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mellman_119375's avatar
mellman_119375
Icon for Nimbostratus rankNimbostratus
Apr 25, 2013

b arp vs arp and how bigip uses it.

Hello.

 

I noticed that b arp and arp are two different things however the commands and output can misslead.

 

b arp shows IP-arp resolution for BIGIP or better said (here and leter) LTM logic right while arp shows the table for linux system.

 

Now. Assume I create pool with nodes which will have simple icmp monitor.

 

That means bigip will "request" for availability of it's nodes in intervals.

 

Obviously to get IP reached it has to know address which will be resolved by arp.

 

Which arp table will be used by LTM then?

 

 

basic
getting started
new to f5

7 Replies

  • mellman_119375's avatar
    mellman_119375
    Icon for Nimbostratus rankNimbostratus
    Apr 25, 2013

    Thank you. That's what I supposed also.

     

    What can be the reason that:

     

    b arp shows one node address incomplete while arp shows it complete and besides ping from command line works fine?

     

  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    Apr 25, 2013
    b arp displays ARP entries learnt and available via the TMM switch interface (as used by LTM), arp via the management interface.

     

     

    So, ping will work if the management interface is used and has connectivity to the node but this is entirely separate to the ICMP monitor which will use the LTM routing table and TMM switch interfaces.

     

     

    This is probably a routing issue. Do you have a suitable LTM route (i.e visible in the GUI) configured for the network the node is on (assuming it's not local)?
  • mellman_119375's avatar
    mellman_119375
    Icon for Nimbostratus rankNimbostratus
    Apr 26, 2013
    Posted By What Lies Beneath on 04/25/2013 08:33 AM

     

    b arp displays ARP entries learnt and available via the TMM switch interface (as used by LTM), arp via the management interface.

     

     

    So, ping will work if the management interface is used and has connectivity to the node but this is entirely separate to the ICMP monitor which will use the LTM routing table and TMM switch interfaces.

     

     

    This is probably a routing issue. Do you have a suitable LTM route (i.e visible in the GUI) configured for the network the node is on (assuming it's not local)?

     

     

    That's fine. I understand.

     

    For the second issue.

     

    This is weird as the node with IP is in the same network - where self ip of big is.

     

  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    Apr 26, 2013
    Are you sure the node is cabled correctly? In the correct VLAN etc? The arp output for the Linux shell is probably just showing you the MAC of the default gateway as I assume the management interface is not in the same network as the node.
  • mellman_119375's avatar
    mellman_119375
    Icon for Nimbostratus rankNimbostratus
    Apr 30, 2013

    Hi yes it is the correct vlan. Cabling should be ok as well.

     

    Could you please ensure me that my understanding of management interface is the same. That separate management interface for managing box.

     

  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    Apr 30, 2013
    The management interface will not be used for LTM functions.

     

     

    Can you trying looking at it the other way. Does the node have an ARP entry for the F5?