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strange behavior on juniper ARP table when host adds new ip address to same interface

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  • 1.  strange behavior on juniper ARP table when host adds new ip address to same interface

    Posted 11-01-2017 06:57

    I have a juniper SRX340 running as default gateway, I have a linux server (virtual machine actually) running debian 8.

    juniper ip: 192.168.1.1 Debian ip: 192.168.1.101 (eth0)

    I would like to add more ip addresses on my Debian box, so I create a new sub-interface and give it an ip

    debian ip2: 192.168.1.102 (eth0:1)

    when I do this, I can not ping the juniper box from the new ip address.. and juniper can not ping the new ip address.

    I CAN ping other hosts on the same network from the new ip address and they can ping it... all is well.

    so.. the new ip address can not see juiper box, and the juniper box can not see the other ip... so then I try something.

    I change the ip address of eth0 to be 192.168.1.102 and now I can ping the juniper box, and the juniper box can ping me back.

    then I change it back so that eth0: 192.168.1.101 and eth0:1: 192.168.1.101 and now juniper can ping both ip addresses, and both ip addresses can ping juniper.

    so.. then I take the test further and add a 3rd interface eth0:2 and give it the ip 192.168.1.103 and I have the same problem... I can not see juniper, and juniper can not see new ip...

    again, if I change the original eth0 to use 103 as ip first, then go back, it works again.. this is very confusing.

    any suggestions what is going on here?

    junos version 15.1X49-D100.6



  • 2.  RE: strange behavior on juniper ARP table when host adds new ip address to same interface
    Best Answer

    Posted 11-01-2017 11:07
    can u pl check following?
    1. are u learning mac add of subinterface during problematic condition?
    2. Is the mac address of newly created subinterfaces are same? (excuse me as i do not have much knowlege for debian)..
    3. if u are not learning the mac and arp during problem of new subinterfaces, can u add static arp on srx with correct interface and check?



  • 3.  RE: strange behavior on juniper ARP table when host adds new ip address to same interface

    Posted 11-02-2017 01:07

    Thank you!

    1) not sure what you mean

    2) the mac address is the same on all ip on same interface also in debian

    3) adding a static arp worked! that is the trick I will use! thanks you so much! did not know I could do that.