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New Member

ASA 5505 9.1(2) NAT/return traffic problems

As part of an office move we upgraded our ASA to 9.1(2) and have been having what seem to be NAT problems with some services ever since. These problems manifest themselves with return traffic. For example, network time sync (NTP, port 123) works fine from the ASA, but hosts on the inside network cannot access external NTP servers (ntpq -pe shows all servers stuck in .INIT. status), creating problems with drifting clocks. Services like XBox Live also do not work; the XBox device can contact the internet, but return traffic from the service never gets back to the device.

For NTP specifically, I've tried allowing NTP 123 through the firewall, but it doesn't help. Conceptually, this should not be required since an inside host is initiating the connection and the NAT rules "should" allow the return packets. To further muddy the waters around NTP, a Linux VM CAN get NTP if it's network adapter is in NAT mode (so it's NAT'ing through the host workstation, then through the Cisco) but CAN NOT get NTP if the adapter is running in bridged mode (so the VM is talking directly to the ASA as if it were just another machine on the inside network).

I've stripped down the ASA config to the basics level, but still can't get this resolved. The main symptom of the problem is that if I disable the access-list rules around ICMP, I'll see lots of ICMP warnings in the ASA logs, which seems to indicate that there are traffic problems communiating with the inside hosts. I've narrowed the problem down to the ASA since replacing the device with a simple Netgear consumer-grade "firewall" lets all this traffic flow just fine.

Network is extremely basic:

DHCP ASSIGNED IP from ISP <----------> ASA <-----------------> inside (192.168.50.X)


                                                                 |----------------------- guest vlan (10.0.1.X)

show running-config:

Result of the command: "show running-config"

: Saved


ASA Version 9.1(2)


hostname border


enable password aaa encrypted

passwd bbb encrypted



interface Ethernet0/0

switchport access vlan 2


interface Ethernet0/1

switchport trunk allowed vlan 1,3

switchport trunk native vlan 1

switchport mode trunk


interface Ethernet0/2


interface Ethernet0/3


interface Ethernet0/4


interface Ethernet0/5


interface Ethernet0/6


interface Ethernet0/7


interface Vlan1

nameif inside

security-level 100

ip address


interface Vlan2

nameif outside

security-level 0

ip address dhcp setroute


interface Vlan3

nameif Guest-VLAN

security-level 10

ip address


boot system disk0:/asa912-k8.bin

boot system disk0:/asa911-k8.bin

boot system disk0:/asa831-k8.bin

ftp mode passive

clock timezone EST -5

clock summer-time EDT recurring

dns domain-lookup outside

dns server-group DefaultDNS


domain-name domain

same-security-traffic permit inter-interface

object network obj_any


object network Guest-WLAN


description Interent access for guest Wireless

object network xbox-nat-tcp3074


object network xbox-nat-udp3074


object network xbox-nat-udp88


object service xbox-live-88

service udp destination eq 88

object network xbox


object network obj-inside


object network obj-xbox


object network plex-server


object network ubuntu-server


description Ubuntu Linux Server

object network ntp


object network plex


object network INTERNET


object-group service xbox-live-3074 tcp-udp

port-object eq 3074

object-group protocol TCPUDP

protocol-object udp

protocol-object tcp

object-group service plex-server-32400 tcp

description Plex Media Server

port-object eq 32400

access-list outside_access_in extended permit object-group TCPUDP any object xbox object-group xbox-live-3074 log alerts

access-list outside_access_in extended permit object xbox-live-88 any object xbox log alerts

access-list outside_access_in extended permit tcp any any eq echo

access-list outside_access_in remark Plex Live access

access-list outside_access_in extended permit tcp any object plex-server object-group plex-server-32400

access-list outside_access_in extended permit icmp any any time-exceeded

access-list outside_access_in extended permit icmp any any unreachable

access-list outside_access_in extended permit icmp any any echo-reply

pager lines 24

logging enable

logging asdm informational

mtu inside 1500

mtu outside 1500

mtu Guest-VLAN 1500

no failover

icmp unreachable rate-limit 1 burst-size 1

asdm image disk0:/asdm-713.bin

no asdm history enable

arp timeout 14400

no arp permit-nonconnected


object network xbox-nat-tcp3074

nat (inside,outside) static interface service tcp 3074 3074

object network xbox-nat-udp3074

nat (inside,outside) static interface service udp 3074 3074

object network xbox-nat-udp88

nat (inside,outside) static interface service udp 88 88

object network plex

nat (inside,outside) static interface service tcp 32400 32400

object network INTERNET

nat (inside,outside) dynamic interface


nat (Guest-VLAN,outside) after-auto source dynamic any interface

access-group outside_access_in in interface outside

timeout xlate 3:00:00

timeout pat-xlate 0:00:30

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

timeout floating-conn 0:00:00

dynamic-access-policy-record DfltAccessPolicy

no user-identity enable

user-identity default-domain LOCAL

aaa authentication ssh console LOCAL

aaa authentication telnet console LOCAL

http server enable

http inside

no snmp-server location

no snmp-server contact

snmp-server enable traps snmp authentication linkup linkdown coldstart warmstart

crypto ipsec security-association pmtu-aging infinite

crypto ca trustpoint _SmartCallHome_ServerCA

crl configure

crypto ca trustpoint ASDM_TrustPoint0

enrollment self

subject-name CN=border

crl configure

crypto ca trustpool policy

crypto ca certificate chain _SmartCallHome_ServerCA

certificate ca xxxx


crypto ca certificate chain ASDM_TrustPoint0

certificate xxxx


crypto ikev2 remote-access trustpoint ASDM_TrustPoint0

telnet timeout 5

ssh inside

ssh timeout 5

ssh key-exchange group dh-group1-sha1

console timeout 0

vpn-addr-assign local reuse-delay 60

dhcp-client client-id interface outside

dhcpd auto_config outside


dhcpd address inside


dhcpd address Guest-VLAN

dhcpd dns interface Guest-VLAN

dhcpd lease 86400 interface Guest-VLAN

dhcpd enable Guest-VLAN


threat-detection basic-threat

threat-detection scanning-threat shun except ip-address

threat-detection statistics

threat-detection statistics tcp-intercept rate-interval 30 burst-rate 400 average-rate 200

ntp server source outside prefer

ssl trust-point ASDM_TrustPoint0 outside

username xxx password xxx/ encrypted privilege 15


class-map inspection_default

match default-inspection-traffic



policy-map type inspect dns preset_dns_map


  message-length maximum client auto

  message-length maximum 512

policy-map global_policy

class inspection_default

  inspect icmp


service-policy global_policy global

prompt hostname context

service call-home

call-home reporting anonymous



profile CiscoTAC-1

  destination address http

  destination address email

  destination transport-method http

  subscribe-to-alert-group diagnostic

  subscribe-to-alert-group environment

  subscribe-to-alert-group inventory periodic monthly

  subscribe-to-alert-group configuration periodic monthly

  subscribe-to-alert-group telemetry periodic daily

hpm topN enable


: end

Super Bronze

ASA 5505 9.1(2) NAT/return traffic problems


Configuration seems fine.

With regards to the ICMP, you could also add this

class inspection_default

  inspect icmp error

I would probably start by trying out some other software level on the ASA

Maybe some 8.4(x) software or 9.0(x) software. See if it some bug perhaps.

One option is ofcourse to capture traffic directly on the ASA or on the hosts behind the ASA. And go through the information with Wireshark.

- Jouni

New Member

ASA 5505 9.1(2) NAT/return traffic problems

Thanks, Jouni,

I added the inspect icmp error line with no change to my NTP problem. If you have any other ideas, I'm all ears. Next up I'll try a software downgrade.

New Member

ASA 5505 9.1(2) NAT/return traffic problems

I've FINALLY found the culprit, and it was an HP 1810G switch of all things.

I was working with a Cisco engineer and we did a packet capture, and nothing was hitting the router for NTP or Xbox live. On a lark I checked out the switch settings, and the 1810G has a "Auto DoS" setting on one of the security tabs. This setting apparently kills off UDP packets, and was preventing Xbox LIve and NTP from working.

I've spent MONTHS on this crazy problem...