Troubleshooting Layer 2 Ethernet Problem: Loop, Broadcast, Security
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The document outlines a webinar conducted by GLC Networks on troubleshooting Layer 2 Ethernet issues, offering insights into Ethernet technologies, common network problems, and practical solutions. It features an introduction to GLC Networks, presenter qualifications, and a detailed agenda covering key concepts and real-world applications. Participants are encouraged to engage in live practice and Q&A sessions, fostering collaborative learning and networking opportunities.
Troubleshooting Layer 2 Ethernet Problem: Loop, Broadcast, Security
- 1. www.glcnetworks.com Troubleshooting Layer 2 ethernet problem: loop, broadcast, security GLC Webinar, 11 nov 2021 Achmad Mardiansyah achmad@glcnetworks.com GLC Networks, Indonesia 1 Source: mikrotik.com
- 2. www.glcnetworks.com Agenda ● Introduction ● Review prerequisite knowledge ● Ethernet technologies ● Ethernet issues ● Live practice ● Q & A 2
- 4. www.glcnetworks.com What is GLC? ● Garda Lintas Cakrawala (www.glcnetworks.com) ● Based in Bandung, Indonesia ● Areas: Training, IT Consulting ● Certified partner for: Mikrotik, Ubiquity, Linux foundation ● Product: GLC radius manager ● Regular event 4
- 5. www.glcnetworks.com Trainer Introduction ● Name: Achmad Mardiansyah ● Base: bandung, Indonesia ● Linux user since 1999, mikrotik user since 2007, UBNT 2011 ● Mikrotik Certified Trainer (MTCNA/RE/WE/UME/INE/TCE/IPv6) ● Mikrotik/Linux Certified Consultant ● Website contributor: achmadjournal.com, mikrotik.tips, asysadmin.tips ● More info: http://au.linkedin.com/in/achmadmardiansyah 5
- 6. www.glcnetworks.com Past experience 6 ● 2021 (Congo DRC, Malaysia): network support, radius/billing integration ● 2020 (Congo DRC, Malaysia): IOT integration, network automation ● 2019, Congo (DRC): build a wireless ISP from ground-up ● 2018, Malaysia: network revamp, develop billing solution and integration, setup dynamic routing ● 2017, Libya (north africa): remote wireless migration for a new Wireless ISP ● 2016, United Kingdom: workshop for wireless ISP, migrating a bridged to routed network
- 7. www.glcnetworks.com About GLC webinar? ● First webinar: january 1, 2010 (title: tahun baru bersama solaris - new year with solaris OS) ● As a sharing event with various topics: linux, networking, wireless, database, programming, etc ● Regular schedule ● Irregular schedule: as needed ● Checking schedule: http://www.glcnetworks.com/schedule ● You are invited to be a presenter ○ No need to be an expert ○ This is a forum for sharing: knowledge, experiences, information 7
- 8. www.glcnetworks.com Please introduce yourself ● Your name ● Your company/university? ● Your networking experience? ● Your mikrotik experience? ● Your expectation from this course? 8
- 9. www.glcnetworks.com Prerequisite ● This presentation some prerequisite knowledge ● We assume you already understand: ○ How browsing works ○ Computer networks 9
- 11. www.glcnetworks.com Your ISP and you ● ISP is an organisation that is part of internet that provides connectivity to their customers ○ Identified by their AS (Autonomous System) number ○ Identified by their IP address block ● When you connect to internet, you will use your ISP’s address 11 Your ISP. and you are part of them other ISP other ISP google facebook
- 12. www.glcnetworks.com At your ISP (physical connection) 12 Border router Other ISP Other ISP Access router Access router customer customer customer Access network: GPON, WLAN, FO, GSM, ethernet, etc
- 13. www.glcnetworks.com 7 OSI layer & protocol 13 ● OSI layer Is a conceptual model from ISO (International Standard Organization) for project OSI (Open System Interconnection) ● When you send a message with a courier, you need to add more info to get your message arrived at the destination (This process is called encapsulation) ● What is protocol ○ Is a set of rules for communication ○ Available on each layer ● Communication consist of series encapsulation ○ SDU: service data unit (before PDU) ○ PDU: protocol data unit (after header is added)
- 15. www.glcnetworks.com Layered model (TCP/IP vs ISO) and encapsulation 15 / datagram
- 16. www.glcnetworks.com Layer 4 header (which one is TCP?) 16
- 17. www.glcnetworks.com Layer 3 header (which one is IPv4?) 17
- 18. www.glcnetworks.com Ethernet header (which is the MTU?) 18
- 20. www.glcnetworks.com Did you notice? ● There is a big overhead on encapsulation process ● More encapsulation means less payload? 20
- 22. www.glcnetworks.com Ethernet specs ● Defined by IEEE 802.3 ● Media: ○ Coaxial cable ○ Twisted pair ○ Fiber optic ● Devices required: ○ Bridge / switch ○ HUB ● Everyone likes it!! ○ Affordable ○ Easy to install ○ Easy maintenance 22
- 23. www.glcnetworks.com How ethernet works (CSMA/CD) ● Carrier Sense Multiple Access / Collision Detection (CSMA/CD) ○ Every host do not know when other send data ○ Before sending data, host check the shared medium ○ Every host only knows when collision happens ● You will have: ○ Collision domain ■ Area where collision happens ■ Can use any frame ○ Broadcast domain ■ Area when broadcast happens ■ Using broadcast frame ● CSMA/CD != CSMA/CA 23
- 24. www.glcnetworks.com How ethernet works (ARP) ● Address resolution protocol (ARP) ● Bridging between IPv4 and MAC address ● Requires broadcast frame ● Will be eliminated in IPv6 24 Source: ipcisco.com
- 28. www.glcnetworks.com Collision domain ● Area where collision happens ● Some ideas: ○ Using switched network 28 Source: devto.com
- 29. www.glcnetworks.com Broadcast domain ● An area where broadcast happens ● Try use 5-4-3-2-1 rules ● Some ideas: ○ Using router to split segments ○ Port isolation on switch 29
- 30. www.glcnetworks.com Loop ● A condition when frame is forwarded in the media ● Will stop until one of cable is removed ● Some ideas: ○ Do not use traditional switch ○ activate STP between switch ○ Port isolation 30
- 31. www.glcnetworks.com Security ● Apply security on network ● Authentication ● Authorization ● Accounting ● Ideas: ○ Dot1x ○ Captive portal ○ MAC address authentication ○ Prevent rogue DHCP server 31
- 33. www.glcnetworks.com Troubleshooting ● Approach: bottom-up (OSI layer) ● Layer 1 ○ Check cabling: crimping/splicing quality, all pins are OK ● Layer 2 ○ Check looping, collision, broadcast ● Layer 3 ○ Check reachability: ping ○ Check path: traceroute ● Layer 4: ○ Check port reachability ● Layer 5-6-7 (app) ○ Check application message 33
- 34. www.glcnetworks.com How mikrotik can help (1) ● Check statistics on RouterOS ● Cable test ● Duplex mismatch ● Speed flapping ● 34 06:01:47 interface,info ether3 link down 06:01:50 interface,info ether3 link up (speed 100M, full duplex) 06:02:08 interface,info ether3 link down 06:02:10 interface,info ether3 link up (speed 10M, half duplex) 06:03:03 interface,info ether3 link down 06:03:06 interface,info ether3 link up (speed 100M, full duplex) 06:03:23 interface,info ether3 link down 06:03:25 interface,info ether3 link up (speed 10M, half duplex) 06:03:30 interface,info ether3 link down 06:03:32 interface,info ether3 link up (speed 100M, full duplex) 06:03:50 interface,info ether3 link down 06:03:52 interface,info ether3 link up (speed 10M, half duplex) 06:04:59 interface,info ether3 link down 06:05:01 interface,info ether3 link up (speed 100M, full duplex) 06:05:19 interface,info ether3 link down 06:05:21 interface,info ether3 link up (speed 10M, half duplex)
- 35. www.glcnetworks.com How mikrotik can help (2) ● Flow control ● Loop protect ● Check Log ● Graphing ● ● 35
- 37. www.glcnetworks.com preparation ● SSH client ● SSH parameters ○ SSH address ○ SSH port ○ SSH username ○ SSH password 37
- 39. www.glcnetworks.com Interested? Just come to our training... ● Topics are arranged in systematic and logical way ● You will learn from experienced teacher ● Not only learn the materials, but also sharing experiences, best-practices, and networking 39
- 40. www.glcnetworks.com End of slides ● Thank you for your attention ● Please submit your feedback: http://bit.ly/glcfeedback ● Find our further event on our website : https://www.glcnetworks.com/en/ ● Like our facebook page: https://www.facebook.com/glcnetworks ● Slide: https://www.slideshare.net/glcnetworks/ ● Discord (bahasa indonesia): (https://discord.gg/6MZ3KUHHBX) ● Recording (youtube): https://www.youtube.com/c/GLCNetworks ● Stay tune with our schedule ● Any questions? 40