GS1200 DHCP Client and Mikrotik Issue

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  • andyvolk
    andyvolk Posts: 11
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    @Zyxel_Melen, Here are screenshots:

    Green rectangle - is Zyxel which work OK renew ip address.
    Red rectangle - Zyxels which haven't ip address.
    Marked rows - is Zyxels

    Second screenshot is same zyxel from green rectangle at first screenshot, after manually reboot from web interface.

    @PeterUK , i will try to wireshark DHCP at next week. But i can only wireshark switches with new firmware. All switches, that we use, have latest firmware. Downgrade is imposible, because they all used in production.

  • Zyxel_Melen
    Zyxel_Melen Posts: 1,629  Zyxel Employee
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    Hi @andyvolk,

    Based on your screenshot, I found some devices, like "FD:7C" & "0D:E5", which look like they have the same problem. Since the other devices have the same problem, this problem might not relate to GS1200-8 only.

    For the wireshark DHCP part, please also try to enable the port mirror for the uplink port of GS1200. This allows us to check what packet the switch receives.

    Zyxel Melen

  • PeterUK
    PeterUK Posts: 2,706  Guru Member
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    edited January 8

    So it looks like the switch does DHCP by broadcast flag but normally the switch should do discover offer request ack by broadcast flag but then try to renew by unicast then it tries by broadcast with the broadcast flag which maybe the reason its failing if the switch is not accepting the renew?

  • andyvolk
    andyvolk Posts: 11
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    FD:7C is SIP phone, which was at wrong VLAN and can't receive IP. I fixed it.
    0D:E5 is Mikrotik 4011 interface, which answer DHCP requests

  • Zyxel_Melen
    Zyxel_Melen Posts: 1,629  Zyxel Employee
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    Hi @andyvolk,

    Thanks for your feedback. Please help to get the wireshark DHCP packets and share them with me. In addition, we need the packets captured on Mikrotik router and the GS1200. You may use the port mirror function on GS1200 to mirror the uplink port to capture the packet.

    Zyxel Melen

  • andyvolk
    andyvolk Posts: 11
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    Ok. I need some time for Wireshark. Once I get access to the devices I will try to grab the traffic.

  • Zyxel_Melen
    Zyxel_Melen Posts: 1,629  Zyxel Employee
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    Hi @andyvolk

    Thanks for your feedback. Please take your time.

    Zyxel Melen

  • andyvolk
    andyvolk Posts: 11
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    Hi.
    Currently, i can't do wireshark on switch because all ports on them used and are in production.
    i try setup additional Mikrotik before problematic Zyxel, and grab traffic from it. In this setup DHCP traffic from Zyxel is missing. Devices behind Zyxel works OK.

    Need to notice, that trouble is on two offices, and two uses VLAN.
    On other objects, which don't use VLANs there is no such problem.
    Maybe it because VLAN.

    In attachment pcap file which i receive from router.

  • PeterUK
    PeterUK Posts: 2,706  Guru Member
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    edited February 12

    The problem is Option: (50) Requested IP Address (0.0.0.0)

    So looks like Zyxel DHCP fine at the start not sure if it renews then the above happens and goes in a loop NAK sent back to Zyxel I would think should resets the DHCP client to start over but then why is it Requested IP Address 0.0.0.0 in the first place? or should the DHCP server give a new IP and not send a NAK?

  • andyvolk
    andyvolk Posts: 11
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    I also tried to set DHCP server with clear config directly before looped Zyxel, exclude other devices (Pure mikrotik device with DHCP server and Zyxel switch), and still no receive any address, and no any DHCP traffic too.