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EBGP Peering Not Established over a Default Route
This post represents the solution and explanation for quiz-4. The quiz shows that, although the BGP speakers can reach each other, they do not establish an eBGP session. Read more to understand the problem.
Quiz #5 – OSPFv3 Default Route into a NSSA Area
Your company's network consist of a CORE block running OSPF Area 0 and multiple buildings with 2x distribution switches per building running OSPF NSSA areas.
You have asked your junior colleague to configure OSPFv3 (for IPv6) to match the same design as OSPFv2 (for IPv4), but something goes awfully wrong.
NAT – Port Forwarding in Both Directions
This post represents the solution and explanation for quiz-3.
NAT on Cisco IOS can be pretty frustrating sometimes and it may take time and practice to master it.
Quiz #4 – BGP over ISP
Your company has more offices and each of them has a separate internet connection. The default route for each office points towards the ISP. Also, within each office you run iBGP using private AS numbers. You try to establish a BGP session between two offices, but the BGP does not come up. Why ?
Quiz #3 – NAT port redirection from inside to outside
As a network administrator, you've been requested to allow the internal clients to connect to a partner server 3.3.3.3 on port 12345. Unfortunately, you discover that your ISP blocks traffic on that TCP port 12345 and allows only some well-known ports, including 8080. How do you implement this ?
OSPF – Redistribution between different ospf processes
This post represents the solution and explanation for quiz-2.
It shows one of the common problems, solutions and recommendations when implementing MSTP.
MSTP – Inside a Region
This post represents the solution and explanation for quiz-1.
It shows one of the common problems, solutions and recommendations when implementing MSTP.
Quiz #2 – OSPF Redistribution between different processes
Redistribution between different or same routing protocols can become a nasty thing when there are 2 or more redistribution points.
In this quiz, redistribution is configured between 2 different OSPF processes on 2 routers. Without a proper configuration, this can lead to routing loops. Read the quiz to see the loop in action and try to solve it.
Quiz #1 – MSTP
This is my first quiz and I chose an MSTP misconfiguration scenario that could be easily overlooked on the first encounter.
A fiber got cut revealed some hidden MSTP implementation problems. It was enough for one link to go down and the connectivity got impacted in a network that was supposed to be redundant. Read along and try to spot the problem.
Auto-RP and usage of "ip pim autorp listener"
After reading several forums with people arguing about what routers should be configured with the "ip pim autorp listener" command, I have decided to write this post explaining things in my own way (of course, with a lot of pictures, as usual).
ACLs Supported on 3560&3750 Switches– Part II (VLAN Maps)
On 3560 and 3750 series switches, there are several ACL types that can be used, each with its own features and restrictions. This post represents the second part covering VLAN maps.
ACLs Supported on 3560 & 3750 Switches – Part I (Port ACL & Router ACL)
On 3560 and 3750 series switches, there are several ACL types that can be used, each with its own features and restrictions. This post represents the first part covering Port ACLs and Router ACLs.
OSPF on CE-PE links
A pretty long post that summarizes the characteristics of OSPF protocol when using it on a CE-PE link. Read along to review its features, learn about BGP extended communities and loop prevention mechanisms for OSPF on CE-PE links.
Difference for PORTFAST & BPDUFILTER used globally or at interface-level
Portfast + bpdufilter (used together) can be enabled globally or at interface level.
Although the first impression is that the only difference is the global or per-interface effect, this is not entirely true and another subtle and important difference is described in this post.
Matching packets based on their size
Welcome on my very first post on my new fresh technical blog!
This post shows different ways of how to match packets based on their length. While this may not be very common in real production, you will find it useful during your CCIE preparations.