Re: How to address 'ping -I <interface>' failure

Thank you for responding, I appreciate it.  That is most interesting and would explain what I'm seeing, is this "little specific thing" documented somewhere?  How did you find this out?

----- Original Message -----
From: "Anton Danilov" <[email protected]>
To: "Leroy Tennison" <[email protected]>
Cc: "lartc" <[email protected]>
Sent: Wednesday, February 14, 2018 1:58:20 AM
Subject: Re: How to address 'ping -I <interface>' failure

Hello. 
There is a little specific thing with "-I <iface>" usage in the ping tool. 
When you specify an interface name in the -I option, the ping tool work as if the destinated host is in directly-connected segment. 
If you run the tcpdump, you will see the arp requests to resolve the destinated ip address. 
So, use the -I option with interface names only to ping directly attached host or if you have proxy-arp enabled gateway. 


On 22 January 2018 at 19:55, Leroy Tennison < [ mailto:[email protected] | [email protected] ] > wrote: 


Background: 
2 wan interfaces - call them 12.14.16.18 on eth0 (not the issue) and 98.100.102.105 on eth1 (both /29), 
'ping -I 98.100.102.105 [ http://google.com/ | google.com ] ' works but 'ping -I eth1 [ http://google.com/ | google.com ] ' returns 'From 98.100.102.105 icmp_seq=1 Destination Host Unreachable' 

'cat /etc/iproute2/rt_tables' shows (leaving out commented lines) 

255 local 
254 main 
253 default 
0 unspec 
1 fbr 
3 dsl 

ip rule shows (leaving out default and ipsec) 

10000: from all fwmark 0x1/0xff lookup fbr 
10002: from all fwmark 0x3/0xff lookup dsl 
20000: from 12.14.16.18 lookup fbr 
20000: from 98.100.102.105 lookup dsl 

ip route show table dsl has (leaving out OpenVPN and other local non-Internet interfaces) 

default via 98.100.102.108 dev eth1 src 98.100.102.105 
[ http://98.100.102.104/29 | 98.100.102.104/29 ] dev eth1 proto kernel scope link src 98.100.102.105 
98.100.102.108 dev eth1 scope link src 98.100.102.105 

I'm just beginning to learn about multiple routing tables so I tried the following suspecting it wouldn't work (and it didn't): 'ip rule add from eth1 table dsl' and got 'Error: ??? prefix is expected rather than "eth1" ' 

What do I need to do to get 'ping -I eth1 [ http://google.com/ | google.com ] ' to work? Thanks for your help. 


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-- 
Anton.