Popular DOC-CD

Where the $%#@ is it? Some Popular DOC-CD Locations

By Anthony Sequeira, #15626

Hello faithful blog readers. We all know there are some real treasures in the DOC-CD that can assist dramatically in the lab exam. Here are some of our reader’s favorites. Thanks to my friend Ruhann over in South Africa for the post idea!

All navigation begins from http://www.cisco.com/web/psa/products/tsd_products_support_configure.html

I. Bridging and Switching

II. IP IGP Routing

III. BGP

a. Best Path Selection

Cisco IOS Software - 12.2 S Family - 12.2 SB - C.G. - Cisco IOS IP Configuration Guide, Release 12.2 - Part 2: IP Routing Protocols - Configuring BGP - How BGP Selects Paths

b. Regular Expressions

Cisco IOS Software - 12.4 Family - 12.4 Mainline - C.G. - Cisco IOS Terminal Services Configuration Guide, Release 12.4 - Appendixes - Regular Expressions

IV. IP and IOS Features

a. NTP

Cisco IOS Software - 12.4 Family - 12.4 Mainline - C.G. - Cisco IOS Network Management Configuration Guide, Release 12.4 - Performing Basic System Management - Setting Time and Calendar Services

V. IP Multicast

VI. QoS

a. RTP Port Range

Cisco IOS Software - 12.4 Family - 12.4 Mainline - Reference Guides - Command References - Cisco IOS Quality of Service Solutions Command Reference - frame-relay ip rtp priority

VII. Security

a. ACL Favorites

Security - Firewall Appliances - Cisco ASA 5500 Series Adaptive Security Appliances - C.G. - Cisco Security Appliance Command Line Configuration Guide, Version 8.0 - Reference - Addresses, Protocols, and Ports

b. Regular Expression

Cisco IOS Software - 12.4 Family - 12.4 Mainline - C.G. - Cisco IOS Configuration Fundamentals Configuration Guide - Part 1: Using the Cisco IOS Command-Line Interface - Understanding Regular Expressions

**Common ports : http://packetlife.net/cheatsheets/#reference

Debug output collection

Useful command for logging on console from IE.

When you work with a remote rack by using an access-server (e.g. 25xx) with the async lines connected to the console ports of the pod’s routers, you effectively have only one terminal window opened. Using ctrl-Shift-6-x you can quickly switch between terminal lines; however, if you need to monitor “debug” command output on one terminal line, while performing some activity on the other you may face some difficulties.

For example, when you enable debug crypto isakmp on one router, and then switch to the other router, to generate packets with ping command, you may lose some of the debugging output, while switching back to the original router. Two obvious ways to resolve this issue exist: first one - open multiple terminal windows; next one - use logging buffered command to collect the debug logs into logging buffer. The third, not so well-known way to cope with the issue, is to use service telnet-zeroidle command on the access server.

What this command does, is announces TCP receive window with the value of zero for “idle” (currently non-active) connections. How does this work? When a TCP “server” is told that the other side’s TCP receive window is zero, the server starts buffering data to be send, until the other side “un-shrinks” the window again. Now, since all sessions from an access-server are effectively reverse-telnet connections to the access-server itself, by advertising TCP window value of zero, we make access-server buffer router’s console output (e.g. from debug commands), until the respective session becomes active again. In effect, with service telnet-zeroidle enabled, you may start, say, debug crypto isakmp on one router, switch to other, type ping x.x.x.x, then get back to the original router just to grab all the debug output at once - without any loss! Just make sure, your large debugging output runs fit into TCP xmit buffer, and don’t be scared by flood of output when you get back to an idle connection!