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pedinopa_170325's avatar
pedinopa_170325
Icon for Nimbostratus rankNimbostratus
Dec 27, 2017

incomplete ARP

I have a simple virtual F5 install with a single F5 LTM, 1 node, 1 pool, 1 VS. I am having routing issues and noticed in my ARP table there is an incomplete ARP. the address is my gateway, but the HWaddress is incomplete. I saw this same incomplete ARP in the dynamic ARP table in the GUI and tried to delete it (it either came back or did not delete it). Is this incomplete ARP an issue, if so how can I delete it (the gui does not seem to be allowing me or it comes right back)?

 

The weird issue is that the F5 does not appear to be sending traffic to the router.

 

BIG-IP
devops
TMSH

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  • Srini_87152's avatar
    Srini_87152
    Icon for Cirrostratus rankCirrostratus
    Dec 28, 2017

    What is the gateway of sever, normally if server gateway not F5 u cant see arp table, thats expected ..

     

    Thx Srini

     

  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    Dec 28, 2017

    An incomplete ARP means that the BigIUP needs to route via the gateway, and has sent an ARP request to resolve the IP to the physical address, and has not received a response.

     

    Without the ARP entry completing (i.e. A response recieved) the BigIP won't send traffic via the gateway, so yes, this is an issue, and yes this is why you don't see traffic (Assuming the routing tables are correct, etc etc).

     

    Things to check

     

    • Are you really on the same VLAN?
    • Can you see the ARP request leaving the correct interface being broadcast on the VLAN?
    • Can you see the ARP response anywhere? (tcpdump is your indispensable friend here)
    • Going out on a limb, but check there's no firewall, or ip filters on your gateway that would stop the traffic.
  • pedinopa_170325's avatar
    pedinopa_170325
    Icon for Nimbostratus rankNimbostratus
    Jan 03, 2018

    appearently the VM became isolated so when I vmotioned it to another host it began working