Re: ARP request bug?
Bart Kus <[email protected]>
| Newsgroups | gmane.linux.network.general |
|---|---|
| Message-ID | <[email protected]> |
On 2/18/2011 1:09 AM, Julian Anastasov wrote: > > Hello, > > On Thu, 17 Feb 2011, Bart Kus wrote: > >> Hello Experts, >> >> With 00:04:23:bb:18:56 being a Linux box, it gets a ping request from >> a network device: >> >> 05:50:50.393373 00:0c:db:b5:b7:00 (oui Unknown) > 00:04:23:bb:18:56 >> (oui Unknown), ethertype IPv4 (0x0800), length 60: 172.20.11.3 > >> 192.168.70.1: ICMP echo request, id 43981, seq 1, length 24 >> >> Before replying (even though it could, since it has the MAC as part >> of the ping request) it decides to query for the MAC based on source >> IP of the original ping request: >> >> 05:50:50.402347 00:04:23:bb:18:56 (oui Unknown) > Broadcast, >> ethertype ARP (0x0806), length 42: Request who-has 172.20.11.3 tell >> 192.168.70.1, length 28 >> >> The tell section indicates to "tell 192.168.70.1", but the interface >> on which this came in has an IP of 172.20.11.1. 192.168.70.1 is >> another IP on the Linux router, on a different interface. >> >> Shouldn't the ARP request say "tell 172.20.11.1" instead given ARP is >> an ethernet protocol, incapable of routing to 192.168.70.1? The >> reply to this broadcast never comes back from the other network >> device due to the weird "tell 192.168.70.1" being there. The end >> result is complete ping loss. > > May be what you need is to set on Linux box > /proc/.../arp_announce to 1 or 2. Check > Documentation/networking/ip-sysctl.txt for more info. Perfect! Setting arp_announce to 1 has fixed the issue: 09:15:21.151841 00:0c:db:b5:b7:00 (oui Unknown) > 00:04:23:bb:18:56 (oui Unknown), ethertype IPv4 (0x0800), length 60: 172.20.11.3 > 192.168.70.1: ICMP echo request, id 43981, seq 1, length 24 09:15:21.162059 00:04:23:bb:18:56 (oui Unknown) > Broadcast, ethertype ARP (0x0806), length 42: Request who-has 172.20.11.3 tell 172.20.11.1, length 28 09:15:21.162300 00:0c:db:b5:b7:00 (oui Unknown) > 00:04:23:bb:18:56 (oui Unknown), ethertype ARP (0x0806), length 60: Reply 172.20.11.3 is-at 00:0c:db:b5:b7:00 (oui Unknown), length 46 Thanks! --Bart -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html