10 Replies Latest reply: Jul 11, 2019 9:01 AM by Ian Murphy RSS

    Problem with vlan interface with secondary IP

    Ian Murphy

      We are in the middle of a migration to a Cisco setup and have come across a weird issue. One of the segments which was migrated from the old setup was an office vlan with a subnet for dynamic devices (PCs) and a second subnet for static devices (printers and other stuff).  So, PCs are all 10.23.50.x and printers are all 10.23.55.x

      This has been working fine for years with a non-cisco setup.

       

      The plan is to move the printers to their own vlan, but this will take a while as its a multinational and there are quite a few things which talk to these printers so they're being migrated one by one.

       

      My problem is that some of the printers 'go offline', which is to say that the core switch can no longer ping one or other of the printers and so printing stops.

       

      If I configure a PC with a 10.23.55.x ip address I *can* ping the IP of the printer in question. If I ping it once, the core switch can then also ping it and the servers start printing again.

       

      The issue seems to be that the core switch isn't sending arp packets on the vlan in question for addresses on the secondary IP.

       

      The core switch vlan interface has this configuration:

      interface Vlan100

      description Office Vlan

      ip address 10.23.60.1 255.255.255.0

      ip address 10.23.50.1 255.255.255.0 secondary

      ip address 10.23.55.1 255.255.255.0 secondary

      ip helper-address 10.23.25.171

      no ip redirects

       

      To reiterate: The problem is that a printer with IP, say 10.23.55.123, cannot be reached from either the core switch (10.23.55.1) or from any other device on the network.

      The port associated with the printer shows as being UP.

      Disconnecting and reconnecting the printer network cable  does not change anything.

      If I connect a PC, give it an ip address of 10.23.55.99, and type ping 10.23.55.123, then both core switch and servers are able to see the printer and can print.