Recent Articles

Tips For Terminal Servers
Here's a list of tips to help ensure your Terminal Servers are functioning as efficiently as possible. These are rules I always abide by. Have a look, they may help you too... 1.) Sort your profiles out. Profiles are the biggest cause of slow logons and many other issues in Terminal...

Cisco CCNP / BSCI: Using The OSPF Command...
Your BSCI and CCNP exam success depends on knowing the details, and one such detail is knowing the proper way to summarize routes in OSPF. Route summarization is not just a test of your binary conversion abilities...

OSPF Route Redistribution Review
OSPF route redistribution is an important topic on the BSCI exam, and its a topic full of details and defaults that you need to know for the exam room and the job. To help you pass the BSCI exam, heres a quick review of some of the OSPF route redistribution basics.

Changing Root Bridge Election Results
Your BCMSN and CCNP studies will include mastering the details of Spanning Tree Protocol (STP). While you learned some of these details in your CCNA studies, quite a bit of it may be new to you. Before going on to the intermediate and advanced STP features, lets...

The Evil Packet Sniffer
A "Packet Sniffer" is a utility that sniffs without modifying the network's packets in any way. By comparison, a firewall sees all of a computer's packet traffic as well, but it has the ability to block and drop any packets...

Losing Data Over VPN
Sometimes change is good, sometimes it's bad, and sometimes it's a mixed bag. Such was the case recently when a customer switched a remote office from a 56K line to using a Kerio VPN over Internet connections. The 56K line was slow and expensive, so the switch had...

ColdFusion And Server Monitoring
Unlocking the CF Server Black Box. How to answer questions about your server. How is it doing? What templates/queries are slow? New tool: CF Server Monitor. Monitors requests via all paths (template, CFC, web service, gateway, Flash Remoting) Has minimal...

ISIS Router Types
To pass the BSCI exam and earn your CCNP, youŽve got to know ISIS inside and out. There are many similarities between ISIS and OSPF, but one major difference is that ISIS has three different types of routers - Level 1 (L1), Level 2 (L2), and L1/L2. L1 routers are...

Configuring An Access Server
As your CCNA / CCNP home lab expands, an access server such as the Cisco 2509 or 2511 is one of the best investments you can make. In this article, weŽll look at the basic configuration for an access server...


Master Route Redistribution

By Chris Bryant

To be successful on the BSCI exam and in earning your CCNP, you've got to master route redistribution.

This isn't as easy as it sounds, because configuring route redistribution is only half the battle. Whether it's on an exam or in a real-world production network, you've got to identify possible points of trouble before you configure route redistribution - and you need to be able to control redistribution as well. You may have an OSPF domain with 100 routes, but only need to redistribute 10 of them into a neighboring RIPv2 domain. You've got to know how to do that, and one method is to use a distribute-list.

A distribute-list is an access-list that is used to determine what routes can and cannot be redistributed. Distribute-lists let you specify what routes will be filtered from the process. You can use standard or extended ACLs, and you can filter routes that are coming into a routing process or being injected into another process.

In the following example, R1 is redistributing RIP routes into OSPF, but only wants to advertise network /24 to other OSPF routers. An ACL will be written to match that particular network, and then the distribute-list will be written under the routing process. I'm going to show you the IOS Help output for the distribute-list command, and please note that routing updates can be controlled at the interface level or protocol level.

R1(config)#access-list 24 permit

R1(config)#router ospf 1

R1(config-router)#redistribute rip subnets

R1(config-router)#distribute-list 24 ?

in Filter incoming routing updates

out Filter outgoing routing updates

R1(config-router)#distribute-list 11 out ?

Async Async interface

BRI ISDN Basic Rate Interface

BVI Bridge-Group Virtual Interface

CTunnel CTunnel interface

Dialer Dialer interface

Low Rate eCommerce & Retail Plans

Ethernet IEEE 802.3

Lex Lex interface

Loopback Loopback interface

Multilink Multilink-group interface

Null Null interface

Serial Serial

Tunnel Tunnel interface

Vif PGM Multicast Host interface

Virtual-Template Virtual Template interface

Virtual-TokenRing Virtual TokenRing

bgp Border Gateway Protocol (BGP)

connected Connected

egp Exterior Gateway Protocol (EGP)

eigrp Enhanced Interior Gateway Routing Protocol (EIGRP)

igrp Interior Gateway Routing Protocol (IGRP)

ospf Open Shortest Path First (OSPF)

rip Routing Information Protocol (RIP)

static Static routes

R1(config-router)#distribute-list 11 out rip

Using distribute-lists does guard against routing loops, but they have other purposes. You may have a network segment that should be kept secret from the rest of your company; a distribute-list can filter that segment's network number from the redistribution process. In this way, distribute-lists serve as a basic form of network security. (Very basic. I wouldn't sell that firewall on ebay if I were you.)

Keeping such networks out of routing updates and routing tables throughout the network has the side effect of reducing routing update overhead as well.

About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (, home of FREE CCNA and CCNP tutorials and daily exam questions, as well as The Ultimate CCNA and CCNP Study Packages.

For a FREE copy of his latest e-books, "How To Pass The CCNA" or "How To Pass The CCNP", and for free daily exam question, visit the website and download your copies!

About NetworkNewz
NetworkNewz editors, writers and contributors focus on both the big picture and the details of networking. At NetworkNewz our goal is to deliver to you The Key To Network Management.

NetworkNewz is brought to you by:

-- NetworkNewzis an iEntry, Inc. publication --
iEntry, Inc. 2549 Richmond Rd. Lexington KY, 40509
2007 iEntry, Inc.  All Rights Reserved  Privacy Policy  Legal

archives | advertising info | news headlines | newsletters | comments/feedback | submit article

The Keys To Network Management Ask Questions in the Networking Forum NetworkNewz News Archives About Us Feedback NetworkNewz Home Page About Article Archive News Downloads WebProWorld Forums Jayde iEntry Advertise Contact