9
edits
Changes
Added examples of arpflux.
For example, you want some of your VE's to always use eth3, and some to use eth4. But none of the VE traffic should use eth0, which is reserved for use by the HN only. This makes sense if you have VE's that may generate or receive a lot of traffic and you don't want your remote administration of the server over eth0 to degrade or get blocked because of this.
To make this clear we'll use the following HN configuration. We'll also have another system to act as the client.
{| align="center" border="1" cellpadding=5
! System !! Interface !! MAC Address !! IP Address
|-
| HN || eth0 || 00:0c:29:b3:a2:54 || 192.168.18.10
|-
| HN || eth3 || 00:0c:29:b3:a2:68 || 192.168.18.11
|-
| HN || eth4 || 00:0c:29:b3:a2:fe 5e || 192.168.18.12|-| client || eth0 || 00:0c:29:d2:c7:aa || 192.168.18.129
|}
=== HN ARP Flux ===
The first issue is ARP flux. Any client on the network broadcasting an ARP "who has" message for any of these addresses will receive replies from all three interfaces. This results in IP addresses that float between three MAC addresses, depending on which response a client accepts first.
For example, the following is a tcpdump capture from executing <pre>ping -c2 192.168.18.10</pre> from another system on the network.
<pre>
00:0c:29:d2:c7:aa > ff:ff:ff:ff:ff:ff, ARP, length 60: arp who-has 192.168.18.10 tell 192.168.18.129
00:0c:29:b3:a2:5e > 00:0c:29:d2:c7:aa, ARP, length 60: arp reply 192.168.18.10 is-at 00:0c:29:b3:a2:5e
00:0c:29:b3:a2:54 > 00:0c:29:d2:c7:aa, ARP, length 60: arp reply 192.168.18.10 is-at 00:0c:29:b3:a2:54
00:0c:29:b3:a2:68 > 00:0c:29:d2:c7:aa, ARP, length 60: arp reply 192.168.18.10 is-at 00:0c:29:b3:a2:68
00:0c:29:d2:c7:aa > 00:0c:29:b3:a2:5e, IPv4, length 98: 192.168.18.129 > 192.168.18.10: ICMP echo request, id 32313, seq 1, length 64
00:0c:29:b3:a2:54 > 00:0c:29:d2:c7:aa, IPv4, length 98: 192.168.18.10 > 192.168.18.129: ICMP echo reply, id 32313, seq 1, length 64
00:0c:29:d2:c7:aa > 00:0c:29:b3:a2:5e, IPv4, length 98: 192.168.18.129 > 192.168.18.10: ICMP echo request, id 32313, seq 2, length 64
00:0c:29:b3:a2:54 > 00:0c:29:d2:c7:aa, IPv4, length 98: 192.168.18.10 > 192.168.18.129: ICMP echo reply, id 32313, seq 2, length 64
00:0c:29:b3:a2:54 > 00:0c:29:d2:c7:aa, ARP, length 60: arp who-has 192.168.18.129 tell 192.168.18.10
00:0c:29:d2:c7:aa > 00:0c:29:b3:a2:54, ARP, length 60: arp reply 192.168.18.129 is-at 00:0c:29:d2:c7:aa
</pre>
The ARP "who has" message generated replies from all three MAC addresses on the HN. In this case the client took the MAC address for eth4. The three ICMP messages are then sent to eth4, but all the replies com from eth0. Normally this behavior isn't a problem, though it may generate some false alarms for a network monitor as it appears someone could be executing a man in the middle attack.
The following output is from executing this command on the HN.
<pre>sysctl -a | grep net.ipv4.conf.*.arp</pre>
<pre>
net.ipv4.conf.venet0.arp_accept = 0
net.ipv4.conf.venet0.arp_ignore = 0
net.ipv4.conf.venet0.arp_announce = 0
net.ipv4.conf.venet0.arp_filter = 0
net.ipv4.conf.venet0.proxy_arp = 0
net.ipv4.conf.eth4.arp_accept = 0
net.ipv4.conf.eth4.arp_ignore = 0
net.ipv4.conf.eth4.arp_announce = 0
net.ipv4.conf.eth4.arp_filter = 0
net.ipv4.conf.eth4.proxy_arp = 0
net.ipv4.conf.eth3.arp_accept = 0
net.ipv4.conf.eth3.arp_ignore = 0
net.ipv4.conf.eth3.arp_announce = 0
net.ipv4.conf.eth3.arp_filter = 0
net.ipv4.conf.eth3.proxy_arp = 0
net.ipv4.conf.eth0.arp_accept = 0
net.ipv4.conf.eth0.arp_ignore = 0
net.ipv4.conf.eth0.arp_announce = 0
net.ipv4.conf.eth0.arp_filter = 0
net.ipv4.conf.eth0.proxy_arp = 0
net.ipv4.conf.lo.arp_accept = 0
net.ipv4.conf.lo.arp_ignore = 0
net.ipv4.conf.lo.arp_announce = 0
net.ipv4.conf.lo.arp_filter = 0
net.ipv4.conf.lo.proxy_arp = 0
net.ipv4.conf.default.arp_accept = 0
net.ipv4.conf.default.arp_ignore = 0
net.ipv4.conf.default.arp_announce = 0
net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.default.proxy_arp = 0
net.ipv4.conf.all.arp_accept = 0
net.ipv4.conf.all.arp_ignore = 0
net.ipv4.conf.all.arp_announce = 0
net.ipv4.conf.all.arp_filter = 0
net.ipv4.conf.all.proxy_arp = 0
</pre>
If all three network interfaces are on different IP networks (such as 10.x.x.x, 172.16.x.x, 192.168.x.x) then executing the following will work:
</pre>
<pre>
</pre>
=== Adding some VE's ===
<pre>
</pre>
TODO: Discuss approach of <code>ip rule ...</code> and <code>ip route ...</code>.
[[Category:HOWTO]]
[[Category:Networking]]
