Convert Cisco dumps into Wireshark's pcap format

Lately i've been experimenting a lot with the hidden "dump" option of "debug ip packet", trying to decode various protocols. Yesterday i wrote a post about decoding the tacacs communication, something that required a little bit of awkward text editing.

Tonight i created the following perl program in order to make the whole process easier.

#!/opt/perl/bin/perl

# ciscodump2text v0.1
#
# Convert Cisco hex dump format (captured through the "debug ip packet dump" command)
# to a special text format that can then be fed into text2pcap 
# so a pcap file for Wireshark can be created at the end
#
# Copyright (C) 2009 Tassos (http://ccie-in-3-months.blogspot.com)
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

@packets = ();
$junk_line = 1;
$i = 0;

while (<>) {
        $line = $_;

        if ( $line =~ /^[0-9A-F]{8}: / ) {

                $hex_part = substr($line, 10, 36);
                $hex_part =~ s/\s//g;

                if ( $junk_line ) {
                        $i++;
                        $packets[$i] = "";
                        $junk_line = 0;
                };

                $packets[$i] .= $hex_part;
        } else {
                $junk_line = 1;
        }
}

for ($i = 1; $i <= @packets; $i++) {

        if ( exists $packets[$i] ) {

                for ( $j = 0; $j < length($packets[$i]); $j += 2 ) {
                        if ( $j == 0 )  {
                                printf "# Packet $i\n%08X", $j/2;
                        } elsif ( $j % 32 == 0 ) {
                                printf " #\n%08X", $j/2;
                        }
                        print " ".substr($packets[$i], $j, 2);
                }

                print " #\n";
        }
}

print "\n";

You just give it the cisco dump as input (only lines starting with an 8-char hex number are processed, so you don't have to worry about other lines) and it produces a text file that can be fed into text2pcap. Then you give text2pcap the new text file as input and it produces a pcap file as output, which can be opened with Wireshark.

i.e. we want to convert the following log produced by "debug ip packet dump" to a text file compatible with the "text2pcap" program.

*Apr 18 18:19:51.887: FIBipv4-packet-proc: route packet from (local) src 10.10.10.9 dst 10.10.10.10
*Apr 18 18:19:51.887: FIBipv4-packet-proc: packet routing succeeded
*Apr 18 18:19:51.887: IP: s=10.10.10.9 (local), d=10.10.10.10 (FastEthernet0/1), len 80, sending
*Apr 18 18:19:51.887:     TCP src=20596, dst=49, seq=1187787226, ack=3815757335, win=4128 ACK
082D17D0:                   45000050 678B0000          E..Pg...
082D17E0: FF062BF6 0A0A0A09 0A0A0A0A 50740031  ..+v........Pt.1
082D17F0: 46CC31DA E36FD617 50101020 9F960000  FL1ZcoV.P.. ....
082D1800: C0010100 99648E6A 0000001C B8145EC8  @....d.j....8.^H
082D1810: A8B3C2B9 3EC12A1F AA40DE66 D7429C89  (3B9>A*.*@^fWB..
082D1820: 0BF911F3 C7249F5F                    .y.sG$._
*Apr 18 18:19:51.887: IP: s=10.10.10.9 (local), d=10.10.10.10 (FastEthernet0/1), len 80, sending full packet
*Apr 18 18:19:51.887:     TCP src=20596, dst=49, seq=1187787226, ack=3815757335, win=4128 ACK
082D17C0:                       0200 4C4F4F50            ..LOOP
082D17D0: CA000CB8 00060800 45000050 678B0000  J..8....E..Pg...
082D17E0: FF062BF6 0A0A0A09 0A0A0A0A 50740031  ..+v........Pt.1
082D17F0: 46CC31DA E36FD617 50101020 9F960000  FL1ZcoV.P.. ....
082D1800: C0010100 99648E6A 0000001C B8145EC8  @....d.j....8.^H
082D1810: A8B3C2B9 3EC12A1F AA40DE66 D7429C89  (3B9>A*.*@^fWB..
082D1820: 0BF911F3 C7249F5F                    .y.sG$._
*Apr 18 18:19:52.103: FIBipv4-packet-proc: route packet from (local) src 10.10.10.9 dst 10.10.10.10
*Apr 18 18:19:52.107: FIBipv4-packet-proc: packet routing succeeded
*Apr 18 18:19:52.107: IP: s=10.10.10.9 (local), d=10.10.10.10 (FastEthernet0/1), len 40, sending
*Apr 18 18:19:52.111:     TCP src=20596, dst=49, seq=1187787266, ack=3815757363, win=4100 ACK
080014D0:                   45000028 678C0000          E..(g...
080014E0: FF062C1D 0A0A0A09 0A0A0A0A 50740031  ..,.........Pt.1
080014F0: 46CC3202 E36FD633 50101004 F4920000  FL2.coV3P...t...
08001500:
*Apr 18 18:19:52.127: IP: s=10.10.10.9 (local), d=10.10.10.10 (FastEthernet0/1), len 40, sending full packet
*Apr 18 18:19:52.131:     TCP src=20596, dst=49, seq=1187787266, ack=3815757363, win=4100 ACK
080014C0:                       0200 4C4F4F50            ..LOOP
080014D0: CA000CB8 00060800 45000028 678C0000  J..8....E..(g...
080014E0: FF062C1D 0A0A0A09 0A0A0A0A 50740031  ..,.........Pt.1
080014F0: 46CC3202 E36FD633 50101004 F4920000  FL2.coV3P...t...
08001500:

First we save it in a ascii/text file (i.e. "test.dump") and we give it as input to the "ciscodump2text" program.

tassos$ ciscodump2text test.dump > test.text

The created "test.text" file contains the following :

# Packet 1
00000000 45 00 00 50 67 8B 00 00 FF 06 2B F6 0A 0A 0A 09 #
00000010 0A 0A 0A 0A 50 74 00 31 46 CC 31 DA E3 6F D6 17 #
00000020 50 10 10 20 9F 96 00 00 C0 01 01 00 99 64 8E 6A #
00000030 00 00 00 1C B8 14 5E C8 A8 B3 C2 B9 3E C1 2A 1F #
00000040 AA 40 DE 66 D7 42 9C 89 0B F9 11 F3 C7 24 9F 5F #
# Packet 2
00000000 02 00 4C 4F 4F 50 CA 00 0C B8 00 06 08 00 45 00 #
00000010 00 50 67 8B 00 00 FF 06 2B F6 0A 0A 0A 09 0A 0A #
00000020 0A 0A 50 74 00 31 46 CC 31 DA E3 6F D6 17 50 10 #
00000030 10 20 9F 96 00 00 C0 01 01 00 99 64 8E 6A 00 00 #
00000040 00 1C B8 14 5E C8 A8 B3 C2 B9 3E C1 2A 1F AA 40 #
00000050 DE 66 D7 42 9C 89 0B F9 11 F3 C7 24 9F 5F #
# Packet 3
00000000 45 00 00 28 67 8C 00 00 FF 06 2C 1D 0A 0A 0A 09 #
00000010 0A 0A 0A 0A 50 74 00 31 46 CC 32 02 E3 6F D6 33 #
00000020 50 10 10 04 F4 92 00 00 #
# Packet 4
00000000 02 00 4C 4F 4F 50 CA 00 0C B8 00 06 08 00 45 00 #
00000010 00 28 67 8C 00 00 FF 06 2C 1D 0A 0A 0A 09 0A 0A #
00000020 0A 0A 50 74 00 31 46 CC 32 02 E3 6F D6 33 50 10 #
00000030 10 04 F4 92 00 00 #

Then, we convert this new text file into a pcap file by using the "text2pcap" program, which is included with Wireshark.

tassos$ text2pcap.exe" -d test.text test.pcap
Input from: test.text
Output to: test.pcap
Start new packet
Start new packet
Wrote packet of 80 bytes at 0
Start new packet
Wrote packet of 94 bytes at 80
Start new packet
Wrote packet of 40 bytes at 174
Wrote packet of 54 bytes at 214

-------------------------
Read 4 potential packets, wrote 4 packets

The resulting pcap file "test.pcap" can be opened for further processing with Wireshark.

That way you can very easily create pcap files of almost everything happening on your router.

Notes : The "dump" option is supported since 12.0 IOS. Latest IOS includes EPC, which makes the whole capture & convert-to-pcap process much easier.

PS : I'm not a very good perl programmer (although i have written a lot of custom perl scripts for my job), so someone playing with perl for years will probably produce a more compact "perlish" code. I just tried to interpret my logic into perl code.