Should ipaliased IP addresses answer broadcast packets?

From: Rob Fulton (rob@cow-frenzy.co.uk)
Date: Sun Jan 20 2002 - 07:12:31 EST


Hi,

I am presently setting up a server for a gamin event I am planning to run. I
have a Linux box running Debian and a 2.2.20 custom kernel. I have IP alias
compiled in and can create the aliased interfaces. My ifconfig output as
shown below proves this :

eth0 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:26568 errors:0 dropped:0 overruns:0 frame:0
          TX packets:37868 errors:0 dropped:0 overruns:3 carrier:0
          collisions:0 txqueuelen:100
          Interrupt:5 Base address:0xe00

eth0:0 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.110 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:5 Base address:0xe00

eth0:1 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.111 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:5 Base address:0xe00

eth0:2 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.112 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:5 Base address:0xe00

eth0:3 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.113 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:5 Base address:0xe00

eth0:4 Link encap:Ethernet HWaddr 00:40:95:30:73:83
          inet addr:192.168.0.114 Bcast:192.168.0.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          Interrupt:5 Base address:0xe00

lo Link encap:Local Loopback
          inet addr:127.0.0.1 Mask:255.0.0.0
          UP LOOPBACK RUNNING MTU:3924 Metric:1
          RX packets:33 errors:0 dropped:0 overruns:0 frame:0
          TX packets:33 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0

The game client has however been unable to connect to the server, using
tcpdump I can see the request from the server going to the broadcast address
as shown below.

11:53:01.315928 kryten.1480 > 255.255.255.255.27015: udp 16

The server however, never replies. When pinging the broadcast address, the
ip address of the interface replies as shown below but none of the aliased
addresses reply to the broadcast ping. Is this normal behaviour? Should
aliased addresss reply to pings?

64 bytes from 192.168.0.101: icmp_seq=2 ttl=255 time=0.0 ms

One other observation that may or may not effect this is that there is no
/proc/net/aliases file. Aliases is compiled into the kernel rather than as a
module.

Thanks for any help

Rob Fulton

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