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Step-by-Step Configuration and Troubleshooting Best Practices for the NGFW, NGIPS and AMP Technologies A Visual Guide to the Cisco Firepower Threat Defense (FTD)
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Deny IP Spoof from ( and [Scanning] drop rate.

I am replacing an outdated ISA server with a pair of asa 5515's in active / standby.  Our ISP lit up another fiber connections to us and gave us a new set of public IP's to facilitate this conversion.  I have been watching tutorials, reading forums, and googling for the last month trying to prepare for this.  Currently, I have set up access rules for one web server and a prototype direct access server.  I can access the web server over http and https without any problems by going to the non-published new public IP.

While looking at the real time logs when accessing the website, I noticed a lot of "Deny IP spoof from ( to on interface Outside" and "[Scanning] drop rate-1or2 exceeded. Current burst rate is 2 per second...".

Are these things that I should be worried about?

Thank you for any information.


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Deny IP Spoof from ( and [Scanning] drop rate.

: Saved
ASA Version 9.1(2) 
hostname WSCC-ASA1
enable password QODQ9PdmvR8vu92s encrypted
xlate per-session deny tcp any4 any4
xlate per-session deny tcp any4 any6
xlate per-session deny tcp any6 any4
xlate per-session deny tcp any6 any6
xlate per-session deny udp any4 any4 eq domain
xlate per-session deny udp any4 any6 eq domain
xlate per-session deny udp any6 any4 eq domain
xlate per-session deny udp any6 any6 eq domain
passwd 2KFQnbNIdI.2KYOU encrypted
interface GigabitEthernet0/0
 nameif Inside
 security-level 100
 ip address 
interface GigabitEthernet0/1
 description Wireless
 nameif Wireless
 security-level 75
 ip address 
interface GigabitEthernet0/2
 description Perimeter
 nameif DMZ
 security-level 50
 ip address 
interface GigabitEthernet0/3
 no nameif
 no security-level
 no ip address
interface GigabitEthernet0/4
 no nameif
 no security-level
 no ip address
interface GigabitEthernet0/5
 nameif Outside
 security-level 0
 ip address 
interface Management0/0
 nameif management
 security-level 100
 ip address 
boot system disk0:/asa912-smp-k8.bin
boot system disk0:/asa901-smp-k8.bin
ftp mode passive
clock timezone EST -5
clock summer-time EDT recurring
dns server-group DefaultDNS
same-security-traffic permit inter-interface
same-security-traffic permit intra-interface
object network OBJ_GENERIC_ALL
object network WWW_webserver
 description Cascade
object network Direct_Access
 description WSCC-S-004014
object-group network PAT-SOURCE
 description PAT Source Networks
object-group service DM_INLINE_TCP_1 tcp
 port-object eq www
 port-object eq https
access-list OUTSIDE-IN remark WSCC-S-003056
access-list OUTSIDE-IN extended permit tcp any object WWW_webserver object-group DM_INLINE_TCP_1 
access-list OUTSIDE-IN remark WSCC-S-004014
access-list OUTSIDE-IN extended permit ip any object Direct_Access 
pager lines 24
logging enable
logging asdm informational
mtu Inside 1500
mtu Wireless 1500
mtu DMZ 1500
mtu Outside 1500
mtu management 1500
no failover
icmp unreachable rate-limit 1 burst-size 1
icmp permit any Outside
asdm image disk0:/asdm-713.bin
no asdm history enable
arp timeout 14400
no arp permit-nonconnected
nat (Inside,Outside) source dynamic OBJ_GENERIC_ALL interface
object network WWW_webserver
 nat (Inside,Outside) static
object network Direct_Access
 nat (any,any) static
access-group OUTSIDE-IN in interface Outside
route Outside 1
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
user-identity default-domain LOCAL
http server enable
http management
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 trustpool policy
telnet Inside
telnet timeout 5
ssh timeout 5
ssh key-exchange group dh-group1-sha1
console timeout 0
management-access Inside
dhcpd address management
dhcpd enable management
threat-detection basic-threat
threat-detection statistics access-list
no threat-detection statistics tcp-intercept
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 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 
  inspect ip-options 
service-policy global_policy global
prompt hostname context 
no call-home reporting anonymous
: end
asdm image disk0:/asdm-713.bin
no asdm history enable

Deny IP Spoof from ( and [Scanning] drop rate.

Hello Terrence,

Well you should definetly not receiving this traffic, the ASA is doing it's job and it's denying the traffic.

Do captures and gather MAC address information for client detection:

This message is generated when a packet arrives at the security appliance interface that has a destination IP address of and a destination MAC address of the security appliance interface. In addition, this message is generated when the security appliance discarded a packet with an invalid source address, which can include one of the following or some other invalid address:

  • Loopback network (
  • Broadcast (limited, net-directed, subnet-directed, and all-subnets-directed)
  • The destination host (land.c)

In order to further enhance spoof packet detection, use the icmp command to configure the security appliance to discard packets with source addresses belonging to the internal network. This is because the access-list command has been deprecated and is no longer guaranteed to work correctly.

Recommended Action: Determine if an external user is trying to compromise the protected network. Check for misconfigured clients.

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Julio Carvajal Segura

Julio Carvajal
Senior Network Security and Core Specialist
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