Zakir A. Khan - CCIE

Introducing CCIE# 25121 !!!

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Tue, 11 Aug 2009 08:01:35 -0400

With the blessing of the almighty Allah, I managed to pass the CCIE exam at my first attempt in Sydney, Australia! What a relief. It was a wonderful journey of 9 months of dedicated studying, spending large portion of the time on the Cisco devices, spending thousands of dollar on study materials and lab equipments, many hours of frustration, only 4/5 hours of daily sleep, travelling 16+ hours to the lab location, suffering from the Jet Lag, attending the 8 hours of lab exam and finally a 5 digit number beside my name.

So how it started? I decided to go for the CCIE when I started to work for an ISP here in Canada. But that time I was only CCNA. So I took CCNP, CCIP certifications to build up a good foundation for the CCIE R&S exam. As a part of my CCIE preparation, I went through several books (Doyle, Odom etc.), workbooks (IE), mock labs, Cisco documentation, various forums like groupstudy others. I spent thousands of hours on equipments. I was lucky enough to have my own rack of equipments.

Finally, when I planned to book my lab exam, I was unable to find any seat in USA (as I live in Canada). This is because Cisco recently announced to start the new format of CCIE R&S lab exam from October, 2009. So finding no other ways, I booked my lab in Sydney, Australia. I made a 16+ hours journey to Australia and reached there just before the exam day.

On lab day, I was in the Cisco building about 1 hour before the exam time. There were 4 other candidates... we all were waiting for the proctor to show up. The proctor was late, so our exam started at 9:15. The first 30 minutes was for the OEQ (Open Ended Questions). The OEQ questions were really really easy, very basic questions. No need to give any extra afford for those. Accoring to the proctor, those are marked manually by the proctor, and all they look for is the specific answer, they won't care about any spelling mistake or grammer. I was able to finish the OEQ in 20 minutes and started my lab immediately. I used the first 45 minutes reading the entire lab, making task tracking sheet, adding aliases/some common commands which I often use. After reading the lab it looked like a piece of cake to me comparing to the IE labs. I was able to reach "the golden moment" (full connectivity) before lunch. I was also able to do some non-core tasks before lunch. After lunch it went pretty smooth. I only visited the Cisco documentation site only once for a single task during the lab. When I finished my lab, I still had 2 hours left in my hand. So I fully utilized it by verifing every single task twice. In the whole exam I rebooted my rack twice - 1st time just before lunch and 2nd time at the end of the day.

After the exam I realized I have a good chance to pass it. And it didn't take very long. I got my result within 2 hours of finishing the exam. I was completely speechless to see my certified status along with the 5 digit number.

To tell you the truth, I was completely restless for the last 1.5 years. I used my vacation days either for studing or for the exams. So it's time for me to relax for a bit until I start my 2nd track.

So what's next? I am planning to attend the CCIE Service provider lab this December (after 4 months) as I feel like i am already 70% prepared for it. I also want to start playing with the "Security" track.

Finally, I would like to thank my family, my friends, my colleagues and everyone who helped me directly or indirectly along my first CCIE journey.

The key thing is... if you want something really bad you will get it… Motivaton and patience are the key factors… Always remember: "Winners never Quit & Quitters never win!!"

Understanding Mobile Router/Mobile Network

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sat, 01 Aug 2009 21:53:00 -0400

What does mobile IP do? It allows a mobile router to keep the same IP address while traveling from one network to another and provides IP connectivity to the IP hosts connecting through the mobile router. The hosts behind the mobile router are unaware of this mobility.

Mobile IP has three components:
1. Home agent (HA) - An HA is a router on the home network that maintains an association between the home IP address of the MR and the current care-of address of the MR on the foreign network. HA redirects packets by tunneling them to the MR while it is away from home (in the foreign network).
2. Foreign agent (FA) - An FA is a router on a foreign network that provides a care-of address to the MR. It also detunnels and delivers packets to the MR that were tunneled by the HA.
3. Mobile router (MR) - A mobile router, moves from one network or subnet to another, "hides" the IP roaming from the IP hosts connecting through this mobile router so that the local hosts appear to be directly attached to the home network.

Let's go through a quick example:

Continue reading "Understanding Mobile Router/Mobile Network"

Multicast VLAN Registration (MVR)

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sat, 04 Jul 2009 13:13:33 -0400

In Ethernet networks, sending multicast feed to multiple receivers in multiple VLANs causes the replication of the same multicast traffic for every VLAN resulting over-utilization of the bandwidth. Multicast VLAN Registration (MVR) eliminates this by sending multicast traffic only on the dedicated multicast/source VLAN. Then this multicast/source VLAN feeds all the multicast receivers residing in multiple VLANs.

Here R1 is the multicast source and R2 is the receiver. All devices (including SW1) are running PIM dense mode between them and are using EIGRP for the basic connectivity. MVR has been configured on SW1 with VLAN17 being the multicast/source VLAN for the group 235.1.1.1 which is feeding the receivers on VLAN27 for that multicast group. Let's check the relevant configuration on those devices:

Continue reading "Multicast VLAN Registration (MVR)"

BGP: QPPB (QoS Policy Propagation via BGP)

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Mon, 15 Jun 2009 23:06:16 -0400

In a word, QoS Policy Propagation via BGP (QPPB) allows an ISP to implement different QoS policies for different customers using those customer's BGP routes. Rather than going through the theory, let's go the example straight to clear the concept of QPPB.

Continue reading "BGP: QPPB (QoS Policy Propagation via BGP) "

Catalyst Link-State Tracking

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sat, 13 Jun 2009 11:28:20 -0400

Catalyst 3750/3560 supports "Link-State Tracking". It is a simple and straightforward feature. First, some ports are defined upstream ports and some as downstream ports. Then, if all of the upstream ports go down, all the associated downstream ports are forced into the error-disabled (down) state automatically.

In the following example, if the upstream FastEthernet0/1 interface goes down, the downstream interface FastEthernet0/2 will go into a link down state.

Continue reading "Catalyst Link-State Tracking "

Multicast Equal Cost Multipath (ECMP)

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sat, 30 May 2009 20:07:00 -0400

"ip multicast multipath" allows to load split (not load balance) multicast traffic from different sources for the same multicast group across multiple equal-cost paths. Let's go to the example to make it clear:

Continue reading "Multicast Equal Cost Multipath (ECMP)"

Stacked VLAN (Q-in-Q on a router)

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Fri, 22 May 2009 20:11:32 -0400

A cisco router can be configured to do double tagging (Q-in-Q) on VLANs. Cisco calls it "Stacked VLAN Processing". Per cisco website, "A double-tagged, stacked VLAN frame is terminated or tunneled on an Ethernet subinterface by using the encapsulation dot1q second-dot1q command that specifies the two VLAN ID tags: an outer SP-VLAN ID and an inner CE-VLAN ID". So the command syntax for stacked VLAN is "encapsulation dot1q <outer-vlan-id> second-dot1q <inner-vlan-id>" or "encapsulation dot1q <sp-vlan-id> second-dot1q <ce-vlan-id>".

Ethernet subinterfaces on R1 are configured for the stacked VLAN processing. Here R1 is tagging inner VLANs 10 and 20 with outer VLAN 100 which is preserved all the way upto SW2's dot1q tunnel port (fa0/2). On fa0/2 port SW2 strips the outer VLAN 100 and sends the inner VLANs 10 and 20 to R2. The routers and switches are configured as following:

Continue reading "Stacked VLAN (Q-in-Q on a router)"

What does "filter-autorp" do ?

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Fri, 08 May 2009 22:50:00 -0400

So what is the use of "filter-autorp" option in the "ip multicast boundary" command? Let's explore it with an example:

Here R3 is the multicast source and R2 is the client. R1 is serving as RP the for multicast groups 226.0.0.0/8, 228.0.0.0/8, and 232.0.0.0/5. R1 ia also the mapping agent. Let's check the relevant configuration on those routers:

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BGP: Traffic Engineering for Incoming Traffic

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sat, 25 Apr 2009 19:52:00 -0400

In BGP, there are several ways for an AS to influence the incoming traffic on one link over another. We will explore some of them in this post.

Here AS 65001 (R1) is advertising 2 prefixes 1.1.0.0/24 and 1.1.1.0/24 to AS 65026 over two links. Let's check the BGP table on R2 and R6:

Continue reading "BGP: Traffic Engineering for Incoming Traffic"

Router Tricks: Time Based ACLs + GRE + Backup Interface

nospam@example.com (Zakir A. Khan, CCIE# 25121) — Sun, 22 Mar 2009 20:18:00 -0400

R2 has two upstream links to R1. R2 will use both links (fa0/0 and fa0/1) during the work hours (9AM - 5PM), but will only use the first link (fa0/0) during the non-working hours. It can be easily done by using Embedded Event Manager (EEM) on R2 but we will take an interesting different approach. Here it goes...

Continue reading "Router Tricks: Time Based ACLs + GRE + Backup Interface"