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PIX 501: Inside/Outside IP Addressing

Posted on 2006-11-17
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Hello!

Just to warn you before reading this: I barely know enough about subnetting to get by so excuse any stupid questions please. Anyway, I am trying to set up two network segments separated by my PIX. When I try and change the inside IP of the PIX I get an error:

pixfirewall(config)# show ip
System IP Addresses:
        ip address outside 172.20.4.9 255.255.252.0
        ip address inside 192.168.1.1 255.255.255.0
Current IP Addresses:
        ip address outside 172.20.4.9 255.255.252.0
        ip address inside 192.168.1.1 255.255.255.0
pixfirewall(config)# ip address inside 172.20.6.1 255.255.252.0
Sorry, not allowed to enter IP address on same network as interface 0

With a subnet mask of 255.255.252.0 isn't 172.20.4.X on a different subnet as 172.20.6.X? Why is there a conflict?

Thanks in advance.

Mike
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Question by:jbisordi
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Keith Alabaster earned 1000 total points
ID: 17967421
You have used a 255.255.252.0 mask which includes both the outside ip range 172.20.4.0 and the suggested inside ip range of 172.20.6.0, you cannot do this. If you want to use these addresses then change the subnet mask to 255.255.255.0

the 255.255.252.0 mask = all addresses from 172.20.4.0 - 172.20.7.255
the 255.255.255.0 mask = 172.4.0 - 172.20.4.255

alternatively you could use 255.255.254.0

the 255.255.254.0 mask = 172.20.4.0 - 172.20.5.255

Whichever you choose, make sure that ALL devices on the subnets are changed to reflect the same subnet masks.

Regards
Keith
                                   
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by:Keith Alabaster
ID: 17967908
Thank you :)
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