Alias IPs causing Gratuitions ARP floods?



  • Hi there,

    I've just configured a pile of Alias IPs on my 2.2.2 install, and it looks like they are all generating lots of gratuitous (?) ARP message. Below is a small excerpt from a package capture.

    I've defined 250 alias IPs on an interface in order to use those for NATing as many subnets out (having a one-to-one mapping between a subnet and an external IP).

    But testing and checking the setup, I can see that there's a ton of ARPs going out. All 250 Alias IPs generate such an ARP message about every 6 seconds…

    Is this normal behaviour??

    Thanks for any pointers!

    15:41:31.733579 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.224 tell 123.45.164.224, length 28
    15:41:31.751203 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.225 tell 123.45.164.225, length 28
    15:41:31.774851 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.226 tell 123.45.164.226, length 28
    15:41:31.798285 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.227 tell 123.45.164.227, length 28
    15:41:31.821773 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.228 tell 123.45.164.228, length 28
    15:41:31.845291 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.229 tell 123.45.164.229, length 28
    15:41:31.868882 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.230 tell 123.45.164.230, length 28
    15:41:31.892280 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.231 tell 123.45.164.231, length 28
    15:41:31.915906 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.232 tell 123.45.164.232, length 28
    15:41:31.939276 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.233 tell 123.45.164.233, length 28
    15:41:31.962637 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.234 tell 123.45.164.234, length 28
    15:41:31.986175 00:26:55:33:c9:e4 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Request who-has 123.45.164.235 tell 123.45.164.235, length 28