Uplink Fast
Uplink Fast
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Cisco enhanced the original 802.1D specification with features such as Uplink Fast to speed up the convergence time of a bridged network.
The drawback is that these mechanisms are proprietary and need additional configuration. The UplinkFast feature is a Cisco proprietary technique that reduces the recovery time further down to the order f 1 sec
Normal Scenerio without Uplink fast
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Assume SW1 = Root Bridge
SW3 = access switch with one of its uplinks in blocking mode
Uplink from SW3 to SW2 via port A is primary and SW3 to SW2 via port B is redundant uplink
SW1——————- SW2
– -
– -
– -
– -
-SW3-
suppose uplink SW3 to SW1 fails,port A goes down immediatly.SW3 consider now link to SW2 as its still receiving BPDUs from root,but to get the link to forwrding state ,it will take 30 sec(learning and listening stage) Port B reaches forwarding state after 30 sec qnd network connectivity is established.
Scenerio with Uplink fast
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Note: 1) The switch has only two uplinks.
2) The switch has more than two uplinks, but the STP parameters are set in such way, that Continue reading
What I’ve Been Doing Lately
Beside Cisco and my MBA, I work as managing director for a non-profit organization GEM Foundation that I founded last year along with other Indonesian professionals.
Our focus is to help preparing Indonesian students and young professionals, as the next generation leaders for my country, to be prepared for the global competition.
Our activity includes regular biweekly Webex session by experienced professionals and entrepreneurs, mostly live outside the country, to share their knowledge, wisdom, experience, tips and tricks in finding a job, getting a job, or creating a job.
In average 70-80 students and young professionals attended our session.
We always try to meet the students in person in order to provide inspiration and opportunity to have face-to-face and open discussion. Last year I met more than 400 students and professionals during my visit to 4 universities in Indonesia.
My activity won me spot in national news. But I didn't bother.
Early this month I went to one technical high school and couple of universities in one Indonesian city called Malang, to do something similar like last year. I was given honor to give keynote speech in the annual event arranged by the alumni of the high school.
I Continue reading
CCDE Group Study by INE
Over the weekend I attended the CCDE group study sponsored by INE in Chicago. Discussion and material were let by Petr Lapukhov and Brian McGahan. I’m very excited to see high level networking event in my hometown. We had about 15-20 people in the class. This was my first exposure to CCDE so it was a lot of information absorbing. The test is composed of 4 scenarios. You have about 8 hours to pass the computerized test. Just like in other written Cisco certifications, you can’t go back once you answer the question. The test seems to be based on mastering the design’s information extraction from pages and pages of information. Most of the technology focus is on MPLS, routing, QoS and some security.
In the group study we went through Cisco’s CCDE practice demo (https://learningnetwork.cisco.com/docs/DOC-2438). I thought the discussion was very interested, especially from people that have been studying for the test. If you take it and want to look at the solution you can find it at http://www.shafagh.net/2012/08/ccde-demomystery-solved.html. Next we went through INE’s CCDE practice scenarios written by Petr and Brian.
Mainly, I wanted to post some very interesting documents that Continue reading
Quiz #9 – BGP peering over a Cisco ASA
Your company has 2 offices that are interconnected via a firewall (Cisco ASA) as shown below. You received the task to configure a BGP session between the border routers but something does not go according to plans.
PBR – Policy-based Routing configuration example
How does the internet work - We know what is networking
Policy-Based Routing Configuration Here we will show different examples for configure specific PBR types: Enabling PBR on the Router Fast-Switched PBR Local PBR CEF-Switched PBR Enabling PBR This command will define that the router will use PBR and that the PBR will use route-map named TEST. R1(config)# route-map TEST permit 10 Defines a route map […]
Show 136: Avaya – Considerations for Turning your Network into an Ethernet Fabric – Sponsored
We’ve done a few shows now on Ethernet Fabrics where we have been getting deep into the different technology options and different vendor implementations. Avaya has sponsored this show where we actually interview customers who were early adopters of fabric-based and talk about what drove these customers to implement a network fabric, how they went […]
Author information
The post Show 136: Avaya – Considerations for Turning your Network into an Ethernet Fabric – Sponsored appeared first on Packet Pushers Podcast and was written by Greg Ferro.
Network behind an IPSec VPN peer
In this lab, I tried to simulate an environment where there are two customers, each connected to their respective ISP. Now, in real world, this might not be the best way things are done, but this lab is for the sake of understanding how VPNs deal with networks behind a VPN peer.
PE: Provider Edge equipment
CPE: Customer Premise equipment
Following is the network diagram. CPE1 and CPE2 are customer edge routers. PE1 and PE2 are respective ISP provider edge routers. Each router connects to another over a /30 point to point link. Each router has a loopback (Lo0) with an IP address in the 192.168.0.0/16 range as shown.
CPE1 has a site to site VPN tunnel to PE1.
PE1 has two site to site VPN tunnels, one to CPE1 and another to PE2.
PE2 has two site to site VPN tunnels, one to PE1 and another to CPE2.
CPE2 has a site to site VPN tunnel to PE2.
I had a problem with VPN Hairpinning and wanted to build a lab to find possible solutions. I started off building the lab and after bringing up VPNs, I realized I built the lab wrong. Notice how Continue reading
Default route and RIB/FIB entries
If a router has multiple routes to a network over multiple routing protocols, it stores all routing information in the RIB. This information may not be necessarily used when determining best path to the network. To determine best path to the network, CEF uses the FIB. I understand this.
Consider a network where:
R2 ------- R1 ------- R3
R2 (10.0.0.2/24) connects to R1 (10.0.0.1/24)
R1 (192.168.0.1/24) connects to R3 (192.168.0.2/24)
On R2, R3: I have default routes pointing to R1:
R2: ip route 0.0.0.0 0.0.0.0 10.0.0.1
R3: ip route 0.0.0.0 0.0.0.0 192.168.0.1
Now, from R2, I can ping R3 fine.
R2#ping 192.168.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/39/44 ms
So, I try to see the route entry for 192.168.0.2
R2#sh ip route 192.168.0.2
% Network not in table
I don't see it. So I look at the CEF/FIB.
Recursive Routing with Tunnels – study case: GRE over IPsec
This post represents the solution and explanation for quiz-6. Running dynamic routing protocols over tunnels can result in recursive problems. Read more to understand the problem and some solutions.
A Cloud Without IPv6
As a Data Center junkie, I daily bear witness to the glorious transformations that are taking place all around me with respect to the “next-generation” of data center. Everyone who wants to move their DC to the next level are millions of dollars worth of DC networking gear that is EXTREMELY cutting edge, enabling virtualization and cloud to do things we only dreamed of being able to do mere years ago.A Cloud Without IPv6
As a Data Center junkie, I daily bear witness to the glorious transformations that are taking place all around me with respect to the “next-generation” of data center. Everyone who wants to move their DC to the next level are millions of dollars worth of DC networking gear that is EXTREMELY cutting edge, enabling virtualization and cloud to do things we only dreamed of being able to do mere years ago.Using GNS3 for Switching Labs
For so long, I’ve heard - as have many of you I’m sure - that GNS3, though a GREAT emulator for Cisco IOS software, is not practical for studying anything related to switching. Routing is handled just fine, but because of the proprietary ASICs in Cisco switches, it is not something that can be easily reverse-engineered, thus GNS3 cannot do it. After all, all routing is essentially done in software in GNS3.Using GNS3 for Switching Labs
For so long, I’ve heard - as have many of you I’m sure - that GNS3, though a GREAT emulator for Cisco IOS software, is not practical for studying anything related to switching. Routing is handled just fine, but because of the proprietary ASICs in Cisco switches, it is not something that can be easily reverse-engineered, thus GNS3 cannot do it. After all, all routing is essentially done in software in GNS3.Quiz #8 – MPLS: inside Provider’s Core
You are a network engineer of a company that provides MPLS services to more customers. Your teams tries to increase the redundancy, but instead they receive complaints that connectivity is broken. What's wrong?