Add Remote Backup Services to your existing business, or start a profitable Internet-based online backup service for a high profit recurring revenue stream.
Click here for more info.

Recent Articles

Dynamic Trunking Protocol (DTP)
When you´re studying to pass the BCMSN exam on the way to earning your CCNP certification, you´re going to add to your CCNA knowledgebase every step of the way.

Static VLANs
BCMSN exam success and earning your CCNP certification requires you to add to your knowledge of VLAN configuration.

Keep in touch (tcp keepalives etc.)
You can't please everyone, so you got to please yourself...I don't imagine Ricky Nelson was thinking about tcp timeouts and keepalives in the 70's...

Senator Proposes Net Neutrality Bill
Ron Wyden (D-Or) has introduced legislation to prevent telecoms and cable companies from developing a two-tiered network where fees would be charged to content providers to prioritize their Internet traffic...

Open Source Vyatta Takes On Hardware

After years of open source projects like Linux and MySQL taking share from proprietary software companies, hardware makers like Cisco and Juniper get to experience the heart-stopping terror of open source hardware hitting the market...

Secure Routers Go Through Ceiling In 2005
A new study from Infonetics Research reported big numbers for secure routers in 2005...

Net Neutrality Divides On Party Lines
The potential to future innovators to build on the success of the Internet may well hinge on network neutrality, but the two major political parties in Congress see the issue differently. In a nutshell, or at least in a story appearing on ZDNet, Democrats noted in the article side with the...

What is Microsoft Terminal Server?

Microsoft Terminal Server is a component of the Windows operating system that allows users to remotely access servers and applications over the internet or a local area network...

Juniper Battles "Defamers And Libelers"
Comments made by as many as ten people using the message boards at the Light Reading website have the networking company ticked off and filing suit against "defamers and libelers."

Using The BGP Command “Update-Source”
When you start preparing for your CCNP exam, particularly the BSCI exam, you´re introduced to Border Gateway Protocol (BGP) configurations.

Cisco CCNA / CCNP Home Lab Setup: How To Configure Reverse Telnet
Occasionally, during your CCNA and CCNP studies, you´ll run into a term that just doesn´t quite make sense to you.

Passing The CCNA and CCNP: Three Myths About Cisco Exams
One of the drawbacks to the Internet is that it allows myths and "friend of a friend" stories to spread quickly, and usually the story becomes more exaggerated as it's passed along.

Router on a Stick
For CCNA and CCNP candidates, it's hard not to laugh the first time you hear the phrase "router on a stick".


BGP Adjacency States

By Chris Bryant

To pass the BSCI exam, earn your CCNP certification, and become an outstanding networker, you´ve got to master the many details of BGP - and trust me, there are a lot of details to master!

Before you get into the more advanced features of BGP, you should have the fundamentals down cold, and one of those fundamentals is knowing the BGP adjacency states. This will allow you to successfully analyze and troubleshoot BGP peer relationships.

In the following example, a BGP peering is being created between R1 and R3.

R1(config-router)#neighbor remote-as 200

BGP speakers do not have to be in the same AS to become peers. To verify that the remote BGP speaker has become a peer, run show ip bgp neighbor.

R1#show ip bgp neighbor

BGP neighbor is, remote AS 200, external link

BGP version 4, remote router ID

BGP state = Active

Last read 00:01:39, hold time is 180, keepalive interval is 60 seconds

Received 0 messages, 0 notifications, 0 in queue

Sent 0 messages, 0 notifications, 0 in queue

Route refresh request: received 0, sent 0

Default minimum time between advertisement runs is 30 seconds

The output here can be a little misleading the first time you read it. The first highlighted line shows is a BGP neighbor, is located in AS 200, and is an external link, indicating that the neighbor is in another AS entirely. The second highlighted line shows the BGP state as Active. This sounds great, but it actually means that a BGP peer connection does not yet exist with the prospective neighbor. Before we continue with this example, let's look at the different BGP states:

Idle is the initial state of a BGP connection. The BGP speaker is waiting for a start event, generally either the establishment of a TCP connection or the re-establishment of a previous connection. Once the connection is established, BGP moves to the next state.

Connect is the next state. If the TCP connection completes, BGP will move to the OpenSent stage if the connection does not complete, BGP goes to Active.

Active indicates that the BGP speaker is continuing to create a peer relationship with the remote router. If this is successful, the BGP state goes to OpenSent. You'll occasionally see a BGP connection flap between Active and Connect. This indicates an issue with the physical cable itself, or with the configuration.

OpenSent indicates that the BGP speaker has received an Open message from the peer. BGP will determine whether the peer is in the same AS (iBGP) or a different AS (eBGP) in this state.

In OpenConfirm state, the BGP speaker is waiting for a keepalive message. If one is received, the state moves to Established, and the neighbor relationship is complete. It is in the Established state that update packets are actually exchanged.

So even though the show ip bgp neighbor output indicated that this is an Active neighbor relationship, that's not as good as it sounds. Of course, the reason the peer relationship hasn't been established is that we haven't configured R3 yet!

R3(config)#router bgp 200

R3(config-router)#neighbor remote-as 100

Verify the peer establishment with show ip bgp neighbor:

R3#show ip bgp neighbor

BGP neighbor is, remote AS 100, external link

BGP version 4, remote router ID

BGP state = Established, up for 00:01:18

Last read 00:00:17, hold time is 180, keepalive interval is 60 seconds

Neighbor capabilities:

Route refresh: advertised and received(old & new)

Address family IPv4 Unicast: advertised and received

Received 5 messages, 0 notifications, 0 in queue

Sent 5 messages, 0 notifications, 0 in queue

Route refresh request: received 0, sent 0

Default minimum time between advertisement runs is 30 seconds

Local host:, Local port: 179 (BGP uses TCP Port 179)

Foreign host:, Foreign port: 11007

The peer relationship between R1 and R3 has been established!

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.

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
2006 iEntry, Inc.  All Rights Reserved  Privacy Policy  Legal

archives | advertising info | news headlines | free 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