I have an IOS router (12.4) that I am adding a VPN tunnel to.  There are other active tunnels on this router (both ezvpn, site-to-site and GRE).  Everything appears to be working on both sides regarding phase 1/phase 2 negotiation, but packets that are being send from the PIX to the IOS router, while being encrypted and encapsulated do not appear to be being decrypted on the IOS end. I have spent many, many hours on trying to diagnose this and I am struggling - would appreciate any help. Show crypto isakmp sa on the IOS shows (IPs changed for security):  1.1.1.1 2.2.2.2 QM_IDLE              4    0 ACTIVE Show crypto ipsec sa on the IOS shows (IPs changed for security): local  ident (addr/mask/prot/port): (10.13.39.0/255.255.255.0/0/0)    remote ident (addr/mask/prot/port): (172.16.50.0/255.255.255.0/0/0)    current_peer 2.2.2.2 port 500      PERMIT, flags={origin_is_acl,}     #pkts encaps: 408, #pkts encrypt: 408, #pkts digest: 408    #pkts decaps: 0, #pkts decrypt: 0, #pkts verify: 0     #pkts compressed: 0, #pkts decompressed: 0     #pkts not compressed: 0, #pkts compr. failed: 0     #pkts not decompressed: 0, #pkts decompress failed: 0     #send errors 108, #recv errors 0      local crypto endpt.: 1.1.1.1, remote crypto endpt.: 2.2.2.2      path mtu 1500, ip mtu 1500, ip mtu idb FastEthernet0/0      current outbound spi: 0xBC3A7FC9(3157950409)      inbound esp sas:       spi: 0x2DF17FA(48175098)         transform: esp-3des esp-sha-hmac ,         in use settings ={Tunnel, }         conn id: 3003, flow_id: FPGA:3, crypto map: CustVPN         sa timing: remaining key lifetime (k/sec): (4553489/2310)         IV size: 8 bytes         replay detection support: Y         Status: ACTIVE      inbound ah sas:      inbound pcp sas:      outbound esp sas:       spi: 0xBC3A7FC9(3157950409)         transform: esp-3des esp-sha-hmac ,         in use settings ={Tunnel, }         conn id: 3004, flow_id: FPGA:4, crypto map: CustVPN         sa timing: remaining key lifetime (k/sec): (4553463/2310)         IV size: 8 bytes         replay detection support: Y         Status: ACTIVE      outbound ah sas:      outbound pcp sas: I am focusing in on the decapsulation/decryption and on why it is not happening.  Everything appears to be working on the PIX end. show crypto isakmp sa on the PIX shows (IPs changed for security):    Active SA: 1     Rekey SA: 0 (A tunnel will report 1 Active and 1 Rekey SA during rekey) Total IKE SA: 1 1   IKE Peer: 1.1.1.1     Type    : L2L             Role    : initiator     Rekey   : no              State   : MM_ACTIVE show crypto ipsec sa on the PIX shows (IPs changed for security): Crypto map tag: outside_map, seq num: 120, local addr: 2.2.2.2       access-list outside_cryptomap_120 permit ip 172.16.50.0 255.255.255.0 10.13.39.0 255.255.255.0       local ident (addr/mask/prot/port): (172.16.50.0/255.255.255.0/0/0)       remote ident (addr/mask/prot/port): (10.13.39.0/255.255.255.0/0/0)       current_peer: 1.1.1.1       #pkts encaps: 1030, #pkts encrypt: 1030, #pkts digest: 1030       #pkts decaps: 322, #pkts decrypt: 322, #pkts verify: 322       #pkts compressed: 0, #pkts decompressed: 0       #pkts not compressed: 1030, #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.: 2.2.2.2, remote crypto endpt.: 1.1.1.1       path mtu 1500, ipsec overhead 58, media mtu 1500       current outbound spi: 02DF17FA     inbound esp sas:       spi: 0xBC3A7FC9 (3157950409)          transform: esp-3des esp-sha-hmac none          in use settings ={L2L, Tunnel, }          slot: 0, conn_id: 36, crypto-map: outside_map          sa timing: remaining key lifetime (kB/sec): (4274981/1824)          IV size: 8 bytes          replay detection support: Y     outbound esp sas:       spi: 0x02DF17FA (48175098)          transform: esp-3des esp-sha-hmac none          in use settings ={L2L, Tunnel, }          slot: 0, conn_id: 36, crypto-map: outside_map          sa timing: remaining key lifetime (kB/sec): (4274939/1824)          IV size: 8 bytes          replay detection support: Y Everything seems ok to me but the IOS is not decrypting.  The other tunnels on the system are working fine.  Debugs do not show any errors. ... View more