Hi,
I'm writing a tool for network topology discovery, based on SNMP. I
installed the UCD-SNMPd on my Linux-routers, because I want to read the
ARP-table of the different routers, to get a list of connected hosts. The
SNMPd reads the /proc/net/arp table to get his information. Because an
IP-address is only active in the ARP-table for a small period of time, I
first send an ICMP-packet to all the possible IP-addresses and then I
check the ARP-table.
The problem is that in Linux also non-active IP-addresses show up in the
ARP-table with MAC-address equal to zero. (See the example at the end of
this mail) This causes a rather big delay using the SNMP-protocol. We also
have a Cisco 7500 router, and there you only get the active IP-addresses
and their MAC-addresses (all different from zero)
Is there an option to avoid this large ARP-tables, or is where do I have
to change the kernel source ??
Thanks for your help,
Kurt Glazemakers
Kurt.glazemakers@rug.ac.be
Example of a large ARP-table
IP address HW type Flags HW address Mask
Device
10.10.184.116 0x1 0x0 00:00:00:00:00:00 *
eth0
10.10.184.80 0x1 0x2 08:00:20:86:DB:B8 *
eth0
10.10.184.61 0x1 0x2 00:50:BA:C3:79:1C *
eth0
10.10.184.25 0x1 0x0 00:00:00:00:00:00 *
eth0
10.10.184.117 0x1 0x2 00:80:C8:C9:65:51 *
eth0
10.10.184.81 0x1 0x2 08:00:20:93:BF:63 *
eth0
10.10.184.60 0x1 0x0 00:00:00:00:00:00 *
eth0
10.10.184.24 0x1 0x0 00:00:00:00:00:00 *
eth0
10.10.184.118 0x1 0x0 00:00:00:00:00:00 *
eth0
10.10.184.82 0x1 0x2 08:00:20:93:C6:C2 *
eth0
...
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