funny ECMP

Ingo Flaschberger if at xip.at
Mon Aug 23 00:04:44 UTC 2010


Hi,

System:
FreeBSD 8.1-STABLE amd64

ifconfig em1 10.11.11.175/24
ifconfig em1 alias 10.13.13.90/24
route add 10.13.13.95/24 10.11.11.1

ping 10.13.13.90

dump at: 10.13.13.95
23:50:21.877426 00:90:0b:0c:16:06 > 00:01:02:1e:e3:64, ethertype IPv4 (0x0800), length 98:
 	10.11.11.175 > 10.13.13.95: ICMP echo request, id 775, seq 122, length 64
23:50:21.877431 00:01:02:1e:e3:64 > 00:90:0b:17:6e:6f, ethertype IPv4 (0x0800), length 98:
 	10.13.13.95 > 10.11.11.175: ICMP echo reply, id 775, seq 122, length 64

-> wrong outgoing interface ip
-> 00:90:0b:0c:16:06 is the mac from 10.13.13.1
-> local (connected) should be before static route

00:90:0b:0c:16:06: 10.11.11.1
00:90:0b:17:6e:6f: 10.11.11.175 / 10.13.13.90
00:01:02:1e:e3:64: 10.13.13.95

just more:
ping -S 10.13.13.90 10.13.13.95

23:57:28.803763 00:90:0b:0c:16:06 > 00:01:02:1e:e3:64, ethertype IPv4 (0x0800), length 98:
 	10.13.13.90 > 10.13.13.95: ICMP echo request, id 9991, seq 118, length 64
23:57:28.803772 00:01:02:1e:e3:64 > 00:90:0b:17:6e:6f, ethertype IPv4 (0x0800), length 98:
 	10.13.13.95 > 10.13.13.90: ICMP echo reply, id 9991, seq 118, length 64

-> 00:90:0b:0c:16:06 is the mac from 10.13.13.1
-> local (connected) should be before static route

Kind regards,
 	ingo flaschberger


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