Deny TCP (no connection)

Asymmetric routing issue traffic is coming back a different way and the ASA doesn't like it. Check the default GW configured on the server.

See
http://www.ccierants.com/2014/06/deny-tcp-no-connection.html

characters not allowed in PSK on Cisco ASA

don't use

?
(space)
!
@

#

"

'

other vendors have their own issues with some characters had another issue on a draytek.

configure netflow on cisco router

flow record NETFLOW_RECORD
 match ipv4 tos
 match ipv4 protocol
 match ipv4 source address
 match ipv4 destination address
 match transport source-port
 match transport destination-port
 match interface input
 match flow direction
 collect interface output
 collect counter bytes long
 collect counter packets long
!
!
flow exporter NETFLOW_EXPORT_TO_SOLARWINDS
 destination x.x.x.x
 source GigabitEthernet0/0
 transport udp 2055
!
flow monitor NETFLOW_MONITOR
record NETFLOW_RECORD
exporter NETFLOW_EXPORT_TO_SOLARWINDS
cache timeout active 60
cache timeout inactive 15
!
interface gig0/1
ip flow monitor NETFLOW_MONITOR input
ip flow monitor NETFLOW_MONITOR output
!
captures all incoming traffic
route or shortest path

investigating failover on checkpoint firewall

check the tracker, you might have to open the older log file

set the origin filter to the two firewalls in question
set the filter on the message type column it has an icon for a log file or wrench etc
untick everything except control (wrench)
You can also try searching the information column for ClusterXL

on the CLI

cphaprobe state

cphaprobe -a if

enable netflow on cisco asa

https://supportforums.cisco.com/document/30476/configuring-netflow-asa-asdm

ASDM steps
Device Management > Logging > Netflow
Click Add
Fill in netflow collector server interface and port (usually 2055)

Firewall > Service Policy Rules.
Click Add
Global - applies to all interfaces
Check source and destination IP address (uses ACL)
next
source: any, user: any, destination: any, service: ip, description: netflow
next
Select flow event all, check the send box beside the ip address of the netflow collecter
Finish
Apply


CLI config
access-list global_mpc extended permit ip any any
!
flow-export destination inside 192.168.1.13 2055
!
class-map global_class
  match access-list global_mpc
!
policy-map global_policy
  class inspection_default
   inspect dns migrated_dns_map_1
     inspect ftp
     inspect h323 h225
     inspect h323 ras
     inspect netbios
     inspect rsh
     inspect rtsp
     inspect skinny
     inspect sqlnet
     inspect sunrpc
     inspect tftp
     inspect sip
     inspect xdmcp
     inspect icmp
  class global_class

flow-export event-type all destination 192.168.1.13

enable SNMP on cisco ASA

outside is the interface where the snmp server that will be checking is. In my case its coming from outside but for you it might be inside.
x.x.x.x is the IP addresses of your SNMP server

snmp-server host outside x.x.x.x community SecretCommunityString version 2c
snmp-server location Dublin
snmp-server contact admin@careface.com
snmp-server community SecretCommunityString

Wireshark

First we need to get a specific idea of the problem. Before we capture any data.

Define the problem

One app, multiple apps, everything ?
Slow or totally not working ? Any errors ?
When did the issue start ? Patches installed / updates ?
Intermittent or constant happens at peak times ?
Affects one or multiple people ?

Who, what, where, when and hopefully get to the why and resolution.

Capture close to the source of the data
If you can capture at both ends (make sure times are in sync NTP)

Problem with capturing from wireshark on the computer is that we are not seeing the data on the wire. winpcap sits in between the kernel and the NIC driver. So wireshark gets it before the NIC card. Ideally we want to see the data as it is on the wire. We can use a SPAN port for that.


Analyze - > expert info

Broadcasts storms are usually something broken, like a malfunctioning NIC and keeps firing out lots of traffic. Can be caused by no STP running and a loop has been created. Bad configuration like PIM running instead of PIM sparse mode.

Extract specific packets from a larger capture

Can mark packets with ctrl + M

Easier to use a display filter to get all packets we want (ip.addr == 192.168.1.100)

Then to file -> export specified packets

We can select the captured / displayed / marked from the radio buttons

Excessive requests and responses.

filter for arp (destination broadcast ff:ff:ff:ff:ff:ff:ff)
find the offending MAC addresses
map it to location on the network
shutdown the port or unplug the device

DNS
place the capture on the host trying to resolve DNS
Follow UDP steam

capture for tcp/udp port 53
Measure response time
expand DNS
find transaction ID
right click apply as filter selected

expand DNS
Response in: 14 (just double click it)
We will see Time: 0.04
Right click apply as a column (right click edit DNS TIME)

Capture filters
host 192.168.1.100 and host 192.168.2.200

Display filters

Find the syn packets
tcp.flags.syn == 1

Find dns packets
dns

Find dns packets with a string
dns contains "servername"

Find DNS lookups for a specific URL
dns.qry.name == "www.malware-url.com".

Find DNS queries that didn't return an answer

(!(dns.flags.rcode==0))&&(dns.flags.response==1)  

Find by string
Edit > Find Packet. Under "Find By:" select "string" and enter your search string
frame contains "string"
http contains "GET"

(http) and (frame contains "CONNECT")

(http contains CONNECT) or  (http contains GET)

Filter by IP

ip.addr==192.168.0.10

(ip.addr==192.168.0.10) or (ip.addr==192.168.0.50)

Filter by MAC

eth.addr ==xx

Show arp

arp

arp.duplicate-address-detected 

Search the payload for text

frame contains "string"

TCP len column is useful to see if the packet had data.

We need to send acks and get acks for packets we sent

TCP we don't ACK every packet we might ack every other packet.

Checking if a re-transmission is the same packet or not

IP header -> IP ID

Some retransmissions can be normal, lots usually indicate a problem like we sent request but never hear anything back so retransmit. Can indicate packet duplication (network loop) check the ip header -> ID

0.375 = 375 ms

TCP re transmission with double the number and eventually time out

1 3 6

expert info is wireshark trying to help

right click copy as a filter

coloring rules (add it)

You can add rules to your wireshark config to look out for things

setup sub interfaces on cisco ASA

This is the real interface basically it has no config

interface GigabitEthernet0/1
 speed 1000
 duplex full
 no nameif
 no security-level
 no ip address

Sub interface 20 (we use the same number as the VLAN)
interface GigabitEthernet0/1.20
 vlan 20    
 nameif LAN
 security-level 100
 ip address 10.20.1.1 255.255.255.0 standby 10.20.1.2

Sub interface 25
interface GigabitEthernet0/1.25
 vlan 25
 nameif DMZ
 security-level 50
 ip address 10.25.8.1 255.255.255.0 standby 10.25.8.2
!

Create and apply some basic ACLs
access-list LAN extended deny ip any any log
access-list LAN line 1 extended permit icmp any any log
access-group LAN in interface LAN

access-list DMZ extended deny ip any any log
access-list DMZ line 1 extended permit icmp any any log
access-group DMZ in interface DMZ

We need to attach a trunk port to Gig0/1. It must carry the VLANs 20 and 25. This config will be done on the switch.

tracing latency with wireshark

Run you capture, run your test

Open the capture, click on a packet.

right click on TCP in the bottom pane
-> protocol preferences -> calculate conversation timestamps

timestamps appears under TCP
right click -> Apply as column

sort highest number on top. Value is in seconds 1.0 is one second
0.02 is 2 ms.

FIN ACKs can be ignored as they are just closing connections

cisco asa vpn keep alives cli

sh run all | tunnel-group x.x.x.x ipsec-attributes
 ikev1 pre-shared-key *****
 peer-id-validate req
 no chain
 no ikev1 trust-point
 isakmp keepalive threshold 10 retry 2
 no ikev2 remote-authentication
 no ikev2 local-authentication


found in ASDM
Config -> Site-to-site VPN -> select peer -> Edit -> Advanced -> tunnel-group