INTERPRETING CONFIGURATION REGISTERS ON CISCO ROUTERS

The Purpose of the Configuration Register

The configuration register can be used to change router behavior such as how the router boots whether you would like it to boot into rommon mode for recovery purpose such as copying an IOS into the router via xmodem protocol, ignore the configuration or disable boot messages and change the console speed settings.

The configuration register can be verified through the "show version" command:

Router#show version
Cisco Internetwork Operating System Software
IOS (tm) 2500 Software (C2500-JS-L), Version 12.1(5), RELEASE

SOFTWARE (fc1)
Copyright (c) 1986-2000 by cisco Systems, Inc.
Compiled Wed 25-Oct-00 05:18 by cmong
Image text-base: 0x03071DB0, data-base: 0x00001000
ROM: System Bootstrap, Version 5.2(8a), RELEASE SOFTWARE
BOOTFLASH: 3000 Bootstrap Software (IGS-RXBOOT), Version 10.2(8a),

RELEASE SOFTWARE (fc1)
Router uptime is 7 minutes
System returned to ROM by reload
System image file is "flash:c2500-js-l_121-5.bin"
cisco 2500 (68030) processor (revision D) with 16384K/2048K bytes of memory.
Processor board ID 03867477, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
SuperLAT software (copyright 1990 by Meridian Technology Corp).
TN3270 Emulation software.
1 Token Ring/IEEE 802.5 interface(s)
2 Serial network interface(s)
32K bytes of non-volatile configuration memory.
16384K bytes of processor board System flash (Read ONLY)
Configuration register is 0x2102

CNAME

CNAME is short for canonical name which is a type of resource record (resource records include A record, MX, DNAME, AAAA for IPv6 etc.) found in a DNS database. A CNAME specifies that the domain name is an alias of another canonical domain name and is used to point to an already existing A record. A few of CNAME uses is too mask a domain, , point to another subdomain, point several services such as ftp and www to a single IP address, point to an outside domain or service.

The uses of CNAME are summarized below:

1. CNAME is used to point or alias to another domain. Here is an example:

[root@dns1 forward]# more example.com.db
;
$TTL 43200
@ IN SOA dns1.example.com.ph. postmaster.example.com.ph. (
2010021002 ; Serial
1800 ; Refresh - 30 minutes
300 ; Retry - 5 minutes
604800 ; Expire - 1 week
2880 ) ; Minimum - 8 hours

IN NS dns1.example.com.ph.
IN NS dns2.example.com.ph.
only IN A 10.1.1.1
carlo IN CNAME only

The above example is a real file zone taken from a unix base DNS server obviously masked for confidentiality. In this example, the subdomain is carlo.example.com which is pointed to another domain which is only.example.com which already has an existing A record.

Another example below:

HOW TO READ TRACEROUTE AND TROUBLESHOOT USING TRACEROUTE

Traceroute is a diagnostic utility present and can be run in all systems like windows, Unix and operating systems in switches, routers etc. Unlike ping which only tests the connectivity between endpoints and doesn't have an output of letting you know where the problem is once you received a destination unreachable message, traceroute provides a detailed output of the path it traverses. The output contains the public IP addresses the packet arrives in and the providers connection to upstream providers.

Traceroute is a very helpful tool in troubleshooting internet connection. Most administrators use this utility to check their internet connection to their ISP in case they are experiencing slow or intermittent internet connection. Traceroute provides a detailed output if the traceroute is complete and has reached its destination (example, www.google.com or a address of a remote server) , latency measurement, number of hops it takes before reaching the destination. Basically traceroute diagnose the health of your internet connection if it is still efficient. Usually traceroute is up to 30 hops maximum and at some point, traceroutes at the end may end up in destination unreacheable message before it reaches the destination because the network where the destination IP address has already been firewalled. But this is just ok as long as the trace is complete and has traversed the provider and you can connect to the destination.

Trace route determines if the latency is within the customer's LAN, the providers network or to their upstream ISP's. Traceroute also becomes the basis for ISP engineers if they need to reroute the destination to a different upstream if latency has been identified to be too high. They usually check for number of hops cause less number of hops means less travel and less latency means faster connection.

Below are a sample traceoute and how to read and troubleshoot them.

CHANGES IN CCNP EXAM

Over the past years, I have seen CISCO certifications evolved into more focused levels as well as the most coveted certification in the IT industry. Back then when I was still in college, CCNA exams were confined to the privileged ones because of its cost. Until it became affordable that it became a commodity in the IT industry. At that point, CCNA exams branched out into different specializations including CCNA security, CCNA voice and CCNA wireless which also paved the way for specialized CCNP and CCIE certifications. Apart from that, individual modules in each certification changes through the course of time. That includes the latest changes in CCNP exam.

The changes in the CCNP exams are reflected below:

CISCO PASSWORD RECOVERY FOR FIXED CATALYST SWITCHES

Fixed catalyst switches includes layer 2 switches 2900XL/3500XL, 2940, 2950/2955, 2960 and 2970 series as well as layer 3 switches 3550, 3560, and 3750 switches. Layer 2 switches means they are not capable of layer 3 functionality such as routing and mainly used for switching functionality. Fixed switches mean that the devices are not modular unlike the big boxes which has different kinds of modules you can insert into.

Procedure for password recovery