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My Windows router is set up to use 192.168.16.1/24 as its IP address. I have just added a new IP address: 192.168.18.1/24. However, I am unable to ping this new IP address from my desktop. I have added 192.168.18.2/24 to my desktop, which is unable to access

I am also unable to ping 192.168.18.1 from within the server. I can ping 192.168.16.1 with no problems. I have also discovered that I am unable to ping 127.0.0.1 from this machine. This leads me to believe there is a firewall getting in the way. Can anyone suggest a way to debug this? I have tried completely disabling the Windows firewall, but this doesn't seem to have any effect.

As an aside, can you confirm that my use of the slash notation is correct? I believe that saying 192.168.16.1/24 is the same as saying 192.168.16.1 with a subnet mask of 255.255.255.0. What is the correct name for this notation?

Thank you for your time.

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migrated from serverfault.com Nov 25 '10 at 16:50

This question came from our site for system and network administrators.

    
Try disabling and then re-enabling your network connection(s). –  Khaled Nov 25 '10 at 16:40
    
Do you have 127.0.0.1 defined in c:\windows\system32\drivers\etc\hosts? Are you trying to assign two IP addresses to a single network card in your PC? How are you adding a second IP to your router? Do you have routes set to send traffic to .16 and .18 subnets? –  dmah Nov 25 '10 at 17:15
    
@dmah: 1) /etc/hosts can mess up the name localhost but never the address 127.0.0.1. 2) Multiple addresses per interface are valid. –  grawity Nov 25 '10 at 18:16

2 Answers 2

All working address should be pingable. Try using ipconfig to list all your configured addresses.

192.168.16.1/32 is the same as address 192.168.16.1. 192.168.16.1/24 is a network and usually defined as 192.168.16.0/24. Address 192.168.16.1 is usually on a network specified as 192.168.16.0/24. The router for this network is usually found at 192.168.16.1 or 192.168.16.254. Addresses 192.168.16.0 and 192.168.16.255 have special meaning and are not usable as host addresses. The suffix /31 does not specify a usable network, as both addresses are special addresses. THe suffix /30 specifies the smallest usable network (2 host addresses).

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What kind of router do you have? Just a standard in-home router found at Walmart or Best Buy? If that is the case. I am not sure you can 2 different networks or vlans on a single in-home router.

However, try setting subnet mask to 255.255.252.0 on your computers. This would make a single network -- 192.168.16.0/22. This network would cover every IP between 192.168.16.0 to 192.168.18.255. With the valid host IPs (IPs you can configure your computers with), anything between 192.168.16.1 to 192.168.18.254. That is because the first IP (192.168.16.0) and and last IP(192.168.18.255) of a network can not be used. First IP is used to define the network itself. While the last IP is used for network broadcasts.

Don't forget to set a default gateway that points to your router. Just like BillThor said, the standard is normally the first valid host IP of the network, 192.168.16.1, or the last valid host IP, 192.168.18.254.

I'll change my answer if more information is provided.

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