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  1. #1001
    Geek Extraordinaire 2,500+ Posts KenB's Avatar
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    Re: Need some advice on learning networking

    Nothing useful to say.

    I just wanted to be the 1,000th post!
    “I think you should treat good friends like a fine wine. That’s why I keep mine locked up in the basement.” - Tim Hawkins

  2. #1002
    Service Manager 5,000+ Posts
    Need some advice on learning networking

    BillyCarpenter's Avatar
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    Re: Need some advice on learning networking

    Quote Originally Posted by KenB View Post
    Nothing useful to say.

    I just wanted to be the 1,000th post!

    You sneaky devil.
    Embrace the process, not the outcome.

  3. #1003
    Retired 10,000+ Posts slimslob's Avatar
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    Re: Need some advice on learning networking

    Quote Originally Posted by KenB View Post
    Nothing useful to say.

    I just wanted to be the 1,000th post!
    You mean reply. You were the 1001st post.

  4. #1004
    Service Manager 5,000+ Posts
    Need some advice on learning networking

    BillyCarpenter's Avatar
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    Re: Need some advice on learning networking

    Quote Originally Posted by BillyCarpenter View Post
    Here's a fun question. Try to answer without using google.


    Does a layer 2 switch have/need a default gateway? Why or why not?



    I forgot about this queston:



    The answer is, yes, a layer 2 switch needs a default gateway. It also needs an IP address...usually configured on VLAN 1.




    The default gateway on a switch has the same function as any gateway configured on a host PC. Without a default gateway, the switch management address (on VLAN 1 in your case, but it could be on any VLAN configured on the switch) cannot send traffic off its network to another network.
    When a host (including the switch management), wants to send a packet to another host, it needs to resolve the layer-3 address (IP, etc.) to the other host's layer-2 address (MAC, etc.) in order to build a layer-2 frame.
    Embrace the process, not the outcome.

  5. #1005
    Service Manager 5,000+ Posts
    Need some advice on learning networking

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    Re: Need some advice on learning networking

    Are y'all ready for me to bore you some more? Here we go....


    Learning to set up an IPSEC VPN really caused me to go down many different paths. I've covered most of them but here's another one: Access Control List


    An Access Control List can be used for many different purposes. One of the main ways it's used is as a filter. We can apply an Access List on an interface of a router and block or deny certain types of traffic: Example TCP, UDP, ICMP. ect. In addition, we can also filter by port number or just about anything.

    When I was setting up the IPSEC VPN, I used an Access List to filter the IP address of both edge routers. In other words, the IPSEC initiation could only be started by the 2 routers on the Access List - any device that wasn't on the Access List will be denied.


    I'm just starting to dig in to this but a WILDCARD MASK is used in conjunction with an Access List in many cases.


    Once I learn more about an Access List, I'll be back to bore you some more.
    Embrace the process, not the outcome.

  6. #1006
    Service Manager 5,000+ Posts
    Need some advice on learning networking

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    Re: Need some advice on learning networking

    I've been jumping around a lot recently because I needed to take a break from the online CCNA course. I've decided to go back to the organized structure of the online CCNA course after letting my brain rest for a while. But before I do......



    ....I want to make one last comment on site-to-site VPN's.


    The online course I'm taking does teach VPN's but I haven't made it that far and I relied a different source to learn it. Well, today I watched about a 45 minute video on VPN's that's part of the CCNA course that I'm taking and they covered some ground that I hadn't thought about.


    For starters, the VPN that I set up in the Packet Tracer Lab is on a very small scale. But what if there's an office in New York that has 20 different networks in the building and we want to set up a VPN to an office in Boston that has 10 different networks?

    Think about that for a minute.


    Sure we can set up a VPN that connects a single network from New York to Boston but we won't be able to communicate with the other networks at all.

    Somehow the New York office needs to learn about all the networks in Boston and vice-versa. But we can't use a dynamic routing protocol because they use multi-casting and IPSEC doesn't support multi-casting. One solution is to use static routes but that's a ton of work to set up.

    There are a few solutions to this problem but that's where I'm gonna leave it as I'm gong back to where I left off on the CCNA course and I left off on OSPF, not VPN's.
    Last edited by BillyCarpenter; 2 Days Ago at 04:45 AM.
    Embrace the process, not the outcome.

  7. #1007
    Service Manager 5,000+ Posts
    Need some advice on learning networking

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    Re: Need some advice on learning networking

    I spent several hours today studying the OSPF routing protocol. There are a few different routing protocols that are used in a production network: EIGRP, RIP, & OSPF.

    OSPF is an open source protocol and it's supported by all of the vendors unlike the other proprietary routing protocols. OSPF is what is most commonly used by far. It's also the most complex to understand and implement.

    One area that I made great progress in was understanding "wildcard masks". Wildcard Masks are used to specify a range of IP addresses and they are always used with OSPF as part of the network statement.





    If you're feeling adventurous, here's how it works:


    Wildcard masks



    Wildcard masks are used to specify a range of network addresses. They are commonly used with routing protocols (like OSPF) and access lists.


    Just like a subnet mask, a wildcard mask is 32 bits long. It acts as an inverted subnet masks, but with wildcard mask, the zero bits indicate that the corresponding bit position must match the same bit position in the IP address. The one bits indicate that the corresponding bit position doesn’t have to match the bit position in the IP address.


    Here is an example of using a wildcard mask to include only the desired interfaces in the OSPF routing process:









    Router R1 has three networks directly connected. To include only the 10.0.1.0 subnet in the OSPF routing process, the following network command can be used:


    R1(config)#router ospf 1
    R1(config-router)#network 10.0.1.0 0.0.0.255 area 0
    Let’s break down the wildcard part of the command. To do that, we need to use binary numbers instead of decimal notation.


    10.0.1.0 = 00001010.00000000.00000001.00000000
    0.0.0.255 = 00000000.0000000.00000000.11111111
    The theory says that the zero bits of the wildcard mask have to match the same position in the IP address. So, let’s write the wildacard mask below the IP address:


    00001010.00000000.00000001.00000000
    00000000.00000000.00000000.11111111
    As you can see from the output above, the last octet doesen’t have to match, because the wildcard mask bits are all ones. The first 24 bits have to match, because of the wildcard mask bits of all zeros. So, in this case, wildcard mask will match all addresses that begins with 10.0.1.X. In our case, only one network will be matched, 10.0.1.0/24.


    What is we want to match both 10.0.0.0/24 and 10.0.1.0/24? Than we will have to use different wildcard mask. We need to use the wildcard mask of 0.0.1.255. Why is that? Well, we again need to write down the addresses in binary:


    00001010.00000000.00000000.00000000 = 10.0.0.0
    00001010.00000000.00000001.00000000 = 10.0.1.0
    00000000.00000000.00000001.11111111 = 0.0.1.255
    From the output above, we can see that only the first 23 bits have to match (notice that the third octet of the wildcard mask has a 1 at the end). That means that all addresses in the range of 10.0.0.0 – 10.0.1.255 will be matched. So, in our case, we have successfully matched both addresses, 10.0.0.0 and 10.0.1.0.


    NOTE
    Wildcard mask of all zeros (0.0.0.0) means that the entire IP address have to match in order for a statement to execute. For example, if we want to match only the IP address of 192.168.0.1, the command used would be 192.168.0.1 0.0.0.0.
    A wildcard mask of all ones (255.255.255.255) means that no bits have to match. This basically means that all addresses will be matched.
    Embrace the process, not the outcome.

  8. #1008
    Service Manager 5,000+ Posts
    Need some advice on learning networking

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    Re: Need some advice on learning networking

    I took about a 2 month break from the CCNA course because I had reached burnout. Anyone that's thinking of getting their CCNA should understand that there's more to it than meets the eye. There's a lot of math that must be learned. I'm not talking about Algebra or Trig, I'm talking about Binary. When I say Binary, I'm talking about subnetting, super netting, route summarization and and converting between binary and decimal. It can and will get tricky. I venture to guess that many students give up because of this. You can't run from it, you must embrace it. And you'll have to learn a new language while you're learning all this math. I'm talking about CLI or Cisco syntax.

    On top of learning all of that, you're also expected to learn a boatload of protocols. Protocols are simply a shitload of rules that were written by the developers of the software that we must learn to follow in order to get anything to work.


    I was sitting here making sure I completely understood a wildcard mask and there was a lot of math involved. Master it or get left behind. That would be my advice.
    Embrace the process, not the outcome.

  9. #1009
    Service Manager 5,000+ Posts
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    Re: Need some advice on learning networking

    PS - The good news is that once you learn all that math, you can really do some amazing things with OSPF. It's an amazing routing protocol, IMHO.
    Embrace the process, not the outcome.

  10. #1010
    Service Manager 5,000+ Posts
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    Re: Need some advice on learning networking

    I've really developed a passion for routers and switches. Maybe that's because things are slowing down for me and I'm on the downside of the learning curve. It's been very rewarding experience thus far. Hard work but rewarding.


    It's rewarding to know that I could set up a network with 200 PC's and segment them by VLAN and then set up inter-vlan routing. How do you want to get inter-vlan connectivity? - by router on a stick or use a layer 3 switch?


    How about getting connectivity between 20 Wide Area Networks? We can do that with a little help from a dynamic routing protocol - OSPF.


    How about setting up an IPSEC VPN? All of that can be done and much, much more.

    Back down to earth. I'm only about 50% done with the CCNA course. Back to the grind.
    Embrace the process, not the outcome.

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