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 that its programming dictates. Packet sniffers merely watch...
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 immediate benefits. Unfortunately a problem also appeared...
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 and discuss how to connect to the other routers and switches...
Cisco CCNP / BSCI: Using The OSPF Command "Area Range"
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, but knowing where and when to summarize routes. It will not surprise any CCNA or CCNP certification candidate that OSPF gives us the most options for route summarization, and therefore more details to know!
OSPF offers us two options for route summarization configurations. In a previous tutorial, we looked at the "summary-address" command, and today we'll look at the proper use of the "area range" command.
The "area range" command should be used on an Area Border Router (ABR) to summarize routes being advertised from one OSPF area to another. In this tutorial, R1 is acting as an ABR, with interfaces in
both Area 0 and Area 1. Four loopbacks have been placed into R1's Area 1.
R1(config)#router ospf 1
R1(config-router)#network 126.96.36.199 0.255.255.255 a 1
R1(config-router)#network 188.8.131.52 0.255.255.255 a 1
R1(config-router)#network 184.108.40.206 0.255.255.255 a 1
R1(config-router)#network 220.127.116.11 0.255.255.255 a 1
The routing table of an OSPF neighbor, R2, shows all four routes.
R2#show ip route ospf
18.104.22.168/32 is subnetted, 1 subnets
O IA 22.214.171.124 [110/65] via 126.96.36.199, 00:18:52, Serial0
188.8.131.52/32 is subnetted, 1 subnets
O IA 184.108.40.206 [110/65] via 220.127.116.11, 00:18:42, Serial0
18.104.22.168/32 is subnetted, 1 subnets
O IA 22.214.171.124 [110/65] via 126.96.36.199, 00:18:32, Serial0
188.8.131.52/32 is subnetted, 1 subnets
O IA 184.108.40.206 [110/65] via 220.127.116.11, 00:18:32, Serial0
To keep the routing tables of downstream routers smaller but still have the desired IP connectivity, we can use the area range command on R1 to summarize these four routes. The key to keep in mind with the area range command is that the area number given in the command is the area containing the destinations, NOT the area that will receive the summary route.
R1(config)#router ospf 1
R1(config-router)#area 1 range 18.104.22.168 252.0.0.0
R2 now shows a single summary route that can be used to reach all four remote networks.
R2#show ip route ospf
O IA 22.214.171.124/6 [110/65] via 126.96.36.199, 00:00:21, Serial0
Interestingly enough, there's now an additional route in R1's routing table.
R1#show ip route ospf
O 188.8.131.52/6 is a summary, 00:07:53, Null0
When you configure summary routes in OSPF, a route to null0 will be installed into the OSPF routing table of the router performing the summarization. This helps to prevent routing loops. Any packets destined for the routes that have been summarized will have a longer match in the routing table, and packets that do not match one of the summarized routes but do match the summary route will be dropped.
About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (www.thebryantadvantage.com), 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!