Blog Posts in 2007

December 2007

New look (25 Dec 2007)
Display open TCP and UDP ports (20 Dec 2007)
What is a BGP RIB failure (19 Dec 2007)
EEM CLI patterns are not context sensitive (17 Dec 2007)
Making the case for Layer 2 and Layer 3 VPNs (14 Dec 2007)
MPLS Traffic Engineering without a Link State routing protocol (11 Dec 2007)
Mandatory EEM CLI commands (10 Dec 2007)
BGP fast session deactivation also speeds up session establishment (06 Dec 2007)
Execute CLI commands with prompts in EEM (04 Dec 2007)
BGP without MPLS? (03 Dec 2007)

November 2007

BGP Fast Session Deactivation (29 Nov 2007)
Configure DNS Servers Through IPCP (28 Nov 2007)
Enhanced show interfaces command (27 Nov 2007)
Can I combine EEM applets with Tcl shell? (26 Nov 2007)
Kron: poor-man's cron (22 Nov 2007)
Install default route with PPP (21 Nov 2007)
Enable password or enable secret? (20 Nov 2007)
Emulate dialup links with serial lines (19 Nov 2007)
IPv6 Deployment: Time for Action? (16 Nov 2007)
Use BGP Default Route to Replace Static Routing (15 Nov 2007)
Type 7 decryption in Cisco IOS (14 Nov 2007)
Show active IOS processes (13 Nov 2007)
Persistent EEM variables (12 Nov 2007)
Ones Are Slower than Zeroes (11 Nov 2007)
Impact of Netflow accounting (10 Nov 2007)
Routing table profiling (08 Nov 2007)
Catch Skype with Flexible Packet Matching (08 Nov 2007)
Back to the roots: it all started with SDLC (06 Nov 2007)
React to excessive jitter with EEM (05 Nov 2007)
For the oldtimers: swamped with zeroes (03 Nov 2007)
MPLS Traffic Engineering myths (02 Nov 2007)
Download router configurations via TFTP (01 Nov 2007)

October 2007

Remove the configuration prompt (31 Oct 2007)
More Details on OSPF Route Filters (30 Oct 2007)
Send an e-mail when an interface goes down (29 Oct 2007)
Debugging cached CEF adjacencies (25 Oct 2007)
OSPF Neighbors Stuck in EXSTART (24 Oct 2007)
GRE tunnel keepalives (23 Oct 2007)
Tabular display of interface MTUs (22 Oct 2007)
The tale of the three MTUs (17 Oct 2007)
SNMP with Tcl (15 Oct 2007)
War story: almost zero is not good enough (14 Oct 2007)
Turn your flash card into an ATA drive (11 Oct 2007)
mturoute: trace mode output (10 Oct 2007)
Display IP packet filters attached to router's interfaces (08 Oct 2007)
IOS 12.4T features summarized on one page (07 Oct 2007)
mturoute: ping-mode output (06 Oct 2007)
Show IP access lists attached to an interface (04 Oct 2007)
Log the NTP events (03 Oct 2007)
OSPF Router-Id Does Not Change When the Interface IP Address Changes (02 Oct 2007)

September 2007

Update: mturoute (30 Sep 2007)
mturoute: A utility that measures hop-by-hop path MTU (29 Sep 2007)
Stop Inter-VRF static route leaking (27 Sep 2007)
Router as a TFTP server (26 Sep 2007)
Material worth reading (25 Sep 2007)
EEM syslog messages look like debugging messages (24 Sep 2007)
Five routers on your laptop (22 Sep 2007)
Frame Relay congestion management (20 Sep 2007)
Assigning Server IP addresses with DHCP (19 Sep 2007)
CEF accounting (18 Sep 2007)
Increased Number of OSPF processes in MPLS VPN Environments (13 Sep 2007)
Logging to flash disk (11 Sep 2007)
DNS resolver package for IOS Tcl (10 Sep 2007)
Static routing with Catalyst 3750: and the winner is … (08 Sep 2007)
Workaround: track the actual IP routing status of an interface (06 Sep 2007)
Get Creative: Static Routing with Catalyst 3750 (05 Sep 2007)
Persistent DHCP bindings stored in NVRAM (04 Sep 2007)
Using Tcl packages on Cisco IOS (03 Sep 2007)
Don't miss the obvious (02 Sep 2007)

August 2007

DHCP conflict logging: the true story (30 Aug 2007)
Track interface IP routing detects incorrect interface state (29 Aug 2007)
MPLS LDP Autoconfiguration (28 Aug 2007)
Insert Responses to Command Prompts in Tclsh (27 Aug 2007)
Skip the “show ip route” legend (25 Aug 2007)
Install a Static Route When an IP Address Is NOT Reachable (23 Aug 2007)
Warm reload does not change the config register (22 Aug 2007)
DHCP-based static routes (21 Aug 2007)
Reload a Router from Tcl Script (20 Aug 2007)
Import DHCP options from an upstream DHCP server (16 Aug 2007)
OSPF Graceful Shutdown (14 Aug 2007)
Default DHCP client-id (09 Aug 2007)
Example: Tcl script with command-line parameters (08 Aug 2007)
Re-enable debugging without EEM (07 Aug 2007)
Sample configuration: periodic upload of router configuration (02 Aug 2007)
Conditional OSPF Default Route: Tested Configuration (01 Aug 2007)

July 2007

Update: The “show ip interface” command I've always wanted to have (30 Jul 2007)
Changing the Format of IP Routes (26 Jul 2007)
Update: Preparing for the MPLS CCIP exam (25 Jul 2007)
Inspection of router-generated traffic does not recognize DHCP client traffic (24 Jul 2007)
DHCP and BOOTP coexistence (19 Jul 2007)
Totally Stealthy Router (17 Jul 2007)
Be Smart When Using the OSPF Network Statement (12 Jul 2007)
Update: Inspect router-generated traffic (10 Jul 2007)
Redundant DHCP server (05 Jul 2007)
Network Statements Are No Longer Needed in OSPF Configuration (03 Jul 2007)

June 2007

Using MPLS VPN Books to Study for the CCIP Exam (29 Jun 2007)
OSPF Default Route: Design Scenarios (28 Jun 2007)
Inserting Default Route Into OSPF (27 Jun 2007)
Display per-process memory usage (26 Jun 2007)
The “show ip interface” command I've always wanted to have (25 Jun 2007)
MPLS Ping and Traceroute (21 Jun 2007)
Closed versus Filtered ports (20 Jun 2007)
ARP timeout resolution is implemented in minutes (19 Jun 2007)
Port number not shown in access-list log output (14 Jun 2007)
ARP entries are periodically refreshed if you use CEF switching (13 Jun 2007)
Router Responses to Port Scans (12 Jun 2007)
Re-enable debugging on router reload (11 Jun 2007)
Default interface configuration command (07 Jun 2007)
Inspect router-generated traffic (06 Jun 2007)
DHCP Response Sets the Default Route (05 Jun 2007)
Fix the IOS quiet mode for the IOS HTTP(S) server (04 Jun 2007)

May 2007

Catching all syslog messages (31 May 2007)
The DNS configuration "challenges" (30 May 2007)
Warm upgrade (29 May 2007)
Reload EEM Tcl policy with help of Tcl shell (28 May 2007)
Unbundle DNS settings from DHCP client (24 May 2007)
Change the Telnet font color from a Cisco router (23 May 2007)
DNS resolver in Cisco IOS is auto-configured with parameters from a DHCP reply (22 May 2007)
Periodic execution of IOS show commands (21 May 2007)
Protecting the primary DNS server on your router (19 May 2007)
Unicode IPS vulnerability: more details (16 May 2007)
DNS views are broken in release 12.4(11)T (15 May 2007)
Command Authorization Fails with EEM applet or Tcl policy (14 May 2007)
Background Continuous Ping from a Router (10 May 2007)
What is a cached CEF adjacency? (09 May 2007)
The self zone in zone-based firewall configuration (08 May 2007)
Use Tcl script to change the interface status (07 May 2007)
IOS Tclsh resources (06 May 2007)

April 2007

When is the default-gateway used? (26 Apr 2007)
Sinkholes and blackholes (25 Apr 2007)
Save IOS printouts in a file (25 Apr 2007)
Summarize IOS printouts (example: Frame Relay DLCIs) (24 Apr 2007)
Fix router configuration after a reload (23 Apr 2007)
Change the username/password prompt with AAA (19 Apr 2007)
Changes in EIGRP Summary Address Are no Longer Disruptive (18 Apr 2007)
Continuous ping from a router (17 Apr 2007)
Execute multiple commands at once (16 Apr 2007)
Display top CPU processes on the router (12 Apr 2007)
Warm reload (11 Apr 2007)
Why is the first ping lost? (10 Apr 2007)
Tclsh Command Line Parameters (09 Apr 2007)
Reload a Router When Ping Fails (05 Apr 2007)
Authenticating HTTP requests with AAA (04 Apr 2007)
Executing IOS Commands from Tcl Shell (02 Apr 2007)

March 2007

EIGRP Load Balancing Based on Interface Load (31 Mar 2007)
More command works as hex dump if needed (29 Mar 2007)
Execute show commands while configuring a router (28 Mar 2007)
One-time passwords on Cisco routers (27 Mar 2007)
Where does the Tcl output go? (26 Mar 2007)
Configure local authentication with AAA (22 Mar 2007)
Local usernames with no password (21 Mar 2007)
One-line extended ping (20 Mar 2007)
Running Tcl Procedures from Cisco IOS CLI (19 Mar 2007)
MPLS VPN half-duplex VRF works only on virtual template interface (16 Mar 2007)
Executing a command upon user login (15 Mar 2007)
Display Configuration of a Single Interface (14 Mar 2007)
EIGRP Goodbye Message (12 Mar 2007)
Can you disable the reload command? (11 Mar 2007)
Enhanced password security for local usernames (09 Mar 2007)
Stop extended ping or traceroute command (08 Mar 2007)
Save the approximated date-and-time in NVRAM (07 Mar 2007)
Where did the CBAC go? (06 Mar 2007)
Reload EEM Tcl policy with an EEM applet (02 Mar 2007)

February 2007

The versatile more command (28 Feb 2007)
Filter sections of your running configuration (27 Feb 2007)
Store your EEM Tcl policies in NVRAM (24 Feb 2007)
Simulate interface counters with QoS policy-map (23 Feb 2007)
Minimum SDM configuration (22 Feb 2007)
Not All Static Routes Were Created Equal (20 Feb 2007)
Reliable static routing (16 Feb 2007)
Embedded Event Manager scripting center (15 Feb 2007)
Frame Relay local switching (13 Feb 2007)
Unequal load split with static routes (12 Feb 2007)
Log IP SLA failures (10 Feb 2007)
Reporting a state of an IP route (09 Feb 2007)
Unequal Cost Load-Sharing with MPLS TE (08 Feb 2007)
Weird VTY numbers in IOS release 12.4T (07 Feb 2007)
What is the sl_def_acl access list (06 Feb 2007)
Default Action in Firewall Policy Maps (05 Feb 2007)
Use access-lists to filter IP packets with IP options (04 Feb 2007)
Don't use copy commands in EEM applets (01 Feb 2007)

January 2007

Cisco IOS web server with no enable password (31 Jan 2007)
Default username on Cisco routers (29 Jan 2007)
Firewalls kill TCP performance when faced with out-of-order packets (26 Jan 2007)
VTY access-class accepts extended and named access lists (25 Jan 2007)
Disable the "more" prompt (23 Jan 2007)
Cisco IOS Login Enhancements (22 Jan 2007)
CEF punted packets (19 Jan 2007)
CEF punt adjancency (19 Jan 2007)
Reload the router from an interim privilege level (17 Jan 2007)
Count the logging messages (16 Jan 2007)
Per-Port CEF Load Balancing (14 Jan 2007)
Improve the convergence of static routes (10 Jan 2007)
Enhanced OSPF Adjacency Logging (09 Jan 2007)
How do I stop all logging done by the router (09 Jan 2007)
Disable console logging (07 Jan 2007)
"You've asked for it" series (07 Jan 2007)
Remove timestamps from syslog messages (03 Jan 2007)