Wassim

In this short port we explore the possible DTP modes and configure them on a Catalyst switch. We also learn what the outcome would be if we combine them. When configuring the Dynamic Trunking Protocol, Cisco recommends to set trunking as static. But here is the behaviour if we don’t set it to “switchport mode trunk”. For Catalyst 2960 and Catalyst 3560, I found that the default Dynamic Trunking Protocol mode is “dynamic auto”. Key behaviours: Dynamic auto+ dynamic auto = access dynamic auto+ access/trunk = access/trunk Dynamic desirable + access = access Dynamic desirable + else = trunk Default modes Here are a couple of outputs that reveal the default Dynamic Trunking Protocol modes, on Catalyst 2960 and Catalyst 3560: on Catalyst 2960 on a 3560 A combination of the above I’m going to set different DTP modes on both ends of the link, and see the behaviour of DTP on Catalyst switches. I have SW1 and SW0. Dynamic desirable + Access –> Access W...

In this lab, I learned the following: configuring a HSRP group on physical interfaces, testing how a PC can reach a remote subnet through a redundant gateway, by configuring its default gateway as the HSRP virtual address, testing how the second router becomes Active, testing interface tracking. For interface tracking, at first, I thought there was a problem with the lab. Topology: configure interface tracking and a decrement value: When I shut down ser0/0 on R2, I expected R2 to become Standby router. But reality bites: Then I checked on R3. R3 is still Standby, not Active ! So what’s wrong? Here’s what Cisco says: How Object Tracking Affects the Priority of an HSRP Router The priority of a device can change dynamically if it has been configured for object tracking and the object that is being tracked goes down. The tracking process periodically polls the tracked objects and notes any change of value. The changes in the tracked object are communicated to HSRP, either immedi...

I had the opportunity to participate in an official Juniper Networks course titled “Configuring Juniper Networks Routers”, aka CJNR. My boss was kind enough to ask my client to give me five days off. Our instructor was JNCIP certified and works at Twine Networks . All I can say is that 5 days aren’t enough. Juniper Networks should reconsider the necessary time for the CJNR course. There is a lot of knowledge to cover. Labs take a considerable amount of time if you want to assimilate the steps and not only do the secretary work of reading the manual and typing the instructions as shown. For example, we didn’t cover the multicast course as we ran out of time. Topics like BGP, routing policies, multicast and firewall filters on JUNOS sounded like “Chinese English” to me.

import = receive into routing table export = send to neighbors, or, redistribute (or not).OSPF —— Default import policy: accept all OSPF routes from neighbors Default export policy: advertise all direct routes (including loopback interfaces).Here’s an example to illustrate it. Dubai learned the 15.15.15.15/32 route through OSPF from Tokyo. In fact, the default export policy in Tokyo is to advertise its direct routes, one of which is 15.15.15.15/32. The default export policy on Dubai is to export all direct routes. Then MontReal learned 15.15.15.15/32 from Dubai, because the default import policy is to accept any OSPF routes. Wait a minute, 15.15.15.15/32 is not a direct route in Dubai. So how does Dubai advertise it to MontReal? I found the answer to it in JUNOS Enterprise Routing book. It says : “ The default LS export policy is to reject everything. LSA flooding is not affected by export policy, and it is used to convey routing in an indirect manner in an LS pr...

Building a Juniper olive lab and playing with it is no different than gathering Cisco OS images and stuffing them into GNS3 or eve-ng. This articles describes some of my ramblings. As you know, in order to play with Juniper Junos in a lab, you need to configure instances of Olive. In my home lab, I have configured 6 Juniper Olives to play with. This is an overkill for JNCIA and JNCIS. But I got hooked on this topic for a couple of days. I remember waking up and labbing at 4.20 am building Olives LOL. Maybe my motivation behind that is that I wanted to practice every Junos topic on the exam guide as quickly as possible. So here’s the topology of my first Juniper home lab: Candidate Configuration vs Active configuration in Junos Let’s check show configuration interfaces on the operational mode: We have the same output with “show interfaces” under [edit interfaces] level: Let’s make a little change under interface tap (I added a description ): Now, if we issu...

  The setting: two Catalyst switches. On each one of them I created two VLANs. A trunk between both switches is set up. Scenario: I shutdown the trunk port on side A: No more VLANs are detected on the local trunk port: However, side B’s trunk port is still untouched. And it shows a list of allowed VLANs on the trunk, as if nothing special has happened: Conclusion Even if the trunking seems to be OK on one switch, we should check the trunk on both sides of the switches.

Maybe some folks would know how I prepared for the exam. Here’s what I did: I first read Cisco Student Guides (vol1 and 2). At first, it seemed like learning Chinese. OSPF LSA3,4,5, EIGRP SIA, NSSA, BGP,.. I read each chapter at least twice and took notes. I followed a different reading approach. Instead of reading a book from cover to cover, I made what I call a “topic reading”, i.e. I read all the material related to a specific topic together. I felt a little overwhelmed sometimes when I find myself with the same topic for weeks! But it pays on the long run. I do as many labs as I can per topic. I did all the labs on Chris Bryant’s books, almost all labs from Cisco Lab Portfolio and dozens of mini-labs to understand small mechanisms. sometimes I watch video material after reading books, to break routine and boredom. always jot down questions. any question related to networking, not only to BSCI topics. Last days of preparation: Cisco Exam Guide “Do I know...