Cisco ASA 5505 - Inside to Inside help

Posted on 2009-04-01
Last Modified: 2012-05-06
Greetings all!

I have a 5505 on  I need to access other switches and routers at our remote offices on networks and  When I try this from my machine, I get:

"Inbound TCP connection denied from to flags SYN  on interface inside"

Either this won't work because of the inherit ASA routing security or I need some NAT entries (or something else).  Any advice would be appreciated!   Thank you.

Results of "sh run":

ASA Version 8.0(4)23 
hostname ciscoasa
domain-name priority.local
interface Vlan1
 nameif inside
 security-level 100
 ip address 
interface Vlan2
 nameif outside
 security-level 0
 ip address 
interface Ethernet0/0
 switchport access vlan 2
interface Ethernet0/1
interface Ethernet0/2
interface Ethernet0/3
interface Ethernet0/4
interface Ethernet0/5
interface Ethernet0/6
interface Ethernet0/7
boot system disk0:/currentsoftware/asa804-23-k8.bin
ftp mode passive
clock timezone EST -5
clock summer-time EDT recurring
dns server-group DefaultDNS
 domain-name priority.local
pager lines 24
logging enable
logging timestamp
logging trap critical
logging asdm informational
logging host inside
logging permit-hostdown
mtu inside 1500
mtu outside 1500
ip verify reverse-path interface outside
icmp unreachable rate-limit 1 burst-size 1
icmp deny any outside
asdm image disk0:/currentsoftware/asdm-61557.bin
no asdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1
route outside 1
route inside 1
route inside 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00
timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00
timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute
timeout tcp-proxy-reassembly 0:01:00
dynamic-access-policy-record DfltAccessPolicy
aaa authentication ssh console LOCAL 
http server enable
http inside
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
crypto ipsec security-association lifetime seconds 28800
crypto ipsec security-association lifetime kilobytes 4608000
crypto ca trustpoint ASDM_TrustPoint0
 enrollment self
 subject-name CN=ciscoasa
 crl configure
telnet timeout 5
ssh inside
ssh timeout 5
ssh version 2
console timeout 0
dhcpd auto_config outside
threat-detection basic-threat
threat-detection scanning-threat shun except ip-address
threat-detection scanning-threat shun except ip-address
threat-detection scanning-threat shun except ip-address
threat-detection scanning-threat shun duration 3600
threat-detection statistics host
no threat-detection statistics access-list
no threat-detection statistics tcp-intercept
ntp server source outside prefer
class-map inspection_default
 match default-inspection-traffic
policy-map type inspect dns preset_dns_map
  message-length maximum 512
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map 
  inspect ftp 
  inspect h323 h225 
  inspect h323 ras 
  inspect rsh 
  inspect rtsp 
  inspect esmtp 
  inspect sqlnet 
  inspect skinny  
  inspect sunrpc 
  inspect xdmcp 
  inspect sip  
  inspect netbios 
  inspect tftp 
service-policy global_policy global
prompt hostname context 
: end

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Question by:knoxlogic
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LVL 43

Expert Comment

ID: 24039921
You need to set the hosts default gateway to and then make sure the router has a default route via the ASA.

You can enable same interface traffic but you are still going to have an issue with TCP connections.

Author Comment

ID: 24042102
I'm not sure I can do this, as is setup as our MPLS router, via our LEC.  We/I don't manage that.  
LVL 43

Accepted Solution

JFrederick29 earned 500 total points
ID: 24042141
Okay, do you have a layer3 switch on the network?

Here's the problem when you attempt to communicate to the remote network with your current setup.

TCP SYN from to goes to ASA then to MPLS router then to client (okay so far)
TCP SYN ACK from goes to MPLS router then to (bypassing ASA).
TCP ACK from to goes to ASA and the ASA denies the connection since it didn't see the SYN ACK.

If you can't use the MPLS router as the gateway for the subnet and you don't have a layer 3 switch on the subnet, the only other alternative is to add routes to every PC for the remote networks:

route add mask -p
route add mask -p

Author Closing Comment

ID: 31565333
I'll have to get a Layer3 switch to get this working "correctly", but for now, your route statements did the trick.  Thanks!

FYI... for anyone seeing this issue and running these route commands in Windows Vista with UAC turned on, you'll have to make sure you run "cmd" as an administrator (being logged in as one doesn't work).  To do this:

start -> type "cmd" -> ctrl-shift-enter

That will put you in "admin" mode for command line.

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