Secondary Interface Question

Unanswered Question
Apr 22nd, 2010


    I have a client who I am assisting with some network issues.  The company that manages their network has several private networks tunneled for them to access devices remotly.  My question is with the config a particular interface on their router which i will include below.  I have always understood that adding numerous secondary interfaces is not smiled upon and can essentially create one huge broadcast domain...but I just want to get some other professional opinions.  This is for a ISP so I am going to summarize the IP space to protect the identify of my client but if you would like to see any config I don't include please let me know and I will be happy to provide it.  So what would your opinions be on this interface configuration?

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  description to Equipment
  ip address Public IP secondary
  ip address secondary
  ip address secondary
  ip address Public IP secondary
  ip address secondary
  ip address secondary
  ip address secondary
  ip address secondary
  ip address secondary
  ip address Public IP

I have this problem too.
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Giuseppe Larosa Thu, 04/22/2010 - 23:52

Hello Kyle,

I would recommend to move to a scenario where multiple Vlans are used one per each subnet.

This can be possible if the LAN interface connects to a LAN switch that you can configure as a L2 trunk.

This allows to provide broadcast control and to confine broadcasts in each IP subnet.

An high level of broadcast traffic affect also end user devices not only the router and other network devices.

So current scenario is not efficient.

If new IP subnets need to be added a new Vlan can be created on the switch and a new subinterface can be configured on the router side.

if this is not possible because L2 switches are unmanaged or do not support multiple Vlans and trunking I would consider in the long term to replace them with manageable, multi vlans capable, switches.

Hope to help



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