In this video, Todd Lammle continues with his insightful discussion on Variable-Length Subnet Masking (VLSM), plus how to determine the block size for each network within a network design and then apply just the right amount of host bits for each subnet.
- [Voiceover] Now that we understand what VLSM is,…or Variable Length Subnet Mask,…we understand that VLSM can use different masks…on different segments in the network by assigning…different length masks on our router interface.…This is referred to as classless or classless routing…and it's based on the number of hosts on that segment.…For example, looking at this graphic here,…we can see that on my point to point links here…between routers that I have a slash 30.…It doesn't matter that it's a Class A here,…we need to look at the mask.…A slash 30 is a 255.255.255.252.…
This give me a block size of four…in the fourth octet…with only two valid hosts.…Right?…So 10.1.1.8, subnet eight.…My valid hosts are .9 and .10.…And this one here with a slash 30,…block size of four,…subnet is 12.…My valid hosts .13 and .14 with my broadcast address .15.…On this one here we have a slash 28.…Again, it doesn't matter that it's Class A,…it's where am I subnetting in the fourth octet.…This is a 255.255.255.240 which is our…(chuckles) entire block size 16, isn't it?…
For more information on the CCENT exam, visit Cisco's website.
- Overview of internetworking
- The TCP/IP networking model
- Easy subnetting
- Managing Cisco IOS
- Managing Cisco networks and devices
- IP routing
- Layer 2 switching
- VLANs and InterVLAN routing
- Network address translation
Skill Level Intermediate
Internetworking devices4m 20s
3. Introduction to TCP/IP
4. Easy Subnetting
5. VLSM, Summarization, and Troubleshooting TCP/IP
6. Cisco Internetworking Operating System (IOS)
7. Managing a Cisco Internetwork
8. IP Routing
9. Layer 2 Switching
10. VLANs and InterVLAN Routing (IVR)
12. Network Address Translation (NAT)
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