Troubleshooting Cisco ASA customer gateway device connectivity
When you troubleshoot the connectivity of a Cisco customer gateway device, consider IKE, IPsec, and routing. You can troubleshoot these areas in any order, but we recommend that you start with IKE (at the bottom of the network stack) and move up.
Important
Some Cisco ASAs only support Active/Standby mode. When you use these Cisco ASAs, you can have
only one active tunnel at a time. The other standby tunnel becomes active only if
the first tunnel becomes unavailable. The standby tunnel might produce the following
error in your log files, which can be ignored: Rejecting IPSec tunnel: no
matching crypto map entry for remote proxy 0.0.0.0/0.0.0.0/0/0 local proxy
0.0.0.0/0.0.0.0/0/0 on interface outside .
IKE
Use the following command. The response shows a customer gateway device with IKE configured correctly.
ciscoasa#show crypto isakmp sa
Active SA: 2
Rekey SA: 0 (A tunnel will report 1 Active and 1 Rekey SA during rekey)
Total IKE SA: 2
1 IKE Peer: AWS_ENDPOINT_1
Type : L2L Role : initiator
Rekey : no State : MM_ACTIVEYou should see one or more lines containing an src value for the remote
gateway that is specified in the tunnels. The state value should be
MM_ACTIVE and status should be ACTIVE.
The absence of an entry, or any entry in another state, indicates that IKE is not
configured properly.
For further troubleshooting, run the following commands to enable log messages that provide diagnostic information.
router#term monrouter#debug crypto isakmp
To disable debugging, use the following command.
router#no debug crypto isakmp
IPsec
Use the following command. The response shows a customer gateway device with IPsec configured correctly.
ciscoasa#show crypto ipsec sa
interface: outside
Crypto map tag: VPN_crypto_map_name, seq num: 2, local addr: 172.25.50.101
access-list integ-ppe-loopback extended permit ip any vpc_subnet subnet_mask
local ident (addr/mask/prot/port): (0.0.0.0/0.0.0.0/0/0)
remote ident (addr/mask/prot/port): (vpc_subnet/subnet_mask/0/0)
current_peer: integ-ppe1
#pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0
#pkts decaps: 0, #pkts decrypt: 0, #pkts verify: 0
#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.: 172.25.50.101, remote crypto endpt.: AWS_ENDPOINT_1
path mtu 1500, ipsec overhead 74, media mtu 1500
current outbound spi: 6D9F8D3B
current inbound spi : 48B456A6
inbound esp sas:
spi: 0x48B456A6 (1219778214)
transform: esp-aes esp-sha-hmac no compression
in use settings ={L2L, Tunnel, PFS Group 2, }
slot: 0, conn_id: 4710400, crypto-map: VPN_cry_map_1
sa timing: remaining key lifetime (kB/sec): (4374000/3593)
IV size: 16 bytes
replay detection support: Y
Anti replay bitmap:
0x00000000 0x00000001
outbound esp sas:
spi: 0x6D9F8D3B (1839172923)
transform: esp-aes esp-sha-hmac no compression
in use settings ={L2L, Tunnel, PFS Group 2, }
slot: 0, conn_id: 4710400, crypto-map: VPN_cry_map_1
sa timing: remaining key lifetime (kB/sec): (4374000/3593)
IV size: 16 bytes
replay detection support: Y
Anti replay bitmap:
0x00000000 0x00000001For each tunnel interface, you should see both inbound esp sas and
outbound esp sas. This assumes that an SA is listed (for example,
spi: 0x48B456A6), and that IPsec is configured correctly.
In Cisco ASA, the IPsec only comes up after interesting traffic (traffic that should be encrypted) is sent. To always keep the IPsec active, we recommend configuring an SLA monitor. The SLA monitor continues to send interesting traffic, keeping the IPsec active.
You can also use the following ping command to force your IPsec to start negotiation and go up.
pingec2_instance_ip_address
Pinging ec2_instance_ip_address with 32 bytes of data:
Reply from ec2_instance_ip_address: bytes=32 time<1ms TTL=128
Reply from ec2_instance_ip_address: bytes=32 time<1ms TTL=128
Reply from ec2_instance_ip_address: bytes=32 time<1ms TTL=128
Ping statistics for 10.0.0.4:
Packets: Sent = 3, Received = 3, Lost = 0 (0% loss),
Approximate round trip times in milliseconds:
Minimum = 0ms, Maximum = 0ms, Average = 0msFor further troubleshooting, use the following command to enable debugging.
router#debug crypto ipsec
To disable debugging, use the following command.
router#no debug crypto ipsec
Routing
Ping the other end of the tunnel. If this is working, then your IPsec should be established. If this is not working, check your access lists, and refer to the previous IPsec section.
If you are not able to reach your instances, check the following information.
-
Verify that the access list is configured to allow traffic that is associated with the crypto map.
You can do this using the following command.
ciscoasa#show run cryptocrypto ipsec transform-set transform-amzn esp-aes esp-sha-hmac crypto map VPN_crypto_map_name 1 match address access-list-name crypto map VPN_crypto_map_name 1 set pfs crypto map VPN_crypto_map_name 1 set peerAWS_ENDPOINT_1AWS_ENDPOINT_2crypto map VPN_crypto_map_name 1 set transform-set transform-amzn crypto map VPN_crypto_map_name 1 set security-association lifetime seconds 3600 -
Check the access list using the following command.
ciscoasa#show run access-list access-list-nameaccess-list access-list-name extended permit ip anyvpc_subnetsubnet_mask -
Verify that the access list is correct. The following example access list allows all internal traffic to the VPC subnet 10.0.0.0/16.
access-list access-list-name extended permit ip any 10.0.0.0 255.255.0.0 -
Run a traceroute from the Cisco ASA device, to see if it reaches the Amazon routers (for example,
AWS_ENDPOINT_1/AWS_ENDPOINT_2).If this reaches the Amazon router, then check the static routes that you added in the Amazon VPC console, and also the security groups for the particular instances.
For further troubleshooting, review the configuration.
