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Friday, May 12, 2017

Digital Disruption in Service Providers

Every industry can be digitally disrupted - even those that claim to provide the very digital transformation enterprises so desperately seek.

The true benefit of software-defined networking is not separation of control plane and data plane - that doesn't work at scale. It's not easier centralized control and the end of command line with more fancy acronyms like YANG, XML-RPC and REST APIs. The "revolutionary" idea is the separation of the network layer into physical connectivity and logical connectivity. I quote "revolutionary" as tongue-in-cheek - the OSI model always had a separate physical layer and network layer, but in the long move from circuits to fully-managed, bundled MPLS, we seem to have forgotten that.

Wednesday, May 10, 2017


A seemingly normal DNS packet:

ETH: dst:98:76:54:32:10:ab  src:ab:cd:ef:12:34:56  type:0x0800
IPv4: version:4  hlen:5  tos:0x00  length:190  id:44821
IPv4: flags:0x00  offset:0  ttl:128  protocol:0x11  checksum:0xb060
IPv4: src:  dst:
UDP: src:53  dst:13245  length:170  checksum:0x8756
DNS: id:21817  qr:1  opcode:0  flags:0x18  rcode:0
DNS: qdCount:1  anCount:4
DNS: nsCount:0  arCount:0
DNS::Question: name:www.www.com
DNS::Question: type:1  class:1
DNS::RR: name:www.www.com
DNS::RR: type:5  class:1  ttl:64  rdlength:16
DNS::RR::CNAME: cname:www.Johnny.com
DNS::RR: name:www.www.com
DNS::RR: type:5  class:1  ttl:64  rdlength:17
DNS::RR::CNAME: cname:www.Fingers.com
DNS::RR: name:www.www.com
DNS::RR: type:1  class:1  ttl:64  rdlength:4
DNS::RR::A: address:
DNS::RR: name:www.www.com
DNS::RR: type:1  class:1  ttl:64  rdlength:4
DNS::RR::A: address:

But upon some decoding ...

Thursday, May 04, 2017

Net::SSH2 Upgrade Access to Cisco

I upgraded my Strawberry Perl to 5.24 and my GNS3 test lab for SSH access via CRAPPS suddenly didn't work.

Knowing the Perl version changed, I checked and the Net::SSH2 version changed (0.58 to 0.63). Troubleshooting was pretty easy - just a quick Perl script to open a connection and die on failure with error:

use strict;
use warnings;
use Net::SSH2;

my $ssh2 = Net::SSH2->new();
$ssh2->connect('') or $ssh2->die_with_error;
print "Success\n";

The error was: Unable to exchange encryption keys (-8 LIBSSH2_ERROR_KEY_EXCHANGE_FAILURE). OK, so I said troubleshooting was easy ... the solution ... maybe not so much?


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