Brocade ICX 6610 - what does dhcp-client enable do?

Discussion in 'Networking' started by kur1j, Nov 19, 2019.

  1. kur1j

    kur1j New Member

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    I know what DHCP is, but I don't understand what its context is on a switch/router for these ports. I was expecting to be able to plug this switch up to my router that is providing DHCP, see the new lease captured by the Brocade and connect to the port with ssh, but the 6610 isn't getting an IP.

    Disabling or re-enabling the DHCP client

    What is the "ip dhcp-client enable" doing in the context of these ports?
     
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  2. fohdeesha

    fohdeesha Kaini Industries

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    exactly what it says, it runs as a dhcp client to allow the switch to pull an IP. It's on by default. If it's not pulling an IP it could be a number of reasons, ancient firmware, an old config that disabled the dhcp client, or statically assigned IPs. Also SSH will not be running until you generate a keypair and either config a username/pass or disable ssh authentication. You need to follow the update and config guide from the main ICX thread which covers all this: FCX / ICX6610 - Fohdeesha Docs
     
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  3. kur1j

    kur1j New Member

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    So that’s what I assumed it does but it doesn’t seem to be working. I checked what you mentioned and I have a recent version of firmware. But doesn’t seem to be pulling an IP on that interface when I plug it in.

    I’m working from the console port at the moment so ssh isn’t coming into play since it seems the system isn’t pulling an IP anyways (at least I don’t see a new lease from my DHCP server, and show ip addresses doesn’t show any either).

    ICX 6610

    The config is basically a factory default config after I updated.

    I can set an IP address manually on an interface plug a cable in and can ping it from my workstation. It seems to add “no ip dhcp-client enable” automatically which I assume is for obvious reasons that it’s set as static.

    If i go in and do “ip dhcp-client enable” the config doesn’t show that it any longer in the configuration (after removing the manual IP).

    Something I’m missing?
     
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  4. fohdeesha

    fohdeesha Kaini Industries

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    I don't think that with layer 3 firmware the ports will pull an IP via dhcp unless the vlan they are in has been assigned a router-interface to actually have an IP (as covered in the guide), without that there's no layer 3 interface on the switch to have an address. The management port should grab one regardless if I remember right
     
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  5. fohdeesha

    fohdeesha Kaini Industries

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    I would also remove add-host-route-first, reboot, and try again, it's possible having l3 config like this makes it start ignoring DHCP. What made you add it to your config in the first place? It just makes it buffer TCP handshakes until ARP is resolved instead of dropping them until ARP has a live record (and only affects outbound control plane generated traffic to hosts that aren't in the ARP table yet), I can't think of a regular home application in which you'd need to change said behavior
     
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    Last edited: Nov 20, 2019
  6. kur1j

    kur1j New Member

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    I didn’t change the add-host-route as far as I know unless it got changed inadvertently when I was making changes to the ip of these interfaces or got added automatically via some other command.

    I’ll try those suggestions and see what happens and let you know.

    Thanks!
     
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  7. kur1j

    kur1j New Member

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    I think that worked. It seems to be grabbing an IP address now. Much appreciated. I would have never assumed that was causing the issue.

    Code:
    interface ethernet 1/3/8
     ip address 192.168.0.215 255.255.255.0 dynamic
     speed-duplex 10G-full
    
     
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  8. kur1j

    kur1j New Member

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    Ok I'm at a total loss here...I thought that if the system gets an IP it should be accessible where I could manage this thing over the network instead of having to have the computer hooked up to the console port.

    I have it hooked up like this...

    desktop --> Brocade 6610 --> main network switch --> router

    If the brocade picks up an IP address from DHCP my desktop loses any connectivity what so ever to anything. If I remove the IP address and make the uplink port to the main switch "no ip dhcp-client enable" disabling the DHCP address my desktop will connect correctly.

    I was just following these instructions here Configuring an IP address for the device and its the same thing. It will kick my desktop offline and I can't do anything until I remove the IP on the uplink interface. I can't ping anything at all with my desktop when that happens.

    I assume what its doing is causing the brocade switch to want to act like a router? But I feel I still should be able to ping the unit seeings how its still on the same subnet (192.168.0.0/24).

    All I want to do is give the unit an IP address to make it accessible so I can make it over the network.
     
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  9. fohdeesha

    fohdeesha Kaini Industries

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    that link is how you assign an IP to a switch running layer 2 firmware, and you are running layer 3. I would skip DHCP altogether, that's not how these were meant to operate (and can't think of any use cases or environments where they are). Give it a static IP, following the same guide everyone else here has without a single issue: FCX / ICX6610 - Fohdeesha Docs

    That's exactly what the STH guide has you do, that more than 200 people have used without issue now in the main ICX thread - I would stop resorting to random google result articles and just use the same guide everyone else has - reading more docu is great, but I would ensure you at least have the basics down first
     
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  10. kur1j

    kur1j New Member

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    Thanks. Well, I went down the rabbit hole of trying to get the management port to provide management access. Doing that, I ran into the second bullet of this article. How the management port works

    Then I was simply trying to just get DHCP to assign the IP addresses to the interface so I could just look up the IP address (or just use the hostname) that the DHCP gave it.

    that was my logic for it anyways.

    I wasn't actively avoiding your guide, but was just trying to adapt it slightly and I thought logically that just assigning an IP address to a port was going to accomplish the same thing (that article I mentioned stated "follow this for layer 3 switch") as making a ve since they were both on the same VLAN.

    Your guide does work, and I have it work now, so thank you. Guess I have some more reading to do to understand why its functioning the way it is. Appreciate the help.
     
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  11. fohdeesha

    fohdeesha Kaini Industries

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    note the "to a router port" of the guide's "to a router port on a device running Layer 3 software." instruction - eg a port running layer 3 firmware behaves much differently when assigned an IP directly, it basically becomes a VE and other ports are not going to be able to access it like you think (and traffic on said port will only hit the VE, and expect to get routed to another one)

    the management port is indeed totally isolated, and assigning an IP to it works like you'd expect (eg you'll only be able to access it when plugged into the management port directly)
     
    #11
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