Changed netmask to /20 and now no internet



  • Hello,
    I changed the netmask from 24 to 20 so this gives me range from 192.168.0.0 to 192.168.15.254.  My DHCP lease is 192.168.1.120 to 192.168.1.250 and anything outside of that (ie:192.168.1.1 to 192.168.1.119) is static IP. If I assign a computer with static IP of 192.168.3.9, subnet mask: 255.255.240.0, gateway: 192.168.1.1. I cannot access the internet, I am able to ping other systems like my desktop for example (192.168.1.10), but I cannot ping 192.168.3.9 from my desktop. What am I doing wrong?

    any help will be greatly appreciated.

    Thank you



  • IMO, a broadcast domain with over 4k hosts is doing it wrong. Aside from that, did you make sure it was changed everywhere- LAN interface, AON rules, etc? You need to have the same netmask on all the thousands of devices you have on your network- the firewall, all the hosts… You do have thousands of devices, right?



  • Well not really thousands… but hitting close to 800 right now... about 200 computers and adding another 100 in a next couple of months, and rest are bunch of different networked devices, like data loggers, IP phones etc.
    I would be OK with /22 but i think I would run into same issues as /20.

    Yes the netmask is updated everywhere


  • Netgate

    You have to change the netmask on all of the devices too.

    Either a release/renew, reboot, reconfiguration of static, etc.

    As an aside, I agree that some segmentation is probably in order.



  • like VLANs?



  • like data loggers, IP phones etc.

    In larger networks, IP phones are generally put on a separate VLAN.  In addition to reducing the broadcasts on the main network, it also allows for giving priority to VoIP traffic.


  • Netgate

    @zer0:

    like VLANs?

    Separate broadcast domains.

    If you choose to use VLANs that would work.



  • Is it possible to perform administrative tasks on separate VLANs from one computer? for example, VLAN 101 = Computers, 102 = data loggers, VLAN 103 = IP phones. If i wanted to manage data loggers or IP phones, would I need to make my computer part of that VLAN in order to access them?



  • @Derelict:

    @zer0:

    like VLANs?

    Separate broadcast domains.

    If you choose to use VLANs that would work.

    Just to clarify, with VLANs, the traffic is still on the wire, but not bothering as many devices.

    The problem with broadcasts is that all devices have to receive and process them, whether they're interested or not.  Broadcasts are used for a lot of things, including ARP, initial DHCP requests, Windows networking and more.  The trend is to use multicasts, which target selected groups of devices, so others don't have to handle them.  On IPv6, there are no broadcasts, only multicasts and most multicasts only go to the desired groups, down to a single device.  The closest thing to a broadcast on IPv6 is the all hosts multicast and those are used only for things like router advertisements that have to go to all devices.

    With VLANs, the traffic is split into logically separate networks, for example the VoIP phones I mentioned in another message.  It could also be split according to departments or function, for added security.  Whatever the reason, VLANs reduce the size of "broadcast domains" and the amount of processing wasted on handling unwanted broadcasts.

    Bottom line, it is possible to have a network with a large number of devices on it, but that means every device has to handle all those broadcasts, rather than just a portion of them.



  • @zer0:

    Is it possible to perform administrative tasks on separate VLANs from one computer? for example, VLAN 101 = Computers, 102 = data loggers, VLAN 103 = IP phones. If i wanted to manage data loggers or IP phones, would I need to make my computer part of that VLAN in order to access them?

    Yes, while it's possible to have multiple VLANs on a single computer, the VLANs can normally be reached through a router, just as though they were separate networks.


  • Rebel Alliance Global Moderator

    JKnott - I have to say I was waiting for you to say you could just run all the same vlans on the same dumb switch.. I am very happy with your last response ;)

    To the OP.. Why are you wanting to use a /20?  As already mentioned you should be looking to segment your different devices.. not put them all on the same network..

    What you should do is sit down and think about the different sorts of devices on your network.. Printers, servers, clients be it desktops, wireless tablets phones, etc. etc..  And then put the different devices/users you want to be able to isolate from each other on their own vlans… Then using pfsense you can easy firewall between these vlans.

    If you give us some details we can help you try org your network better.. Vs you just growing larger and larger flat network..  What happens when you get over 4k devices.. Do you then move to a /19?



  • JKnott - I have to say I was waiting for you to say you could just run all the same vlans on the same dumb switch.

    You still can on a small network, but there's no way I'd recommend it for a large one.  In my own network, my original intent was to have a guest WiFi, with it's own SSID/VLAN.  However, as discussed elsewhere, my TP-Link AP wasn't up to the task.  In this situation, a performance hit caused by a lot of broadcasts was not a concern, only separating the guest network from the regular one and it wasn't worth buying a managed switch just for that task.



  • @johnpoz:

    If you give us some details we can help you try org your network better.. Vs you just growing larger and larger flat network..  What happens when you get over 4k devices.. Do you then move to a /19?

    Thank you guys!. I have sketched a network diagram as it stands today…. basically all switches are acting as dumb switches at the moment. When we started small we just kept adding switches and plugging things into open ports.

    Any advice on how i should organise this would be greatly appreciated.

    Please see attached.

    ![LAN network2.jpg](/public/imported_attachments/1/LAN network2.jpg)
    ![LAN network2.jpg_thumb](/public/imported_attachments/1/LAN network2.jpg_thumb)



  • When we started small we just kept adding switches and plugging things into open ports.

    A suggestion, instead of chaining switches in that manner, choose one to be the root switch and connect the other switches to it.


  • Rebel Alliance Global Moderator

    What are the make of these managed switches and what port density?  Your going to need to get rid of those dumb switches unless you can leverage them all on the same network for all devices plugged into them.

    What is the physical layout?  Where are these switches.  Do they sit in IDFs, or they all in the MDF or are they sitting under some guys desk?

    And you have more dumb switches downstream.. Just caught that.. Wow sounds like a real mess… You have your phones running on the same broadcast domains as all your other users and computers.. Same as your wifi network even?  you do understand all your broadcast traffic is going out over your wifi network right... And its shared bandwidth... So yeah lots of noise on your wifi for no reason.

    That is part of the reason you don't just connect your wifi to a /20 ;)



  • I agree it is a cluster f#@k of things.
    I have 3x Linksys SRW2048 (48 ports, I knows its old but works for me), 2x Cisco Catalyst 3750G (24 port each), 1x HP Procurve 1800-24G, 1x SMC GS24C SMRT ( I mean SMART). 3x 24 port dumb switches.
    The downstream switches are used for connecting 8 computers/phones to single CAT5E/CAT6 cable which is coming from the server room.
    All the managed switches are sitting in the same room mounted on couple different racks.


  • Netgate

    If that is actually a representation of how you have those physically connected the first thing I would do is take one of the better managed switches and use it as a "core" switch and run out to each switch individually. In other words, don't daisy-chain switches since one failure takes down everything downstream of that.

    In order to segment that network you will either need to:

    1. Be satisfied with "geographic" segmentation with a different VLAN going to each edge switch untagged.

    2. Get managed switches everywhere.

    ETA: Missed JKnott's reply up there. Looks like there is agreement regarding the physical topology. :)



  • The downstream switches are used for connecting 8 computers/phones to single CAT5E/CAT6 cable which is coming from the server room.

    I came across something like that recently.  I was installing VoIP phones in an office.  There was a PoE switch, so it should be a simple matter to unplug the cable from a computer and plug it into the phone.  Yeah, right.  I often found a small switch hidden somewhere connecting multiple computers to 1 PoE port, which makes it impossible to power more than 1 phone.  Use of those small switches in a business environment should be discouraged, given the problems they might cause.  On that job, I even came across one switch where a cable was held in place by an elastic band, because the latch tab was broken off!



  • Lets look at 1 part of this entire network, if you can help me organise this, I think I can apply the same logic to rest of the network. Please see the picture attached,
    There is 1 CAT5e cable in the room that is coming from the secondary switch PORT#1 , it terminates into a switch in the room in Port#2, rest of the ports on the switch in the room are connected to IP phones, Desktop computers, and photocopier/printer/scanner. All Desktops and Printer/scanner needs access to File Server and the VMs. IP phones only need to access the PBX VM.

    How would you organise this network? Also which of the switches do you think should be the "CORE" switch? I also have Extreme Networks C5K175-24, which I forgot to mention above, its just sitting around.

    Thank you

    ![LAN network_v2.jpg](/public/imported_attachments/1/LAN network_v2.jpg)
    ![LAN network_v2.jpg_thumb](/public/imported_attachments/1/LAN network_v2.jpg_thumb)



  • Also which of the switches do you think should be the "CORE" switch?

    That would depend on the switches you have.  I don't know how they compare, but generally you'd put the one with the best performance, e.g. 1 Gb vs 100 Mb as core.  You mentioned dumb switches, those would probably be best for connecting computers, etc. to.  Are some PoE?  Use them for phones.  VLANs will require managed switches.  These are the sorts of things to consider.  Regardless, ensure you set it up in a tree structure, with a "root" switch and other switches as branches.  Also, make sure you don't create loops, unless you're certain all the switches support spanning tree.


  • Netgate

    Also which of the switches do you think should be the "CORE" switch?

    Certainly nothing wrong with a 3750G, other than being kind of old but who cares right? I have no experience with the rest.

    But, honestly, if you are OK with a flat network that couldn't be firewalled in the first place, a layer 3 switch makes more sense. That way "closet" to "closet" traffic doesn't have to go through the firewall.

    You will need to be careful regarding any apps/workflows that rely on broadcasts for discovery, etc.



  • Just curious if there is another way to reduce broadcast noise other than VLANs?

    Thanx


  • Rebel Alliance Global Moderator

    Tell your clients to do less broadcasts ;)  Windows loves broadcasting and multicasts.. Noise creation monsters…

    And out of the box not only does it do it for ipv4 it does it on ipv6 as well - so even more noise.. With some tweaking you can reduces some of the noise it puts out..

    On your managed switches you can block say the multicast stuff if your not using it at the switch levels - so it won't go past where your managed switches are..



  • Just curious if there is another way to reduce broadcast noise other than VLANs?

    Turn off the radio.  ;)

    Move entirely to IPv6.  There'll be absolutely no broadcasts then.  IPv6 relies on multicasts, where the closest thing to a broadcast is an all hosts multicast.  Beyond that, multicasts are only received by the intended audience and in one case, solicited node multicast, only one device will receive it. Well, not exactly true.  There's a 1 in a more than 16 million, 2^24 chance that an unintended device will receive it.  As I mentioned earlier, the problem with broadcasts is not time on the wire, but that every device has to process them, whether wanted or not.  Multicasts greatly reduce or even eliminate that issue.  Beyond that, VLANs are what you need.



  • @JKnott:

    Just curious if there is another way to reduce broadcast noise other than VLANs?

    Turn off the radio.  ;)

    Move entirely to IPv6.  ….

    Yeah ! I just tried that, deactivating the IPv4 in the Network card's properties ….
    Half of the devices on my local network, well, vanished (those without a dual stack) !

    But, it works : I'm posting this reply using IPv6 only :)

    Sorry for the out-of-subject.


  • Rebel Alliance Global Moderator

    "But, it works : I'm posting this reply using IPv6 only"

    Thats fantastic… Now go to any the about a bajillion websites that are not ipv6 ;)

    www.slashdot.org for example ;)



  • @johnpoz:

    "But, it works : I'm posting this reply using IPv6 only"

    Thats fantastic… Now go to any the about a bajillion websites that are not ipv6 ;)

    www.slashdot.org for example ;)

    My cell phone is IPv6 only.  It uses 464XLAT to access IPv4 only sites.  Some ISPs are doing the same for regular Internet access.  Others, such as Comcast, are moving customers to IPv6, providing IPv4 via carrier grade NAT & 4in6 tunnel.

    I use a browser add-in called "showip", which displays the web site address.  I'm seeing more & more sites with IPv6 addresses, including most of the biggies such as Google, Youtube, Wikipedia, Yahoo and many more.  Also, anyone running Windows HomeGroup networks is using IPv6.  The main things holding back IPv6 are ignorance and inertia.


  • Rebel Alliance Global Moderator

    I agree many sites are ipv6.. And ok sure some services like t-mobile do a gateway to ipv4 address..

    Does his isp do that?  So you plan for him to go full IPv6 does his phones support that.. Do his printers, do all the other devices on his network support ipv6 only?

    Your the ipv6 is better than sliced bread guy around here - are you running your network as only ipv6?



  • Your the ipv6 is better than sliced bread guy around here - are you running your network as only ipv6?

    I'm running dual stack.  However, it is entirely possible to run IPv6 only, provided you have a mechanism, such as described, to provided IPv4 when absolutely needed.  Certainly things like local servers can be run entirely on IPv6.  I have a couple of computers here and traffic between them is always IPv6, unless I specify IPv4.

    And yes, IPv6 brings a lot of improvements, not just no broadcasts.



  • @zer0:

    Lets look at 1 part of this entire network, if you can help me organise this, I think I can apply the same logic to rest of the network. Please see the picture attached,
    There is 1 CAT5e cable in the room that is coming from the secondary switch PORT#1 , it terminates into a switch in the room in Port#2, rest of the ports on the switch in the room are connected to IP phones, Desktop computers, and photocopier/printer/scanner. All Desktops and Printer/scanner needs access to File Server and the VMs. IP phones only need to access the PBX VM.

    How would you organise this network? Also which of the switches do you think should be the "CORE" switch? I also have Extreme Networks C5K175-24, which I forgot to mention above, its just sitting around.

    Thank you

    I've never implemented VLANs :-[ so I wanted to run this through this scenario if you don't mind.

    Pfsense –------Core Switch------Secondary Switch (port#1)--------------------Room switch (port#2)

    Room Switch (port#3)----------- Desktop1
    Room Switch (Port#4)----------- Desktop2
    Room Switch (port#5)-----------IP Phone
    Room Switch (port#6)-----------Printer

    This is how it works in my head, please feel free to correct me
    Steps:
    1. Create 3 VLANs on the LAN interface in pfSense (101=Desktop, 102= IP Phones, 103=Printers)
    2. Configure Core Switch port where pfSense is plugged in as well as secondary switch port as "Trunk"
    3. Configure Port#1 on Secondary Switch as "Trunk"
    4. Configure Room Switch Port#2 as "Trunk"
    5. Room Switch Port#3 and 4 assign to VLAN ID 101 (for Desktop)
    6. Room Switch Port#5 assign to VLAN ID 102 (IP Phones)
    7. Room Switch Port#6 assign to VLAN ID 103 (Printers)

    is that all that is required to put them on separated VLANs?
    Any traffic between desktops and printers can be controlled from pfSense.

    Thank you



  • Why are the printers on a separate VLAN from the desktop?  Since they'll generally be used by the desktop systems, there's not much point in keeping them separate.  Also, since you're using VLANs, you don't need separate ports for computers and phones.  Common practice is to pass the computer connection through the phone.  The phone is configured for it's VLAN and the computer, the native LAN.  This requires the switch port to be configured as a trunk port with the native LAN and phone VLAN on it.  However, if you're using Cisco phones with a Cisco switch, you'd just configure an access port and use CDP to detect the phone and connect the appropriate VLAN to it.


  • Rebel Alliance Global Moderator

    Printers are almost ALWAYS on their own vlan.. For starters in any secure enterprise desktops are on a private vlan and can not talk to each other.  So putting printers on such a vlan would prevent users from printing to them ;)

    Putting them on their own vlan also normally limits the printer servers as the only things that can talk to the printer - this prevents users from directly printing to the printers and bypass any accounting or security print features that might be enabled via server, etc.



  • Well this next week is excellent time for me to mess with my network as most of the staff is on holidays and whatever staff is here, they will be "hardly" working. I'll try out VLANs on a portion of the network and see if i make it better or screw it up more. Ill post updates.

    Thank you everyone for their help.