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I have a HP ProCurve A7102DL router which has eth1 and eth2 interfaces. I currently have eth1 set as my WAN and eth2 as my LAN side. My eth2 has three IP address assigned to it which are A.A.A.1, B.B.B.1, & C.C.C.1. The LAN side IP addresses all show up in the routing table correctly as A.A.A.0 255.255.255.0 and so on. My eth1 address is my static IP assigned by my ISP. The IP they assigned is X.X.X.252 with a subnet of 255.255.255.248. That connection shows up in my routing table as X.X.X.248. I was wondering why it is changing the IP address of the connected interface and if this is something I should be concerned with.

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1 Answer 1

up vote 1 down vote accepted

The routing table is showing the network-ID, not the interface IP address. (Same as your first case, where your ip is a.a.a.1 and network is a.a.a.0/24).

For example:

$ ipcalc 10.0.0.252/29
Address:   10.0.0.252           00001010.00000000.00000000.11111 100
Netmask:   255.255.255.248 = 29 11111111.11111111.11111111.11111 000
Wildcard:  0.0.0.7              00000000.00000000.00000000.00000 111
=>
Network:   10.0.0.248/29        00001010.00000000.00000000.11111 000
HostMin:   10.0.0.249           00001010.00000000.00000000.11111 001
HostMax:   10.0.0.254           00001010.00000000.00000000.11111 110
Broadcast: 10.0.0.255           00001010.00000000.00000000.11111 111
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Thank you that makes more sense to me. –  jer.salamon Jan 11 '13 at 17:57

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