encrypt, deny=false

        hits=2, user_data=0x742e6bc, cs_id=0x7ba38680, reverse, flags=0x0, protocol=0

        src ip/id=10.2.4.0, mask=255.255.255.240, port=0

        dst ip/id=192.168.171.8, mask=255.255.255.255, port=0, dscp=0x0

        input_ifc=any, output_ifc=outside

THE VPN contexts match for the encrytpion+encapsulation.

A Full packet tracer output for a packet from the 10.2.4.1 255.255.255.255 network to host 192.168.171.8:

Phase: 1

Type: ACCESS-LIST

Subtype:

Result: ALLOW

Config:

Implicit Rule

Additional Information:

Forward Flow based lookup yields rule:

in  id=0x77ebd1b0, priority=1, domain=permit, deny=false

        hits=3037156, user_data=0x0, cs_id=0x0, l3_type=0x8

        src mac=0000.0000.0000, mask=0000.0000.0000

        dst mac=0000.0000.0000, mask=0100.0000.0000

        input_ifc=inside, output_ifc=any

Phase: 2

Type: ROUTE-LOOKUP

Subtype: input

Result: ALLOW

Config:

Additional Information:

in   192.168.171.0     255.255.255.0   outside

Phase: 3

Type: IP-OPTIONS

Subtype:

Result: ALLOW

Config:

Additional Information:

Forward Flow based lookup yields rule:

in  id=0x77ec1030, priority=0, domain=inspect-ip-options, deny=true

        hits=212950, user_data=0x0, cs_id=0x0, reverse, flags=0x0, protocol=0

        src ip/id=0.0.0.0, mask=0.0.0.0, port=0

        dst ip/id=0.0.0.0, mask=0.0.0.0, port=0, dscp=0x0

        input_ifc=inside, output_ifc=any

Phase: 4

Type:

Subtype:

Result: ALLOW

Config:

Additional Information:

Forward Flow based lookup yields rule:

in  id=0x7c12cb18, priority=18, domain=flow-export, deny=false

        hits=172188, user_data=0x78b1f438, cs_id=0x0, use_real_addr, flags=0x0,

        src ip/id=0.0.0.0, mask=0.0.0.0, port=0

        dst ip/id=0.0.0.0, mask=0.0.0.0, port=0, dscp=0x0

        input_ifc=inside, output_ifc=any

Phase: 5

Type: NAT

Subtype:

Result: ALLOW

Config:

nat (inside,outside) source static Ren-vers Ren-vers destination static Peer-Host Peer-Host no-proxy-arp route-lookup

Additional Information:

Static translate 10.2.4.1/2700 to 10.2.4.1/2700

Forward Flow based lookup yields rule:

in  id=0x77e0a878, priority=6, domain=nat, deny=false

        hits=9, user_data=0x7b7360a8, cs_id=0x0, use_real_addr, flags=0x0, proto

        src ip/id=10.2.4.1, mask=255.255.255.240, port=0

        dst ip/id=192.168.171.8, mask=255.255.255.255, port=0, dscp=0x0

        input_ifc=inside, output_ifc=outside

(this is the weird  NAT issue I am seeing. I see the hits count is incrementing only when I run the packet tracer even thugh I have constant pings(traffic) from the 192.168.171.8 host to the 10.2.4.1/28) - please see the packet capture that i have pasted after this section)

Phase: 6

Type: VPN

Subtype: encrypt

Result: ALLOW

Config:

Additional Information:

Forward Flow based lookup yields rule:

out id=0x7b8751f8, priority=70, domain=encrypt, deny=false

        hits=3, user_data=0x7432b74, cs_id=0x7ba38680, reverse, flags=0x0, proto

        src ip/id=10.2.4.1, mask=255.255.255.240, port=0

        dst ip/id=192.168.171.8, mask=255.255.255.255, port=0, dscp=0x0

        input_ifc=any, output_ifc=outside

Phase: 7

Type: VPN

Subtype: ipsec-tunnel-flow

Result: ALLOW

Config:

Additional Information:

Reverse Flow based lookup yields rule:

in  id=0x78b0c280, priority=69, domain=ipsec-tunnel-flow, deny=false

        hits=154, user_data=0x7435f94, cs_id=0x0, reverse, flags=0x0, protocol=0

        src ip/id=192.168.171.8, mask=255.255.255.255, port=0

        dst ip/id=10.2.4.1, mask=255.255.255.240, port=0, dscp=0x0

        input_ifc=outside, output_ifc=any

Phase: 8

Type: IP-OPTIONS

Subtype:

Result: ALLOW

Config:

Additional Information:

Reverse Flow based lookup yields rule:

in  id=0x77e7a510, priority=0, domain=inspect-ip-options, deny=true

        hits=184556, user_data=0x0, cs_id=0x0, reverse, flags=0x0, protocol=0

        src ip/id=0.0.0.0, mask=0.0.0.0, port=0

        dst ip/id=0.0.0.0, mask=0.0.0.0, port=0, dscp=0x0

        input_ifc=outside, output_ifc=any

Phase: 9

Type: FLOW-CREATION

Subtype:

Result: ALLOW

Config:

Additional Information:

New flow created with id 119880921, packet dispatched to next module

Module information for forward flow ...

snp_fp_tracer_drop

snp_fp_inspect_ip_options

snp_fp_tcp_normalizer

snp_fp_translate

snp_fp_adjacency

snp_fp_encrypt

snp_fp_fragment

snp_ifc_stat

Module information for reverse flow ...

snp_fp_tracer_drop

snp_fp_inspect_ip_options

snp_fp_ipsec_tunnel_flow

snp_fp_translate

snp_fp_tcp_normalizer

snp_fp_adjacency

snp_fp_fragment

snp_ifc_stat

Result:

input-interface: inside

input-status: up

input-line-status: up

output-interface: outside

output-status: up

output-line-status: up

Action: allow


HOSTNAME# sh cap cap1

8 packets captured

   1: 12:26:53.376033 192.168.10.252 > 10.2.4.1: icmp: echo request

   2: 12:26:53.376597 10.2.4.1 > 192.168.10.252: icmp: echo reply

   3: 12:26:56.487905 192.168.171.8 > 10.2.4.1: icmp: echo request

   4: 12:27:01.489217 192.168.171.8 > 10.2.4.1: icmp: echo request

   5: 12:27:03.378245 192.168.10.252 > 10.2.4.1: icmp: echo request

   6: 12:27:03.378825 10.2.4.1 > 192.168.10.252: icmp: echo reply

   7: 12:27:06.491597 192.168.171.8 > 10.2.4.1: icmp: echo request

   8: 12:27:11.491856 192.168.171.8 > 10.2.4.1: icmp: echo request

8 packets shown

As you can see, there is no echo reply packet at all as the packet is not being encapsulated while it is being sent back.

I have been going madddd with this. Also, this is a live production multi tenant firewall with no issues at all apart from this shitty ipsec tunnel to a juniper!!

Also, the 192.168.10.0/24 is another IPSec tunnel remote network to this 10.2.4.0/28 network and this IPSEC tunnel has a similar Juniper SSG 140 screen os 6.3.0r9.0 at the remote end and this woks like a charm without any issues, but the 171 is not being encrypted by the ASA at all.

If anybody could help me out, that would be greattt!!

Thanks heaps!






2 REPLIES
New Member

ASA 8.4(2) - Weirdest NAT issue on IPSec Tunnel

Will a reboot of the ASA manke any difference at all? This is in a hosting environment with 24x7 and reboots can be taken to the management under exceptional circumstances and sure fixes.. any suggestions here, please?

Any CISCO TAC guys here?

Cheers..

New Member

Re: ASA 8.4(2) - Weirdest NAT issue on IPSec Tunnel

The problem is related to my L3 switch.. something must have gone wrong with the control plane on the active one and it is not routing right and it hasn't failed over yet..

i changed the default gateway on my inside peer to point to the inside interface of the ASA and it works with full glory. oh sweet baby jesuss.. feels soo good..i knew i had the asa down pat!

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