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  • 1.  DHCP assigned dynamic IP address for vlan is not routing to other vlans and internet

    Posted 10-15-2024 06:52

    I have a strange problem on a brand new EX4100 switch that I need help on.   

    The brief overview is that if I configure manually a static IP address on the workstation1, it can ping its own vlan gateway, other vlan gateway, and can access the internet.  But if the workstation1 receive a dynamic IP address from the vlan DHCP server, it can only ping its own vlan gateway, but not any other gateway and cannot access the internet.

    The details are as follows.

    I have setup 2 vlans segment with irb in a brand new EX4100 switch.

    Workstation1 connected to vlan10 with IP address 192.168.10.10/24, gateway 192.168.10.1, dns=8.8.8.8.  It can ping to Workstation2, and can access the internet via static route to 192.168.100.1 (firewall port connected to port ge-0/0/23).  The IP address at this stage is manually coded in the network adapter.

    Workstation2 connected to vlan20 with IP address 192.168.20.10/24, gateway 192.168.20.1, dns=8.8.8.8.  It can ping to Workstation1, and can access the internet via static route to 192.168.100.1 (firewall port connected to port ge-0/0/23).  The IP address at this stage is manually coded in the network adapter.

    So the basic foundation is working properly.  Traffic can be routed between vlans, and can go out to internet and I am happy with the switch.

    Now I add a DHCP service to vlan10 to assign IP address 192.168.10.20-25/24, gateway=192.168.10.1, dns=8.8.8.8. and workstation1 is assign 192.168.10.20/24, gateway 192.168.10.1 and DNS 8.8.8.8.  workstation1 can only ping to its own gateway192.168.10.1 and cannot reach out to other vlans gateway, cannot ping worksation2 and cannot go out to internet.

    Now I add a DHCP service to vlan20 to assign IP address 192.168.20.20-25/24, gateway=192.168.20.1, dns=8.8.8.8. and workstation2 is assign 192.168.20.20/24, gateway 192.168.20.1 and DNS 8.8.8.8.  workstation2 can only ping to its own gateway192.168.20.1 and cannot reach out to other vlans gateway, cannot ping worksation1 and cannot go out to internet.

    In short, if the IP address is assigned by the DHCP server, the workstation cannot access anything outside its own segment.  But if it is manually coded in the network adapter in windows 10/11, the workstation will work fine.  And there is no change to the IP address, mask, gateway, dns.  The same is used for static and dynamic assigned IP address.  So this is a very strange problem to encounter.

    I have also upgraded the switch JunOS to 22.4R3, 23.2R1 and 23.4R2.  It has the same problem across this JunOS.

    Please help me take a look at this problem urgently.  Thank you





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    STEVEN CHAN
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  • 2.  RE: DHCP assigned dynamic IP address for vlan is not routing to other vlans and internet

    Posted 10-29-2024 22:37

    Hi Steven,

    Is the DHCP scope and configuration on the EX4100? If yes, can you kindly share the DHCP configuration? Also, the output of "show dhcp server binding detail" as well.

    Regards



    ------------------------------
    Sheetanshu Shekhar
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    Original Message


  • 3.  RE: DHCP assigned dynamic IP address for vlan is not routing to other vlans and internet

    Posted 10-31-2024 09:47
    Hi Support,

    This support case status is currently resolved.  After much troubleshooting with your colleague from Juniper support, over tracing the traffic package and wireshark etc, we finally went through the physical configuration statements in the switch configuration.  We then discovered that there is typo error on the router IP address.  No wonder, that's why the workstation cannot access the internet after the IP address was assigned by the DHCP service.  Incidentally, the configuration for 1st dhcp service was copied into 2nd and 3rd dhcp service configuration for the 2nd and 3rd irb subnet, thus the error was repeated for all 3 irb subnet.  This gives the impression that there is something wrong with the switch, but the error is due to a human error.  The workstation works flawlessly (able to access the internet) with a DHCP assigned IP address after the router address was corrected.

    The problem is already resolved.  Please kindly close this support case.

    Thanks for following up.


    Regards
    Steven Chan
    Senior Consultant

      
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    Original Message