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I want to setup an 881 router such that it gets its IP address via DHCP. But I also want to setup a backup IP address in case it failed to obtain an IP via DHCP.

I tried setting secondary IP address but the moment I configured ip address dhcp, the config for secondary IP disappeared.

Is there a way to setup fallback IP?

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  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Commented Aug 7, 2017 at 20:02

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You either get to have DHCP, or you get to use fixed addresses, but you don't get to use both, secondary address, or not.

Unless you are getting an IP address via DHCP from an ISP (in which case, I don't think a static address would work, anyway), I don't normally like the idea of using DHCP to configure network infrastructure devices. There is just too much that can go wrong and isolate part of the network.

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  • The reason is I need to move this router around. On one network, it will get IP via DHCP. On another, I need it on static.
    – some user
    Commented Feb 25, 2016 at 19:57
  • You will need to configure it for each network. DHCP is an "either... or..." choice.
    – Ron Maupin ♦
    Commented Feb 25, 2016 at 20:03
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    The other option is to configure one interface for DHCP, and a different one for static addressing. Just connect the correct interface for the network to which you connect.
    – Ron Maupin ♦
    Commented Feb 25, 2016 at 20:05
  • That would work but then my static NAT configuration would get complications. :(
    – some user
    Commented Feb 25, 2016 at 21:30
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Create a loopback interface and add a static ip for it.

Loopvack interfaces are never down and can be reached everytime.

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  • This answer doesn't actually help with the situation since you would need to go through the interface in question in order to get to the loopback.
    – Ron Maupin ♦
    Commented Feb 25, 2016 at 20:04

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