Cisco ASA firewall: SQLnet inspection: buffer limit

The SQL*Net protocol consists of different packet types that the security appliance handles to make the data
stream appear consistent to the Oracle applications on either side of the security appliance.
The default port assignment for SQL*Net is 1521. This is the value used by Oracle for SQL*Net, but this
value does not agree with IANA port assignments for Structured Query Language (SQL). Use the class−map
command to apply SQL*Net inspection to a range of port numbers.
The security appliance NATs all addresses and looks in the packets for all embedded ports to open for
SQL*Net Version 1.
For SQL*Net Version 2, all DATA or REDIRECT packets that immediately follow REDIRECT packets with
a zero data length will be fixed up.
The packets that need fix−up contain embedded host/port addresses in the following format:
(ADDRESS=(PROTOCOL=tcp)(DEV=6)(HOST=a.b.c.d)(PORT=a))
SQL*Net Version 2 TNSFrame types (Connect, Accept, Refuse, Resend, and Marker) will not be scanned for
addresses to NAT nor will inspection open dynamic connections for any embedded ports in the packet.
SQL*Net Version 2 TNSFrames, Redirect, and Data packets will be scanned for ports to open and addresses
to NAT, if preceded by a REDIRECT TNSFrame type with a zero data length for the payload. When the
Redirect message with data length zero passes through the security appliance, a flag will be set in the
Re: [fw−wiz] Cisco ASA firewall: SQLnet inspection: buffer limit
Re: [fw−wiz] Cisco ASA firewall: SQLnet inspection: buffer limit 1
connection data structure to expect the Data or Redirect message that follows to be NATed and ports to be
dynamically opened. If one of the TNS frames in the preceding paragraph arrive after the Redirect message,
the flag will be reset.
The SQL*Net inspection engine will recalculate the checksum, change IP, TCP lengths, and readjust
Sequence Numbers and Acknowledgment Numbers using the delta of the length of the new and old message.
SQL*Net Version 1 is assumed for all other cases. TNSFrame types (Connect, Accept, Refuse, Resend,
Marker, Redirect, and Data) and all packets will be scanned for ports and addresses. Addresses will be
NATed and port connections will be opened.
Examples
You enable the SQL*Net inspection engine as shown in the following example, which creates a class map to
match SQL*Net traffic on the default port (1521). The service policy is then applied to the outside interface.
**Here is also where you can mark the port range [port [−port] ] − meaning you can use range 1521−2000
hostname(config)# class−map sqlnet−port
hostname(config−cmap)# match port tcp eq 1521
hostname(config−cmap)# exit
hostname(config)# policy−map sqlnet_policy
hostname(config−pmap)# class sqlnet−port
hostname(config−pmap−c)# inspect sqlnet
hostname(config−pmap−c)# exit
hostname(config)# service−policy sqlnet_policy interface outside
To enable SQL*Net inspection for all interfaces, use the global parameter in place of interface outside.

Everything got a way to exit, just only one exception, "LIFE" - How to Enlarge ARP Cache in SPLAT

The default ARP cache size in SPLAT is 1024. In cases where the number of hosts exceed 1024, you may begin to notice slow initial response times from hosts that are not frequently accessed.

Everything got a way to exit, just only one exception, "LIFE"


To enlarge the ARP cache entry table on-the-fly, run:

#sysctl -w net.ipv4.neigh.default.gc_thresh3=4096
#sysctl -w net.ipv4.neigh.default.gc_thresh2=2048
#sysctl -w net.ipv4.neigh.default.gc_thresh1=1024

To make these changes survive a reboot, modify the /etc/sysctl.conf file to include the following lines:

net.ipv4.neigh.default.gc_thresh1 = 1024
net.ipv4.neigh.default.gc_thresh2 = 2048
net.ipv4.neigh.default.gc_thresh3 = 4096

and reboot the machine.

CheckPoint Firewall-1 Commands

>fwstop
Stops the FireWall-1 daemon, management server (fwm), SNMP (snmpd)
and authentication daemon (authd).
(To stop Firewall-1 NG and load the default filter: fwstop –default, fwstop –proc)
>fwstart
Loads the FireWall-1 and starts the processes killed by fwstop.
>cpstop
Stops all Check Point applications running, except cprid.
>cpstart
Starts all Check Point applications.
>cpconfig
In NT, opens Check Point Configuration Tool GUI. (licenses, admins …)
>cpstat options
Provides status of the target hosts.
Usage: cpstat [-h host][-p port][-f flavour][-o polling [-c count] [-e period]]
[-d] application_flag
-h A resolvable hostname, a dot-notation address, or a DAIP object name.
Default is localhost.
-p Port number of the AMON server.
Default is the standard AMON port (18192).
-f The flavour of the output (as appears in the configuration file).
Default is to use the first flavour found in the configuration file.
-o Polling interval (seconds) specifies the pace of the results.
Default is 0, meaning the results are shown only once.
-c Specifying how many times the results are shown.
Default is 0, meaning the results are repeatedly shown.
-e Period interval (seconds) specifies the interval over which "statistical" oids are computed.
Ignored for regular oids.
-d Debug mode
Available application_flags:
Flag Flavours
--------------------------------------------------------------------------------------------------
fw default, policy, perf, hmem, kmem, inspect, cookies, chains, fragments, totals,
ufp, http, ftp, telnet, rlogin, smtp, sync, all
--------------------------------------------------------------------------------------------------
ha default, all
--------------------------------------------------------------------------------------------------
ls default
--------------------------------------------------------------------------------------------------
mg default
--------------------------------------------------------------------------------------------------
os default, routing, memory, old_memory, cpu, disk, perf, all, average_cpu,
average_memory, statistics
--------------------------------------------------------------------------------------------------
persistency product, TableConfig, SourceConfig
--------------------------------------------------------------------------------------------------
polsrv default, all
--------------------------------------------------------------------------------------------------
vpn default, product, IKE, ipsec, traffic, compression, accelerator, nic, statistics,
watermarks, all
--------------------------------------------------------------------------------------------------
FireWall-1 Commands
>fw ver [-h] ..
Display version
This is Check Point VPN-1(TM) & FireWall-1(R) NG Feature Pack 3 Build 53920
>fw kill [-sig_no] procname
Send signal to a daemon
>fw putkey –n ip_address_host ip_address_of_closest_interface
Client server keys; helpful if you are integrating an NG Management Server
with 4.x enforcement modules. Will install an authenticating password; used
to authenticate SIC between the Management Server and the module.
>fw sam (Suspicious Activities Monitoring)
Usage:
sam [-v] [-s sam-server] [-S server-sic-name] [-t timeout] [-l log] [-f fw-host]
[-C] -((n|i|I|j|J)
sam [-v] [-s sam-server] [-S server-sic-name] [-f fw-host] -M -ijn
sam [-v] [-s sam-server] [-S server-sic-name] [-f fw-host] -D
Criteria may be one of:
src
dst
any
subsrc
subdst
subany
srv
subsrv
subsrvs
subsrvd
dstsrv
subdstsrv
srcpr
dstpr
subsrcpr
subdstpr
>fw fetch ip_address_management_station
Used to fetch Inspection code from a specified host and install it to the
kernel of the current host.
>fw tab [-h] ...
Displays the contents of FireWall-1’s various tables
>fw tab –t connections –s tells how many connections in state table
>fw monitor [-h] ...
Monitor VPN-1/FW-1 traffic
>fw ctl [args] install, uninstall, pstat, iflist, arp, debug, kdebug, chain, conn
Control kernel
>fw ctl pstat shows the internal statistics – memory/connections
>fw ctl arp shows firewall’s ARP cache – IP addresses via NAT
>fw lichosts
Display protected hosts
>fw log [-h] ...
Display logs
>fw logswitch [-h target] [+|-][oldlog]
Create a new log file; the old log is moved
>fw repairlog ...
Log index recreation
>fw mergefiles ...
log files merger
>fw lslogs ...
Remote machine log file list
>fw fetchlogs ...
Fetch logs from a remote host
FireWall Management Server Commands
>fwm ver [-h] ...
Display version
>fwm load [opts] [filter-file|rule-base] targets
Will convert the *.W file from the GUI to a *.pf file and compile into
Inspection code, installing a Security Policy on an enforcement module.
>fwm load Standard.W all.all@localgateway
>fwm unload [opts] targets
Uninstall Security Policy from the specified target(s).
>fwm dbload [targets]
Download the database
>fwm logexport [-h] ...
Export log to ascii file
>fwm logexport [-d delimiter] [-i filename] [-o filename] [-n] [-f] [-m
] [-a]
Where:
-d - Set the output delimiter. Default is ;
-i - Input file name. Default is the active log file, fw.log
-o - Output file name. Default is printing to the screen
-n - No IP resolving. Default is to resolve all IPs
-f - In case of active file (fw.log), wait for new records and export them
-m - Unification mode. Default is initial order.
Initial - initial order mode
Raw - No unification
Semi - Semi-unified mode
-a - Take account records only. Default is export all records
Once your logs files have been written to a backup file you can begin to export them into an
ASCII format so you may begin to analyze them. The command that accomplishes this is
the fw logexport command. The format of this command is as follows:
C:\WINNT\FW1\NG\log>fwm logexport -d , -i 2003-03-19_235900_1.log -o fwlog2003-03-
19.txt
The –d switch specifies a delimiter character with the default being the semi-colon.
The –i switch specifies the input file and the –o switch specifies the output file. The –n
switch tells the program to not perform any name resolution on the IP addresses. This will
greatly speed up the export process. If you have the time and want to see the domain
names instead of IP addresses you may omit this switch. One word of caution though, the
size of the output files that get created grow an average of 2.5 times the input file.
>fwm gen [-RouterType [-import]] rule-base
Generate an inspection script or a router access-list
>fwm dbexport [-h] ...
Export the database
>fwm ikecrypt
Crypt a secret with a key (for the dbexport command)
>fwm dbimport [-h] ...
Import to database
SmartUpdate commands – Requires license
>cppkg add
>cppkg del [vendor] [product] [version] [os] [sp]
>cppkg print
>cppkg setroot
>cppkg getroot

monitoring vpn tunnels

The solution find this one is becoz of in my previous organisation We have N number of tunnels as checkpoint is being used enterprise wide. as of now there is no monitoring mechanism for vpn tunnel been established. whenever tunnel goes down, we come to know only if project team complains. So i though Is there any mechanism to monitor vpn tunnels.

Here is few ways

1)

You could use:

Code:

cpstat vpn -f ipsec

to check the number of inbound and outbound SAs.

2)

If you are using Check Point gateways on both sides of the VPN, the best way to do this is to set Permanent Tunnels in the VPN Community. On the "Tunnel Management" screen of the VPN community you can set up automatic Emails/SNMP Traps for when the tunnel falls down and can't get back up. Once again permanent tunnels only works between Check Point gateways.

If the remote firewalls are not Check Point, the best you can do under "Global Properties...Log and Alert" is to set "VPN Configuration & Key Exchange Errors" & "VPN Packet Handling Errors" to an Email/SNMP Trap to notify you if a tunnel fails. These log events should not trip unless there is a problem, just be sure to temporarily disable these when setting up & testing a new VPN or you will get bombed with alerts. :-)

Clear ARP Cache - SPLAT

here is an alternative by using the fabulous ip utility.
(Only supported on SecurePlatform/Linux)

Flush all arp enties on interface eth0:

Code:

# ip neigh flush dev eth0

Flush arp entry for host 10.20.30.40:

Code:

# ip neigh flush 10.20.30.40

Flush arp entry for all hosts in network 192.168.0.0/24:

Code:

# ip neigh flush 192.168.0.0/24

Flush all arp entries:

Code:

# ip neigh flush all

For verbose output use:

Code:

# ip -s -s neigh flush ...

Comments are invited if any other easy way

Every Small Things Have Its OWN Significance : Nokia Backip thru CLISH

I think now a days am becoming lazy... Two days back I got a call from one of my colleague, he want to back up Nokia, ofcoz Answer was as simple as that.. Goto Voyager=>backup.. But not all the time... he don't have any access to voyager, and its a Severity 1 Call..

I thought of CLISH.. the command line of Nokia, which I skipped during my studies thinking that Voyager Gonna Help me for all..

Yes.. I found that Clish Can Do That..

BACKUP USING CLISH
==================

1.clish -c "set backup manual filename ipso-backup"

2.clish -c "set backup manual on"

3. check the back created in /var/backup/

BACKUP RESTORE
==============

To restore run the following command :
view sourceprint?1.clish -c "set restore manual /[path]/[filename].tgz


Moral Story
===========

Dont Leave anything thinking that better is available.. When you are in trouble small things gonna play the role.... Enuf for 2DAY..

TCPDUMP

NAME

tcpdump - dump traffic on a network

SYNOPSIS

tcpdump [ -AdDefIKlLnNOpqRStuUvxX ] [ -B buffer_size ] [ -c count ]

[ -C file_size ] [ -G rotate_seconds ] [ -F file ]

[ -i interface ] [ -m module ] [ -M secret ]

[ -r file ] [ -s snaplen ] [ -T type ] [ -w file ]

[ -W filecount ]

[ -E spi@ipaddr algo:secret,... ]

[ -y datalinktype ] [ -z postrotate-command ] [ -Z user ]
[ expression ]

DESCRIPTION

Tcpdump prints out a description of the contents of packets on a network interface that match the boolean expression. It can also be run with the -w flag, which causes it to save the packet data to a file for later analysis, and/or with the -r flag, which causes it to read from a saved packet file rather than to read packets from a network interface. In all cases, only packets that match expression will be processed by tcpdump.

Tcpdump will, if not run with the -c flag, continue capturing packets until it is interrupted by a SIGINT signal (generated, for example, by typing your interrupt character, typically control-C) or a SIGTERM signal (typically generated with the kill(1) command); if run with the -c flag, it will capture packets until it is interrupted by a SIGINT or SIGTERM signal or the specified number of packets have been processed.

When tcpdump finishes capturing packets, it will report counts of:

packets ``captured'' (this is the number of packets that tcpdump has received and processed);

packets ``received by filter'' (the meaning of this depends on the OS on which you're running tcpdump, and possibly on the way the OS was configured - if a filter was specified on the command line, on some OSes it counts packets regardless of whether they were matched by the filter expression and, even if they were matched by the filter expression, regardless of whether tcpdump has read and processed them yet, on other OSes it counts only packets that were matched by the filter expression regardless of whether tcpdump has read and processed them yet, and on other OSes it counts only packets that were matched by the filter expression and were processed by tcpdump);

packets ``dropped by kernel'' (this is the number of packets that were dropped, due to a lack of buffer space, by the packet capture mechanism in the OS on which tcpdump is running, if the OS reports that information to applications; if not, it will be reported as 0).

On platforms that support the SIGINFO signal, such as most BSDs (including Mac OS X) and Digital/Tru64 UNIX, it will report those counts when it receives a SIGINFO signal (generated, for example, by typing your ``status'' character, typically control-T, although on some platforms, such as Mac OS X, the ``status'' character is not set by default, so you must set it with stty(1) in order to use it) and will continue capturing packets.

Reading packets from a network interface may require that you have special privileges; see the pcap (3PCAP) man page for details. Reading a saved packet file doesn't require special privileges.

OPTIONS

-A

Print each packet (minus its link level header) in ASCII. Handy for capturing web pages.

-B

Set the operating system capture buffer size to buffer_size.

-c

Exit after receiving count packets.

-C

Before writing a raw packet to a savefile, check whether the file is currently larger than file_size and, if so, close the current savefile and open a new one. Savefiles after the first savefile will have the name specified with the -w flag, with a number after it, starting at 1 and continuing upward. The units of file_size are millions of bytes (1,000,000 bytes, not 1,048,576 bytes).

-d

Dump the compiled packet-matching code in a human readable form to standard output and stop.

-dd

Dump packet-matching code as a C program fragment.

-ddd

Dump packet-matching code as decimal numbers (preceded with a count).

-D

Print the list of the network interfaces available on the system and on which tcpdump can capture packets. For each network interface, a number and an interface name, possibly followed by a text description of the interface, is printed. The interface name or the number can be supplied to the -i flag to specify an interface on which to capture.

This can be useful on systems that don't have a command to list them (e.g., Windows systems, or UNIX systems lacking ifconfig -a); the number can be useful on Windows 2000 and later systems, where the interface name is a somewhat complex string.

The -D flag will not be supported if tcpdump was built with an older version of libpcap that lacks the pcap_findalldevs() function.

-e

Print the link-level header on each dump line.

-E

Use spi@ipaddr algo:secret for decrypting IPsec ESP packets that are addressed to addr and contain Security Parameter Index value spi. This combination may be repeated with comma or newline seperation.

Note that setting the secret for IPv4 ESP packets is supported at this time.

Algorithms may be des-cbc, 3des-cbc, blowfish-cbc, rc3-cbc, cast128-cbc, or none. The default is des-cbc. The ability to decrypt packets is only present if tcpdump was compiled with cryptography enabled.

secret is the ASCII text for ESP secret key. If preceeded by 0x, then a hex value will be read.

The option assumes RFC2406 ESP, not RFC1827 ESP. The option is only for debugging purposes, and the use of this option with a true `secret' key is discouraged. By presenting IPsec secret key onto command line you make it visible to others, via ps(1) and other occasions.

In addition to the above syntax, the syntax file name may be used to have tcpdump read the provided file in. The file is opened upon receiving the first ESP packet, so any special permissions that tcpdump may have been given should already have been given up.

-f

Print `foreign' IPv4 addresses numerically rather than symbolically (this option is intended to get around serious brain damage in Sun's NIS server --- usually it hangs forever translating non-local internet numbers).

The test for `foreign' IPv4 addresses is done using the IPv4 address and netmask of the interface on which capture is being done. If that address or netmask are not available, available, either because the interface on which capture is being done has no address or netmask or because the capture is being done on the Linux "any" interface, which can capture on more than one interface, this option will not work correctly.

-F

Use file as input for the filter expression. An additional expression given on the command line is ignored.

-G

If specified, rotates the dump file specified with the -w option every rotate_seconds seconds. Savefiles will have the name specified by -w which should include a time format as defined by strftime(3). If no time format is specified, each new file will overwrite the previous.

If used in conjunction with the -C option, filenames will take the form of `file'.

-i

Listen on interface. If unspecified, tcpdump searches the system interface list for the lowest numbered, configured up interface (excluding loopback). Ties are broken by choosing the earliest match.

On Linux systems with 2.2 or later kernels, an interface argument of ``any'' can be used to capture packets from all interfaces. Note that captures on the ``any'' device will not be done in promiscuous mode.

If the -D flag is supported, an interface number as printed by that flag can be used as the interface argument.

-I

Put the interface in "monitor mode"; this is supported only on IEEE 802.11 Wi-Fi interfaces, and supported only on some operating systems.

Note that in monitor mode the adapter might disassociate from the network with which it's associated, so that you will not be able to use any wireless networks with that adapter. This could prevent accessing files on a network server, or resolving host names or network addresses, if you are capturing in monitor mode and are not connected to another network with another adapter.

This flag will affect the output of the -L flag. If -I isn't specified, only those link-layer types available when not in monitor mode will be shown; if -I is specified, only those link-layer types available when in monitor mode will be shown.

-K

Don't attempt to verify IP, TCP, or UDP checksums. This is useful for interfaces that perform some or all of those checksum calculation in hardware; otherwise, all outgoing TCP checksums will be flagged as bad.

-l

Make stdout line buffered. Useful if you want to see the data while capturing it. E.g.,
``tcpdump -l | tee dat'' or ``tcpdump -l > dat & tail -f dat''.

-L

List the known data link types for the interface, in the specified mode, and exit. The list of known data link types may be dependent on the specified mode; for example, on some platforms, a Wi-Fi interface might support one set of data link types when not in monitor mode (for example, it might support only fake Ethernet headers, or might support 802.11 headers but not support 802.11 headers with radio information) and another set of data link types when in monitor mode (for example, it might support 802.11 headers, or 802.11 headers with radio information, only in monitor mode).

-m

Load SMI MIB module definitions from file module. This option can be used several times to load several MIB modules into tcpdump.

-M

Use secret as a shared secret for validating the digests found in TCP segments with the TCP-MD5 option (RFC 2385), if present.

-n

Don't convert addresses (i.e., host addresses, port numbers, etc.) to names.

-N

Don't print domain name qualification of host names. E.g., if you give this flag then tcpdump will print ``nic'' instead of ``nic.ddn.mil''.

-O

Do not run the packet-matching code optimizer. This is useful only if you suspect a bug in the optimizer.

-p

Don't put the interface into promiscuous mode. Note that the interface might be in promiscuous mode for some other reason; hence, `-p' cannot be used as an abbreviation for `ether host {local-hw-addr} or ether broadcast'.

-q

Quick (quiet?) output. Print less protocol information so output lines are shorter.

-R

Assume ESP/AH packets to be based on old specification (RFC1825 to RFC1829). If specified, tcpdump will not print replay prevention field. Since there is no protocol version field in ESP/AH specification, tcpdump cannot deduce the version of ESP/AH protocol.

-r

Read packets from file (which was created with the -w option). Standard input is used if file is ``-''.

-S

Print absolute, rather than relative, TCP sequence numbers.

-s

Snarf snaplen bytes of data from each packet rather than the default of 65535 bytes. Packets truncated because of a limited snapshot are indicated in the output with ``[|proto]'', where proto is the name of the protocol level at which the truncation has occurred. Note that taking larger snapshots both increases the amount of time it takes to process packets and, effectively, decreases the amount of packet buffering. This may cause packets to be lost. You should limit snaplen to the smallest number that will capture the protocol information you're interested in. Setting snaplen to 0 sets it to the default of 65535, for backwards compatibility with recent older versions of tcpdump.

-T

Force packets selected by "expression" to be interpreted the specified type. Currently known types are aodv (Ad-hoc On-demand Distance Vector protocol), cnfp (Cisco NetFlow protocol), rpc(Remote Procedure Call), rtp (Real-Time Applications protocol), rtcp (Real-Time Applications control protocol), snmp (Simple Network Management Protocol), tftp (Trivial File Transfer Protocol),vat (Visual Audio Tool), and wb (distributed White Board).

-t

Don't print a timestamp on each dump line.

-tt

Print an unformatted timestamp on each dump line.

-ttt

Print a delta (micro-second resolution) between current and previous line on each dump line.

-tttt

Print a timestamp in default format proceeded by date on each dump line.

-ttttt

Print a delta (micro-second resolution) between current and first line on each dump line.

-u

Print undecoded NFS handles.

-U

Make output saved via the -w option ``packet-buffered''; i.e., as each packet is saved, it will be written to the output file, rather than being written only when the output buffer fills.

The -U flag will not be supported if tcpdump was built with an older version of libpcap that lacks the pcap_dump_flush() function.

-v

When parsing and printing, produce (slightly more) verbose output. For example, the time to live, identification, total length and options in an IP packet are printed. Also enables additional packet integrity checks such as verifying the IP and ICMP header checksum.

When writing to a file with the -w option, report, every 10 seconds, the number of packets captured.

-vv

Even more verbose output. For example, additional fields are printed from NFS reply packets, and SMB packets are fully decoded.

-vvv

Even more verbose output. For example, telnet SB ... SE options are printed in full. With -X Telnet options are printed in hex as well.

-w

Write the raw packets to file rather than parsing and printing them out. They can later be printed with the -r option. Standard output is used if file is ``-''. See pcap-savefile(5) for a description of the file format.

-W

Used in conjunction with the -C option, this will limit the number of files created to the specified number, and begin overwriting files from the beginning, thus creating a 'rotating' buffer. In addition, it will name the files with enough leading 0s to support the maximum number of files, allowing them to sort correctly.

Used in conjunction with the -G option, this will limit the number of rotated dump files that get created, exiting with status 0 when reaching the limit. If used with -C as well, the behavior will result in cyclical files per timeslice.

-x

When parsing and printing, in addition to printing the headers of each packet, print the data of each packet (minus its link level header) in hex. The smaller of the entire packet or snaplen bytes will be printed. Note that this is the entire link-layer packet, so for link layers that pad (e.g. Ethernet), the padding bytes will also be printed when the higher layer packet is shorter than the required padding.

-xx

When parsing and printing, in addition to printing the headers of each packet, print the data of each packet, including its link level header, in hex.

-X

When parsing and printing, in addition to printing the headers of each packet, print the data of each packet (minus its link level header) in hex and ASCII. This is very handy for analysing new protocols.

-XX

When parsing and printing, in addition to printing the headers of each packet, print the data of each packet, including its link level header, in hex and ASCII.

-y

Set the data link type to use while capturing packets to datalinktype.

-z

Used in conjunction with the -C or -G options, this will make tcpdump run " command file " where file is the savefile being closed after each rotation. For example, specifying -z gzip or -z bzip2 will compress each savefile using gzip or bzip2.

Note that tcpdump will run the command in parallel to the capture, using the lowest priority so that this doesn't disturb the capture process.

And in case you would like to use a command that itself takes flags or different arguments, you can always write a shell script that will take the savefile name as the only argument, make the flags & arguments arrangements and execute the command that you want.

-Z

Drops privileges (if root) and changes user ID to user and the group ID to the primary group of user.

This behavior can also be enabled by default at compile time.

expression

selects which packets will be dumped. If no expression is given, all packets on the net will be dumped. Otherwise, only packets for which expression is `true' will be dumped.

For the expression syntax, see pcap-filter(7).

Expression arguments can be passed to tcpdump as either a single argument or as multiple arguments, whichever is more convenient. Generally, if the expression contains Shell metacharacters, it is easier to pass it as a single, quoted argument. Multiple arguments are concatenated with spaces before being parsed.

EXAMPLES

To print all packets arriving at or departing from sundown:

tcpdump host sundown 

To print traffic between helios and either hot or ace:

tcpdump host helios and \( hot or ace \) 

To print all IP packets between ace and any host except helios:

tcpdump ip host ace and not helios 

To print all traffic between local hosts and hosts at Berkeley:

tcpdump net ucb-ether 

To print all ftp traffic through internet gateway snup: (note that the expression is quoted to prevent the shell from (mis-)interpreting the parentheses):

tcpdump 'gateway snup and (port ftp or ftp-data)' 

To print traffic neither sourced from nor destined for local hosts (if you gateway to one other net, this stuff should never make it onto your local net).

tcpdump ip and not net localnet 

To print the start and end packets (the SYN and FIN packets) of each TCP conversation that involves a non-local host.

tcpdump 'tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet' 

To print all IPv4 HTTP packets to and from port 80, i.e. print only packets that contain data, not, for example, SYN and FIN packets and ACK-only packets. (IPv6 is left as an exercise for the reader.)

tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2))>>2)) != 0)' 

To print IP packets longer than 576 bytes sent through gateway snup:

tcpdump 'gateway snup and ip[2:2] > 576' 

To print IP broadcast or multicast packets that were not sent via Ethernet broadcast or multicast:

tcpdump 'ether[0] & 1 = 0 and ip[16] >= 224' 

To print all ICMP packets that are not echo requests/replies (i.e., not ping packets):

tcpdump 'icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply' 

OUTPUT FORMAT

The output of tcpdump is protocol dependent. The following gives a brief description and examples of most of the formats.

Link Level Headers

If the '-e' option is given, the link level header is printed out. On Ethernets, the source and destination addresses, protocol, and packet length are printed.

On FDDI networks, the '-e' option causes tcpdump to print the `frame control' field, the source and destination addresses, and the packet length. (The `frame control' field governs the interpretation of the rest of the packet. Normal packets (such as those containing IP datagrams) are `async' packets, with a priority value between 0 and 7; for example, `async4'. Such packets are assumed to contain an 802.2 Logical Link Control (LLC) packet; the LLC header is printed if it is not an ISO datagram or a so-called SNAP packet.

On Token Ring networks, the '-e' option causes tcpdump to print the `access control' and `frame control' fields, the source and destination addresses, and the packet length. As on FDDI networks, packets are assumed to contain an LLC packet. Regardless of whether the '-e' option is specified or not, the source routing information is printed for source-routed packets.

On 802.11 networks, the '-e' option causes tcpdump to print the `frame control' fields, all of the addresses in the 802.11 header, and the packet length. As on FDDI networks, packets are assumed to contain an LLC packet.

(N.B.: The following description assumes familiarity with the SLIP compression algorithm described in RFC-1144.)

On SLIP links, a direction indicator (``I'' for inbound, ``O'' for outbound), packet type, and compression information are printed out. The packet type is printed first. The three types are ip, utcp, and ctcp. No further link information is printed for ip packets. For TCP packets, the connection identifier is printed following the type. If the packet is compressed, its encoded header is printed out. The special cases are printed out as *S+n and *SA+n, where n is the amount by which the sequence number (or sequence number and ack) has changed. If it is not a special case, zero or more changes are printed. A change is indicated by U (urgent pointer), W (window), A (ack), S (sequence number), and I (packet ID), followed by a delta (+n or -n), or a new value (=n). Finally, the amount of data in the packet and compressed header length are printed.

For example, the following line shows an outbound compressed TCP packet, with an implicit connection identifier; the ack has changed by 6, the sequence number by 49, and the packet ID by 6; there are 3 bytes of data and 6 bytes of compressed header:

O ctcp * A+6 S+49 I+6 3 (6) 

ARP/RARP Packets

Arp/rarp output shows the type of request and its arguments. The format is intended to be self explanatory. Here is a short sample taken from the start of an `rlogin' from host rtsg to host csam:

arp who-has csam tell rtsg arp reply csam is-at CSAM  

The first line says that rtsg sent an arp packet asking for the Ethernet address of internet host csam. Csam replies with its Ethernet address (in this example, Ethernet addresses are in caps and internet addresses in lower case).

This would look less redundant if we had done tcpdump -n:

arp who-has 128.3.254.6 tell 128.3.254.68 arp reply 128.3.254.6 is-at 02:07:01:00:01:c4 

If we had done tcpdump -e, the fact that the first packet is broadcast and the second is point-to-point would be visible:

RTSG Broadcast 0806  64: arp who-has csam tell rtsg CSAM RTSG 0806  64: arp reply csam is-at CSAM  

For the first packet this says the Ethernet source address is RTSG, the destination is the Ethernet broadcast address, the type field contained hex 0806 (type ETHER_ARP) and the total length was 64 bytes.

TCP Packets

(N.B.:The following description assumes familiarity with the TCP protocol described in RFC-793. If you are not familiar with the protocol, neither this description nor tcpdump will be of much use to you.)

The general format of a tcp protocol line is:

src > dst: flags data-seqno ack window urgent options  

Src and dst are the source and destination IP addresses and ports. Flags are some combination of S (SYN), F (FIN), P (PUSH), R (RST), W (ECN CWR) or E (ECN-Echo), or a single `.' (no flags).Data-seqno describes the portion of sequence space covered by the data in this packet (see example below). Ack is sequence number of the next data expected the other direction on this connection.Window is the number of bytes of receive buffer space available the other direction on this connection. Urg indicates there is `urgent' data in the packet. Options are tcp options enclosed in angle brackets (e.g., ).

Src, dst and flags are always present. The other fields depend on the contents of the packet's tcp protocol header and are output only if appropriate.

Here is the opening portion of an rlogin from host rtsg to host csam.

rtsg.1023 > csam.login: S 768512:768512(0) win 4096  csam.login > rtsg.1023: S 947648:947648(0) ack 768513 win 4096  rtsg.1023 > csam.login: . ack 1 win 4096 rtsg.1023 > csam.login: P 1:2(1) ack 1 win 4096 csam.login > rtsg.1023: . ack 2 win 4096 rtsg.1023 > csam.login: P 2:21(19) ack 1 win 4096 csam.login > rtsg.1023: P 1:2(1) ack 21 win 4077 csam.login > rtsg.1023: P 2:3(1) ack 21 win 4077 urg 1 csam.login > rtsg.1023: P 3:4(1) ack 21 win 4077 urg 1  

The first line says that tcp port 1023 on rtsg sent a packet to port login on csam. The S indicates that the SYN flag was set. The packet sequence number was 768512 and it contained no data. (The notation is `first:last(nbytes)' which means `sequence numbers first up to but not including last which is nbytes bytes of user data'.) There was no piggy-backed ack, the available receive window was 4096 bytes and there was a max-segment-size option requesting an mss of 1024 bytes.

Csam replies with a similar packet except it includes a piggy-backed ack for rtsg's SYN. Rtsg then acks csam's SYN. The `.' means no flags were set. The packet contained no data so there is no data sequence number. Note that the ack sequence number is a small integer (1). The first time tcpdump sees a tcp `conversation', it prints the sequence number from the packet. On subsequent packets of the conversation, the difference between the current packet's sequence number and this initial sequence number is printed. This means that sequence numbers after the first can be interpreted as relative byte positions in the conversation's data stream (with the first data byte each direction being `1'). `-S' will override this feature, causing the original sequence numbers to be output.

On the 6th line, rtsg sends csam 19 bytes of data (bytes 2 through 20 in the rtsg -> csam side of the conversation). The PUSH flag is set in the packet. On the 7th line, csam says it's received data sent by rtsg up to but not including byte 21. Most of this data is apparently sitting in the socket buffer since csam's receive window has gotten 19 bytes smaller. Csam also sends one byte of data to rtsg in this packet. On the 8th and 9th lines, csam sends two bytes of urgent, pushed data to rtsg.

If the snapshot was small enough that tcpdump didn't capture the full TCP header, it interprets as much of the header as it can and then reports ``[|tcp]'' to indicate the remainder could not be interpreted. If the header contains a bogus option (one with a length that's either too small or beyond the end of the header), tcpdump reports it as ``[bad opt]'' and does not interpret any further options (since it's impossible to tell where they start). If the header length indicates options are present but the IP datagram length is not long enough for the options to actually be there, tcpdump reports it as ``[bad hdr length]''.

Capturing TCP packets with particular flag combinations (SYN-ACK, URG-ACK, etc.)

There are 8 bits in the control bits section of the TCP header:

CWR | ECE | URG | ACK | PSH | RST | SYN | FIN

Let's assume that we want to watch packets used in establishing a TCP connection. Recall that TCP uses a 3-way handshake protocol when it initializes a new connection; the connection sequence with regard to the TCP control bits is

1) Caller sends SYN

2) Recipient responds with SYN, ACK

3) Caller sends ACK

Change IP address on the interface without losing the connection

I happen from time to time to configure from scratch some Checkpoint UTM/Open Server that is thousand miles away. And from experience the best way to do it is when you have out-of-band fast access to the firewall. Of course not always such well-organized beforehand set up is available. Just like today when I was asked how to change IP address on the interfcae through which you are connected to the firewall.
Ok, to be more specific – client had been connected with his UTM through some ISP that included also IP addresses on the WAN (External) interface of the firewall. Time has come to change ISP and accordingly its IP addresses.
All went surprisingly well, my collegue added new IP address on the External interface as the Secondary IP and from then on he could access/manage firewall through this new IP without a hitch. There is one but though – SSL VPN service was still listening on the old IP and didn’t work because of that. So we had to remove the new IP as Secondary and put it as the Primary one. For this he asked my opinion , I set up some improvised lab and here is how to do it .

1) First, for unmanned location I set up in cron to do restart in say 10-15 minutes from now so if something goes wrong restart will discard any changes done in step 2;

[Expert@R71]# crontab -l
# DO NOT EDIT THIS FILE – edit the master and reinstall.
# (/tmp/crontab.5649 installed on Wed Jun 2 11:25:53 2010)
# (Cron version — $Id: crontab.c,v 2.13 1994/01/17 03:20:37 vixie Exp $)
27 11 * * * /sbin/reboot

2) Connected through the ssh I did the following two commands on the same line that when finished should not even disconnect you from the ssh. It brings down secondary IP (aliased interface) and assigns this IP to the External interface as the usual Primary one.

ifconfig External:0 down ; ifconfig External 192.168.2.22 netmask 255.255.255.0

Troubleshooting VSX

1. Perform a basic configuration check for each gateway/cluster member by
running:
fw vsx stat -v
From this you will:
a. account for all Virtual Systems (that none are missing from the
configuration)
b. see all Virtual Systems are active
c. see all Virtual Systems have a correct security policy
d. see if you have sufficient licenses.
2. Perform a check on the status for each gateway/cluster member by running:
cphaprob state
3. If you suspect a Virtual System has connectivity problems:
a. Run: fw vsx set to set the context to a specific Virtual System.
b. Run fw getifs [-vs vsname or vsid] to get the interface list for the
specific Virtual System.
c. Examine connectivity status using standard Operating System commands
and tools such as: ping, traceroute, tcpdump, telnet, ip route, ftp, etc.
Some of these are run according to context (that is routing, source and
destination IP Addresses). In addition system-specific checks can be made
on the network.
For Linux/SecurePlatform, run:
ip route and ip link
If these tests indicate that all interfaces and routers have connectivity, and
appear to be functioning correctly, you should monitor the passage of
packets through the system.

4. Run fw monitor -vs [vsname or vsid] to capture details of packets at
multiple points. This may return multiple reports on the same packet as it
passes various capture points. This will not report on Virtual Routers, except for
packets destined to the External Virtual Router.